Changing the Raw Water Impeller

During the first sea trials of my Nereus at wide open throttle (WOT) it would slowly overheat with the coolant temperature rising from 85-ish degrees up over 100 degrees celcius. If I slowed down and dropped the revs the temperature would again slowly go back down. So either the cooling system was not quite able to pump enough raw water through the heat exchanger or the engine is producing too much heat. I certainly know that the heat exchanger is not blocked since it had been serviced recently.

When purchasing the boat the original owner had told us he’d changed the raw water impeller “a couple of years ago” so I’d purchased a spare impeller but not bothered to change it. The pump is right at the bottom of the engine in the bilge, so it’s a bit of a pain to get too which might also contribute to why it had not been changed.

Anyway I’d run the engine for about an hour on tap (towns) water but only at or just above idle, not under heavy load. So I decided to change the pump for peace of mind. A quick check on the internet and there was a YouTube video from 350vic that gave me some clues as to what was necessary, it didn’t look that hard.

Famous last words.

So first I had to get the pump out of the boat an supported by something that would make it easy to work on. Getting this pump out of the boat was as hard as I feared. There is not quite enough adjustment on the belt tension bolt to allow the belts to slip on and off the pulleys, in fact it hits the sump and if you’re not careful you can punch a hole in it. The bolts that support the lateral load of the pump and hold it in place you just can’t get a ring spanner on, so you have to feel for them using an open ended spanner and shift them a hairs breath, flip spanner, shift, flip spanner. If you’ve ever been forced to do this you will know how slow it is to back the bolt out just half a turn to loosen things off. With a few minor changes to bolt locations this could have been easily serviceable, oh well I do like a good project.

So after a good hour of extraction I managed to get the pump out an into a vice for support, here’s a series of shots that shows the pump being supported, the rear cover having been removed. The impeller didn’t look that bad, there’s a bit of wear on the rear of the vanes but there were no missing vanes and the pump wasn’t hard.

I’m not a fan of using the two screw drivers method for impeller extraction, bruising the face of the pump is just a no no. So for my first time I used vice grips and a slide hammer, being careful not to loose the bronze Woodroffe key. I will certainly be looking at a set of impeller pullers when I have some spare funds in the bank.

Above you can see the backing plate and Woodroffe key, along side the pump housing with the new impeller ready to go back in. So what they don’t tell you about re-assembling these pumps is you’ve got to bend the vanes of the new impeller, while inserting the impeller into the housing, which is offset to one side AND you need to catch the Woodroffe key in one movement. Oh and if you’re supporting the pump in a vice, then make sure the front of the pump is chocked otherwise everything tries to run away.

Needless to say it took me four attempts and a coffee after two to settle my frustration before I managed to get everything aligned and the pump re-assembled. After the first attempt I also marked the Woodroffe key location on the back of the shaft and the impeller so I had a chance of keeping them aligned. It certainly helped to dob a bit of grease on the back of the Woodroffe key and make sure the front edge was slightly down, but not too far down or it would then force the key down and lock it against the pump wall. Sigh.

To prevent the pump running dry I also lubricated the pump walls with a little marine clear grease, I see on some forums people use silicon spray or lanolin, YMMV.

Hooray ! There’s the proof that I did get it back together and didn’t just go and buy a new pump out of frustration. I also dobbed a little “never seize” on the threads of the screws so it should come apart again in a year or so.

It was then just a matter of putting it back into the boat, reversing the disassembly process. Reminding me again why I need to replace the pump mounting assembly.

First Sea Trials

It’s never a good idea to go and place a new boat in the wire and head off into the blue yonder and not expect problems. So to keep things simple I arranged a couple of mates to help and dropped the Nereus into the North Arm of the Port River.

So far so good, it floats ! You’ll have to excuse the state of the pontoon, the local Pelicans have made it their preferred home during the Winter. Once in the water the obligatory “is water coming in” checks were done, it certainly did not have to go back on the trailer.

There was nothing left but to go for it and take things easy. So while cruising slowly towards the Port River the steering and gearbox (ie reverse) were checked, along with lights, bilge pump and the fish finder. Here’s a video of us just pulling away from the pontoon in the obligatory 4 knot zone coming out of the North Arm,.

Once clear of the North Arm we could then head towards Outer Harbour with a bit more power on keeping within the 7 knot limit. During this time we were watching the temperature of the engine and making sure things were going as planned.

Eventually however we were able to open the throttle and put the old girl up onto the plane.

Of course not everything goes to plan and the Log gland decided to spring a leak. It was certainly letting in a reasonable amount of water. A little more grease forced into the gland helped slow things down, but it will certainly need to have the two seals changed when I can find the time to pull it apart.

On the way back up river we managed a couple of high speed runs at wide open throttle (WOT). It was only then we found that the heat exchanger was not quite keeping up and the engine temp started to rise towards 100 degrees Celsius. Simply lifting the throttle and slowing down was enough to drop the temp back to normal. So this will certainly require some further investigation.

Getting out on the water in any boat is a great way to spend an afternoon even better when you can share it with a couple of friends. The trip was certainly successful with only minor issues found and nothing that resulted in us being towed home. We certainly can’t ask for more than that.

At some point I’ll also either capture a video or some photo’s of putting this boat on the trailer. There is a unique catch on the bow that allows the boat to be driven on and caught without having to get out of the boat. The first time we put her back on I was a little preoccupied with not hitting anything so didn’t capture anything. Next time.

Display a PNG Image on small 128×128 OLED LCD

Now that my small OLED display automatically loads the device drivers on boot, it was time to see if I could display an image on my new frame buffer device.

To start with I went looking for a very basic graphics library that would allow me to experiment on frame buffer devices. There is certainly no shortage of libraries to choose from. The library that I settled on was the “Lightweight C 2D graphics API agnostic library with parallelism support” written by grz0zrg. It had both PNG and JPG routines that could output to a simple frame buffer device, being written in C was also a winner.

Flicking through the various examples the quickstart.c file seemed to have nearly everything I needed to display a PNG file on my OLED. Not so long ago a fellow AREG club member shot me some icon files for our club website; one of these icons was 512×512 pixels in size which made it an excellent candidate for shrinking to 128×128 pixels and using it on my OLED.

Downloading the library was as easy as;

$ cd ~
$ git clone

If you don’t have git installed use the relevant apt-get command. The example files can then be found in the following directory;

$ cd ~/fbg/examples 

I then copied the quickstart.c file and hacked on it a little, modifying it like so;

#include <sys/stat.h>
#include <stdio.h>
#include <signal.h>
#include "fbgraphics.h"

int file_exists( const char* filename )
    //define file handle
    FILE *file;

    //attempt to open file read only
    if( (file = fopen(filename, "r")) )
        fclose(file);    // release file handle
        return 1;        // tell someone we found it
        return 0;         //no one home

int main(int argc, char* argv[])
    const char* framebuffer_name = "/dev/fb1";
    const char* logo_filename = "logo.png";

    //check we have a framebuffer to talk to
    struct _fbg *fbg = fbg_setup( (char *)framebuffer_name, 0);
    if (fbg == NULL)
        return -1;

    // make sure logo file exists
    if( !file_exists( logo_filename ))
        printf("File not found: %s\r\n",logo_filename);
        return -2;

    //draw something on the display
    struct _fbg_img *logo = fbg_loadPNG(fbg, "logo.png");
    fbg_clear(fbg, 0);
    fbg_image(fbg, logo, 0, 0);

    //release memory

    return 0;

Which was built with the following command line from within the examples directory;

gcc ../src/lodepng/lodepng.c ../src/nanojpeg/nanojpeg.c ../src/fbgraphics.c display_logo.c -I ../src/ -I. -std=c11 -pedantic -D_GNU_SOURCE -D_POSIX_SOURCE -Wno-unused-value -Wno-unknown-pragmas -O2 -Wall -lm -o display_logo

Hacking upon the Makefile is also not that difficult, I simply added the relevant lines the SRC and OUT sections, then copied the quickstart section and renamed display_logo. There is lots of information about on how to do this on the internet so I’ll not repeat it again unnecessarily.

All I had to do then was place my 128×128 PNG file alongside the display_logo executable (renamed logo.png) and run it… wallah ! I was greeted by the AREG logo on my small OLED display in all of its 128×128 pixel glory; see the image at the top of this post.

So the next trick is to move this to the boot process… So by the looks the plymouth package might be the go, only one way to find out.

Starting a fbtft_device on Boot

After having woken up my small 128×128 OLED display I was wondering how to get it to start automatically each time my rPi booted rather than having to log in and run the commands manually.

It turns out this is rather easy and just required me to edit two files. I’m also glad that these Waveshare OLED displays are effectively compatible with the Freetronics OLED 128×128 graphics display. A big thanks to the Freetronics team for making this driver available for SED1351 chip sets.

So I created the following file with my favourite editor (as root) /etc/modprobe.d/fbtft.conf with the following contents;

options fbtft_device name=freetronicsoled128

What this effectively does is tell the system how to configure the fbtft_device as it boots, much like if we started it with modprobe from the command line i.e used the following command;

sudo modprobe fbtft_device name=freetronicsoled128

So now the system knows how to configure the driver, we need to tell modprobe to load it by placing an entry in the /etc/modules file. So using your favourite editor (as root) edit /etc/modprobe and append the last two lines.

# /etc/modules: kernel modules to load at boot time.
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.


It appears that the SPI bus is a little slow to load if it’s called as a dependency of fbtft_device, which is a classic chicken and egg driver problem. So by starting it manually we make sure it’s available by the time the fbtft driver tries to do anything.

The i2c-dev entry in the same file fires up the i2c bus and was already pre-configured in my system by raspi-config way back when. I’m using it in my project, YMMV. All that is left to do is test it, so reboot and login and run the following command;

$dmesg | grep graphics

We should see something like the following;

[6.128978] graphics fb1: fb_ssd1351 frame buffer, 128x128, 32 KiB video memory, 4 KiB buffer memory, fps=20, spi0.0 at 20 MHz

That tells us that the little OLED display has registered as /dev/fb1 and that it’s ready to go. You can use the con2fbmap trick in my last post to test it’s working.

Now to work out how to get it to throw up an image on boot…

Maple Mini’s & a STM32F103CBT6

I recently found myself at the very limits of what you can ask an Arduino Uno to do, both in terms of flash and speed. I’ve used Atmel AVR processors for nearly 20 years so I know them and their foibles very well.

At work a while back we started using various STM32 processors and that has been somewhat enjoyable, I now like throwing floats around instead of having to resort to fixed point maths and excel for algorithm development. I’d heard that you could run up the Arduino framework on the STM32 platforms so was keen to try it.

So I initially went looking for a well supported board and simply struggled to find one. It seemed that this space had come and gone rather rapidly. Further research showed why, the Chinese clones has effectively decimated this market due to price. I was still keen to give it ago so placed an order for two Maple Mini boards with the STM32F103CBT6 processors on them off eBay for the princely sum of A$20 with free freight. Little wonder everyone abandoned ship in mid 2016.

A big thanks has to go to Leaflabs since they have left all of the circuits, boot-loaders & design files in a GitHub repository here (click).

So what did we have to do to get these working ? It wasn’t as trivial as the Arduino Uno that is for certain.

The first step was to get Windows 7 drivers (yes I know it runs out next year) for the Maple Mini, I found some here (click). I basically hit the green button marked “Clone or Download”, saved the file on my local machine. Extracted the files from the archive to a temp directory, then via the System Manager clicked on the “Maple 003” device that appears, told it I wanted to update the drivers from a specific location then pointed it at the temp directory I’d stored the files in previously. It figured it out and installed the ones I needed. What I found amusing is it then appeared under a category called “Atmel Devices” since I’d installed tools based on libdfu for these devices once upon a time ago. YMMV.

Once I had drivers installed I could then fire up PlatformIO in the VSCode editor and attempt to create a new project. I selected the board type “Maple Mini Original” and “Arduino” for the platform and let it do its business. Unfortunately the processor I have and the one on the original maple mini are different, so I had to change a few things in the platformio.ini file; my config is below. This config is based on a PlatformIO blog post written by Vortex314, can’t thank them enough for sharing this information (click).

platform = ststm32
board = maple_mini_origin
framework = arduino
board_build.mcu = stm32f103cbt6
board_build.f_cpu = 72000000L
build_flags = 
    -D USBD_VID=0x0483

So what is so special? Firstly there are separate board_build definitions to set the processor and speed for the board. Thankfully the cores between the original board and my Chinese clone are similar enough for this to work. Secondly there’s a heap of additional build flags that will build in a USB serial port. So if you’re used to the USB serial to debug your code this will still work. You can find out a little more about why this is necessary on Roger Clark’s website here (click).

It is interesting that the boot-loader contains only DFU code and that the application needs to have the USB serial built in separately. In the above configuration you may notice that the VID is 0x0483 which is by design, this means the Communications Device Class (CDC) will trigger the ST Serial drivers on a Windows installation if you have them installed. If you don’t you can find them here (click).

So from within the PlatformIO environment we can write our code and build for our target. Here’s my very simple test program that flashes the onboard LED (pin 33) and will send some test data to the USB serial port.

#include <Arduino.h>

void setup() 
  // put your setup code here, to run once:
  pinMode( 33, OUTPUT );

void loop() 
  static int i = 0;
  // put your main code here, to run repeatedly:
  digitalWrite( 33, HIGH );
  digitalWrite( 33, LOW );

  Serial.print("Test #");

So the last comment I need to make is in the programming of the device. When you hit the upload button from within PlatformIO you’ll see OpenOCD start and then pause with the comment “Searching for DFU device [LEAF:0003]” and if you wait long enough a subsequent message flashes by reading “Couldn’t find the DFU device: [LEAD:0003]” and nothing appears to happen.

Initially I thought my board was dead when it dawned on me… The Arduino uses a separate ATmega8U2 that is capable of resetting the target ATMega328 under software control, the STM32F103Cx is using the internal USB port and does not have this reset function (*face palm*). So when we start the program cycle we need to wait for the “Searching for DFU device” to appear and then manually reset our target to force the boot-loader into DFU mode momentarily where it is then caught and updated. Once done the process carries on as expected and you find you haven’t bricked your device.

Happy programming !

Small OLED Display on a rPi

Recently I was searching for a small graphic display that I could connect to a Raspberry Pi and fit within a Phoenix DIN enclosure I wanted to use.

There isn’t much space in the front of the enclosure I wanted to use, but a small 128×128 OLED colour display seemed it might fit.

Trawling through eBay I found what I thought to be a suitable unit and simply placed an order. There was very little information on the eBay site to tell me which display I had purchased so I just waited. When the display arrived it turned out to be a Waveshare SKU:14747 with the SED1351 controller.

A little searching around the web and I found an excellent tutorial written by the Freetronics Team for their 128×128 OLED display. It turns out our displays share the same SED1351 controller, so it was the logical place to start with my small display.

First task was to map the OLED pins to my rPi 3B+ 40-pin GPIO connector. On the rear of the display the pins and their desired function were clearly marked, so I mapped the pins like so;

OLED    | rPi      (pin)
+5      | 5V       (1)
GND     | 0V       (3)
MOSI    | SPI_MOSI (19)
SCK     | SPI_SCK  (23)
CS      | SPI_CE0  (24)
DC      | GPIO25   (22)
RST     | GPIO24   (18)

I have also included the rPi pin numbers I used, make sure you plug the display into the right pins if in doubt RTFM. Once it was wired I ran the following commands to make sure the rPi was absolutely up to date;

sudo apt-get update
sudo apt-get dist-upgrade
sudo reboot

The latest version of Raspbian Lite I was using (Buster) came with the fbtft frame buffer drivers already installed, so these steps were unnecessary. Since this Raspbian installation was fairly recent I decided that I didn’t need to update the rPi firmware using the rpi-update command like in other tutorials; YMMV.

I had already enabled the SPI bus on my Pi when I was coming to grips with the I2C bus. I found the tutorial at Sparkfun a really good reference and easy to follow. To create the frame buffer for the OLED device I ran the following command;

sudo modprove fbtft_device name=freetronicsoled128
dmesg | tail -20

Fingers crossed we see the following output in our terminal;

fbtft: module is from the staging directory, the quality is unknown, you have been warned.
fbtft_device: module is from the staging directory, the quality is unknown, you have been warned.
spidev spi0.0: spidev spi0.0 125000kHz 8 bits mode=0x00
spidev spi0.1: spidev spi0.1 125000kHz 8 bits mode=0x00
bcm2708_fb soc:fb: soc:fb id=-1 pdata? no
spidev spi0.0: Deleting spi0.0
fbtft_device: GPIOS used by 'freetronicsoled128':
fbtft_device: 'reset' = GPIO24
fbtft_device: 'dc' = GPIO25
spidev spi0.1: spidev spi0.1 125000kHz 8 bits mode=0x00
spi spi0.0: fb_ssd1351 spi0.0 20000kHz 8 bits mode=0x00
fb_ssd1351: module is from the staging directory, the quality is unknown, you have been warned.
graphics fb1: fb_ssd1351 frame buffer, 128x128, 32 KiB video memory, 4 KiB buffer memory, fps=20, spi0.0 at 20 MHz

The output here shows us that the SPI bus is OK and that we now have a frame buffer /dev/fb1 that is expecting to find a SED1351 LCD controller. So now it was time to display something so I used following command;

con2fbmap 1 1

And here is what I see;

w00t it works ! Now it’s time to go and find some graphics libraries that can talk to this frame buffer device… and to work out how to display text in boxes that is wider than 80 columns in WordPress…

MQTT Paho C Library

One of my upcoming “Radio” projects involves MQTT running on a raspberry Pi. I’m more familiar with C than I am with Python so to talk to the MQTT broker I went looking for a C based client.

I eventually settled on the Eclipse Paho MQTT C Client library, however it doesn’t come with an ARM based Linux binary package like you get for all the python peeps. Instead you’ve got to compile this from source, I guess since I’m intending to use C in the first place I should be OK. So back to the command line.

Starting with a bone stock installation of Raspbian Buster Lite I simply used the following commands in a shell;

$ sudo apt-get install git libssl-dev doxygen graphviz
$ cd /tmp
$ git clone
$ cd paho.mqtt.c/
$ make
$ make html 
$ sudo make install
$ cd /tmp
$ rm -rf paho.mqtt.c

I found all of the commands above in the git repository file. One thing I noticed was when compiling the libssl-dev library generated a good many “deprecated” warnings about old TLS ciphers being used (ie TLS 1.1, 1.2, 1.3 and SSL 2.0 & 3.0) so if you’re intending to use these it might be best to dig a little further. In my case this wasn’t important so I’ve filed it away here as a note to self for future reference.

So now it was just a question if the library works, the simplest way to do this was to compile the included examples and see if they work. So back off to the command line we go.

Marine Alternator Conversion

So while testing the heat exchanger and thermostat were working I also found the alternator was not charging the battery. I’d noticed that the volt meter on the dash was not showing more than 12V and then confirmed this with a multimeter across the battery. Sigh one thing always leads to another.

The original alternator has certainly been in the boat for a long while and was in a rather decrepit condition, someone had also taken to the upper arm of the alternator bracket with a grinder to make clearance, a sure sign it was not original.

So the alternator fitted to the Nereus turns out was a Delco 10SI chassis with an external RE55 bosch regulator. I’m quite familiar with this regulator since they were originally designed and made at my current work place here in Australia. This was certainly a long way from being a standard issue Ford alternator.

There are still replacements for these Bosch external alternators around, but they are now well and truly obsolete and getting pricey and hard to get. Even if I know who made them. The Delco alternator frame also could not be pulled apart, it was rusted solid. I tried for a couple of days with heat and Penetrene to get the frame screws that hold the two halves of the unit together to release. Alas they were firmly stuck and right on the verge of stripping, so there was certainly no point in sending it off to be rebuilt.

However one of the attractions of the Ford 250ci inline 6-cylinder engine is the ancillary parts are all based on the Ford 302/351W Windsor (hint: Ford engineers were clever or lazy !?!), so many of the V8 ski boat marine accessories from the 1970’s to mid 1990’s will fit my engine. So a bit of poking around the internet and auto parts stores resulted in me purchasing a Sierra 18-5957 marine alternator from a marine service agency in Queensland that has surplus stock on eBay. It was half the price of a new automotive alternator from a well known German Manufacturer and about the same price as the cheap Chinese knockoffs. Decision made.

Fitting the new marine alternator up when it arrived was a complete doddle (meaning easy), all that I required was a small spacer to pack out the foot on the lower bolt from 51 to 76mm. I had some old GM spacers that were 32mm long, I just cut one down to 25mm long.

Once I had it fitted up I had to pay attention to the clearance between the back of the alternator and the heat exchanger. By putting on a longer belt it meant I could hang the alternator further out from the block. So it was off to the auto parts store for a new belt which happened to be 40mm longer (11A1105) than the one I had already. There are even longer belts available and plenty of room on the control arm to move out further should I need it. I may however try to find a suitable arm to replace the one i have, it looks terrible due to its previous brush with an angle grinder.

Of note when replacing the alternator one has to be careful with the pulley diameters and make sure that the maximum shaft speed of the alternator is not exceeded. You’ve also got to compromise on the lower speed when at idle, otherwise the battery can still go flat. However reading the single small sheet of paper that the Sierra Alternator came with did not specify the maximum rpm. So oh boy I get to make some guesses.

The Sierra alternator came with a 50mm pulley and the standard crank pulley on a Ford 302 Windsor (including mercruisers) is 165mm, meaning at wide open throttle (WOT) the alternator would spin at 4800 x 165 / 50 = 15850 rpm. On my Ford 250ci inline- 6 WOT is 4500rpm and the crank pulley is 176mm, so 4500 * 176 / 50 = 15840 rpm; so roughly about the same.

I’m still not convinced that this is right and have emailed Sea Star Solutions who own Sierra to double check this is ok. There are alternator pulleys with diameters of 59.7mm , 66.7mm & 71.1mm. If these diameters look funny it’s because they are all technically imperial. However I’m more used to working in metric now days.

One benefit of the higher pulley ratio is some addtional output current at and around Idle. So reading the Sierra Alternator spec sheet the alternator at idle is rotating around 700 x 176 / 50 = 2464rpm, which should mean the alternator can deliver nearly 48A to a flat battery. This would make cranking on the anchor winch much less of a problem.

The Sierra 18-5957 alternator has an internal regulator, so all of the external regulator wiring could be removed. There were no wiring instructions in the box, but this is a common aftermarket alternator so there are plenty of instructions on the net.

So the trick with this alternator is to wire the red to a switched +12 wire from the ignition switch. The best place for this on a Ford 250ci is from the coil positive. Which on my moter is the opposide side to the alternator.

The black wire is the sense wire, it is not an earth. The sense wire means it is connected to the positive terminal on the battery. This means the internal regulator can measure the battery terminal voltage independantly of the +B terminal and allow constant current charging of the start battery to occur. It’s worth noting that if you are measuring the battery voltage of the console of your boat make sure it’s not from the ignition switch supply, which is wired to the +B pin of the alternator. Otherwise you’ll find the voltage being displayed abnormally high.

So once this was all done it was time to fire her up and give it a test. Nothing like making a video, hopefully these make sense.

Wooo that 3″ wet exchaust on a inline-6 with no muffer sounds good ! Now I can move onto checking the wiring and perhaps sea trials.