Lister Petter AC2W Cutting out when hot

[Altonx]

Hi all
My AC2W has an issue where it cuts out when hot, idles fine when cold, it starts ok, had some white smoke from the exhaust under load and noticed drips of seawater coming out between the barrel and cylinder head.
The top end of the engine is now stripped, heads are having a light skim but look in decent condition, obvs new head gaskets being fitted and i will be adjusting the bump clearance as req (on removal of the heads i checked bump clearance i was measuring 0.035, tolerance is 0.022-0,026)
Do you think the cutting out issue could be a separate issue?
I am seeing a few posts online with the same issue but none come up with an answer, they all seem to suggest fuel pump issue, could pump timing cause that?

 

[Boater Sam]

It won't be timing.
You mean it refuses to idle when hot?
Usually its fuel problems but check that the linkage is not responsible, things expand when hot.

 

[Altonx]

It won't be timing.
You mean it refuses to idle when hot?
Usually its fuel problems but check that the linkage is not responsible, things expand when hot.

Thanks Boater Sam
Good to know I havnt got to mess about with the spill point.
I won't say it refuses to idle but it doesn't like to idle when hot, after say an hours run in my boat when coming back to its berth and I slow down to manoeuvre into my tight berth it always cuts out which is definitely not needed, only way around d it is to keep the rpm up which doesn't help manoeuvring, after I restart it idles sometimes.
What linkage are you referring too, guvenor linkage?

 

[vyv_cox]

A very long time ago I owned a boat with a single cylinder Yanmar (YS?) that had exactly the same symptoms. Some investigation revealed that the coolant passages in the cylinder head were blocked with salt crystals. They were straight, easily cleaned out with a drill, which fixed the problem.

 

[Altonx]

A very long time ago I owned a boat with a single cylinder Yanmar (YS?) that had exactly the same symptoms. Some investigation revealed that the coolant passages in the cylinder head were blocked with salt crystals. They were straight, easily cleaned out with a drill, which fixed the problem.

Wow thank you.
As it happens I have the barrells stripped off the engine now and whilst tinkering I removed the anodes from the barrells, one of them had completely disintegrated and the other was half missing with clumps of used zinc in both barrels, I have new anodes coming in the post and have also blown out all the pieces inside the barrells with compressed air so fingers crossed it was a blockage causing overheating issue that has hopefully been now sorted, all will be revealed in a few weeks when its back up and running

 

[Poecheng]

Are the valve seats clean and valves correctly adjusted. Had similar on Honda single cylinder m/c and one of the valves was opening (ie not sealing) in the heat but, when stopped and a little cooler, it would start again. A good clean and re-grind and it went away. I am sure this has all been checked as you have the head off anyway.

 

[Altonx]

Are the valve seats clean and valves correctly adjusted. Had similar on Honda single cylinder m/c and one of the valves was opening (ie not sealing) in the heat but, when stopped and a little cooler, it would start again. A good clean and re-grind and it went away. I am sure this has all been checked as you have the head off anyway.

Valve clearances will be set correctly when I rebuild the engine, the inlet gap did appear to bee quite large on removal but I didn't measure it.
Thanks Poecheng

 

[[194224]]

I''m going back some years now when I had an AC2W and in the middle of the channel (in fog of course!) it cut out. I didn't have an over temperature sensor fitted so all I had was the engine stopping. On dismantling the engine I discovered two things The bumping clearance was too big. Petter had increased the thickness of the head gasket as the earlier thin ones were prone to blowing. On fitting the new thicker ones the advice was to skim the head or cylinder to to correct the bumping distance (and consequently the compression). I chose to lift the two pots off and remove a shim from the bottom. Luckily that brought the bumping clearance into range. Many owners just took the easy route and fitted the new gasket and didn't bother with the skimming, that's what had happened to mine. Yours may be the same but I doubt that has anything to do with the engine stopping when hot.

I suspected my engine had overheated. When we got to Cherbourg it started fine but I was reluctant to run it for long. There was a metal coolant pipe running between the two cylinder heads. I removed this and found it to be badly blocked. I sawed off most of the pipe, cleaned up the two residual spigots, refitted them and fitted a thick reinforced hose between the two.

 

[Altonx]

I''m going back some years now when I had an AC2W and in the middle of the channel (in fog of course!) it cut out. I didn't have an over temperature sensor fitted so all I had was the engine stopping. On dismantling the engine I discovered two things The bumping clearance was too big. Petter had increased the thickness of the head gasket as the earlier thin ones were prone to blowing. On fitting the new thicker ones the advice was to skim the head or cylinder to to correct the bumping distance (and consequently the compression). I chose to lift the two pots off and remove a shim from the bottom. Luckily that brought the bumping clearance into range. Many owners just took the easy route and fitted the new gasket and didn't bother with the skimming, that's what had happened to mine. Yours may be the same but I doubt that has anything to do with the engine stopping when hot.

I suspected my engine had overheated. When we got to Cherbourg it started fine but I was reluctant to run it for long. There was a metal coolant pipe running between the two cylinder heads. I removed this and found it to be badly blocked. I sawed off most of the pipe, cleaned up the two residual spigots, refitted them and fitted a thick reinforced hose between the two.

Thanks for the interesting info,
I'm aware of the larger gaskets that were used, as I said I did measure the bump clearance and it was bigger than it should be, also the Anodes were broken up in the heads (maybe restricting water flow) i will check the coolant hoses between the heads as well. Thank you.

 

[kieron riley]

Petter mini twins are very prone to corrosion in the cylinder heads , due to them being aluminium , hence the anodes . It is extremely important to keep changing the anodes ( when the show signs of excessive corrosion( sounds like yours where well overdue) so do have a really good check of the cylinder heads for signs of corrosion, particularly around the valve seats , I have seen corrosion on heads that looks superficial , but I’m afraid there is actually no such thing as superficial on a petter head . It could well have small leak on one or even both heads leading to a slight compression leak , and when the engine is running fast it will hold its compression but when slow running even a slight compression loss could cause the engine to cut out. I do have quite a few spares for these engines so if you need , then ide be more than happy to help if I can. Kieron

 

[Altonx]

Petter mini twins are very prone to corrosion in the cylinder heads , due to them being aluminium , hence the anodes . It is extremely important to keep changing the anodes ( when the show signs of excessive corrosion( sounds like yours where well overdue) so do have a really good check of the cylinder heads for signs of corrosion, particularly around the valve seats , I have seen corrosion on heads that looks superficial , but I’m afraid there is actually no such thing as superficial on a petter head . It could well have small leak on one or even both heads leading to a slight compression leak , and when the engine is running fast it will hold its compression but when slow running even a slight compression loss could cause the engine to cut out. I do have quite a few spares for these engines so if you need , then ide be more than happy to help if I can. Kieron

Thank you Kieron
Great info
Heads are off and corrosion was surprisingly not bad at all, I was expecting severe wear around water jackets but they are fine, heads have had a skim, 0.25 mm off one and 0.30mm off the other, I have noticed both inlet valves are not 100% sealing, very slight amounts of brake cleaner ive used to clean the heads off is seeping through the inlet valves so I will lap them in, I have 2 new anodes coming in the post at a ridiculous price of £6.15 each as opposed to the £60 each fleabay cost.
I'm hoping the failed head gaskets and the larger than spec bump clearance and large tappet clearance were responsible for the issue but until it is rebuilt I won't know, im waiting for 1 more head gasket set to arrive in the post and hopefully within the next couple of weekends I'll have it running again.
Great to know you have plenty of spare parts, they sure are hard to come by.
This engine rebuild sourcing of parts has literally taken over my life the last couple of weeks haha

 

[kieron riley]

Sorry but should have mentioned , you may need the valve seats recut to match the now slimmer head , it’s just possible that the valves may now fit in proud of the head , causing damage to both valves and pistons, I’m not sure if I have the measurements at home( I’m in Cyprus at present ) back on Sunday, so I will have a look for you

 

[Altonx]

Sorry but should have mentioned , you may need the valve seats recut to match the now slimmer head , it’s just possible that the valves may now fit in proud of the head , causing damage to both valves and pistons, I’m not sure if I have the measurements at home( I’m in Cyprus at present ) back on Sunday, so I will have a look for you

Thanks Kieron
I did check the measurements in the manual, I think the clearance between valve and piston is something like 1.3 to 1.9mm, obviously I have no idea how many times the head has had a skim so I will check on rebuild, but pleasing to know there is a decent gap also bearing in mind that the valves are never fully open when the piston is at tdc

 

[Altonx]

Quick update, i rebuilt the engine this morning, bump clearances spot on, valve clearances spot on, I stripped heads replacing valve stem oil seals and gave the valve a good lapping in (not done that in a while), so far so good, had the engine running for a good 40mins, no nasty surprises, couple of weeping water hoses that needed a quick tighten but so far so good, engine idles well and revs well also appears to be a bit more responsive, sounds better as well, run out of time today so didn't get chance to take the boat out for a spin, that will be the telling time! Will have to wait a fortnight for that.
I would love to set the min and max rpm up but without a tachometer its near on impossible to set it correctly other than by ear, Ive bought a digital rpm reader but doesn't seem to be very accurate.
Cant seem to upload an mp4 compressed video of the engine running?

 

[kieron riley]

Congratulations ,hope it gives you the long service mine has given me. another improvement you could do is to make it indirect cooling ,add another water pump and a heat exchanger. Cuts the need for regular new anodes and reduces likelihood of corrosion

 

[Altonx]

Congratulations ,hope it gives you the long service mine has given me. another improvement you could do is to make it indirect cooling ,add another water pump and a heat exchanger. Cuts the need for regular new anodes and reduces likelihood of corrosion

Thank you
Interesting idea but having found a source of Anodes at £6 each I think it would be cheaper to stay as I am (im guessing I'll get longer than 12months from each anode?), the boat is only in the water for 6 months of the year and used probably on average once a fortnight with trips no further than 6 miles at a time, every trip ends in a good fresh water flush as well, However if I do ever replace the engine for something a bit more powerful I will definitely be looking at a heat exchanged engine