Yanmar 1gm10 stalls in gear, prop shaft friction or fuel supply?

[ApexTheGunn]

I'm pretty new to diesel engines and have only had my small leisure 23 a year, so looking for some input from more experienced boat owners.

Earlier in the season I had starting issues, and suspected a range of fuel supply issues that might be causing it, from old rusty tank to old filters and leaking bleed screws. I have now replaced tank, all hoses, the whole fuel filter assembly, checked all bolts and jubilee clips and bled and rebled the engine. I seem to get decent flow out the bleed points with the manual lift pump.

The engine starts well after 20 seconds or so of cranking now, and runs fine in neutral up to high revs, exhaust looking clear and no discernible leaks or weird sounds. However, as soon as I engage reverse or forward gears the prop will spin slowly but the engine will start slowing until it eventually dies.
If I keep engaging reverse gear after maybe 5 mins of engaging and disengaging, barely keeping the engine running, eventually the prop will spin up and I'll be able to rev and create propulsion in reverse. However forward will still stall the engine (different gearing ratio?). After another 5 mins of engaging forward (and helps with forward momentum of the boat) forward will run fine as well. If the boat sits for a few hours it'll be back to scratch for the whole process.

Turning the prop shaft by hand there is noticeable resistance, but I can just about turn it by hand using full force from inside the engine room (holding on the the prop shaft itself). Testing this on other boats there is significantly less resistance.

I know the 1gm10 torque is around 16Nm, but have no practical experience of how strong this engine should be, and how much resistance is too much, and haven't measured the resistance in the prop shaft yet.

As I've also read about many gm10s with similar symptoms in gear being due to fuel supply, or a worn lift pump I'm considering bypassing or replacing the pump as well, but also have no frame of reference for how much fuel flow is normal.

If it is the prop shaft resistance I have no idea how to resolve it, is that a big job of replacing cutlass bearings or whole prop shaft?

Has anyone come across this before and have insight into if either of these two things are reasonable causes of these issues?

 

[Daverw]

Have you thought of splitting the shaft coupling and running without prop load? This will eliminate the gear box and also the shaft should then turn very freely

 

[Graham376]

You should be able to turn the shaft with only a little resistance, what type of stern gland do you have? If a stuffing box, sounds like it needs backing off a bit. Have yo checked the prop is not fouled, clear of ropes, plastic bag etc?

 

[scottie]

Is it possible that alternator is over loading engine at low revs
Seem to remember this happening on one

 

[jwilson]

Shouldn't be that difficult to turn the propshaft by hand. If the boat is in the water might there be a lot of old rope/weed/nets stopping the prop from turning freely? Or old nylon fishing line pulled into the cutless bearing and making it tight. A 1GM10 is not a particularly powerful engine at about 9hp, but many years ago I had a boat of about 8 tons with an ancient 7 hp, which at the time I thought was quite adequate power.

 

[Refueler]

First thing :

You say takes 20 seconds cranking and then she fires .....

That sounds like she's fuel starved and cranking is drawing up fuel to get her going.

Such an engine will need minute fuel to rev without load ... but put into gear and suddenly that minute fuel flow is not enough ... she will slow or stall.

Repeated in / out of gear sounds like you are making the engine exert short bursts to draw fuel sufficient to drive....

Sounds to me as if you have poor fuel feed ....

 

[Channel Sailor]

As a long time 2gm20 owner, I would say 20 seconds is a long time, too long, to start a Yanmar. 20 seconds “or so” I would say indicates something is very wrong there anyway. How about blocked manifold, low compression (but you say no smoke so maybe not), fuel problem of some kind, maybe with air getting in when at rest, filters clogged up, just guessing.

When out of gear (and engine off of course) a hand on the propshaft should be able to turn it fairly easily. A hand on the clamp that is on the end of the propshaft should be easy to turn to turn the shaft. stuffing box problem or prop fouled I suggest.

 

[PCUK]

Have you checked that the propeller isn't fouled? I mean properly checked by lifting the boat or getting underneath?

 

[Refueler]

I know of a 1GM that takes 20 seconds or more to start - but she's bad on compression ... once started she seems to 'tighten up' and run ok ...

I don't think we have that here - at least I hope not.

My finger is itching to point at fuel starvation ...

Just a comment .... be careful turning shaft by hand ... accidents have occurred where diesel engine has fired and kicked ... (even gasoline engine if fitted with CDi ... I have a scar from that !!)

 

[ApexTheGunn]

Thanks for all the input, this has given me some things to consider and some new angles I hadn't thought of. It's good to know that it shouldn't be so hard to turn the prop shaft - I'll dry out the boat this weekend on the slip and check properly underneath as well as the stern gland (which I think is a stuffing box) as it isn't unlikely that it is on pretty tight (never had a drop of water come through), and I'll also try to eliminate anything with the gear box. The boat has been in the water all winter so some growth is definitely there so will give it a good clean.

I suspected the 20 second crank time indicated it is still a little fuel starved but couldn't think of other things to change given I have replaced almost everything. But I'm realising bypassing the original lift pump would be a cheap and easy thing to try, and can't hurt. After seeing other people here on the forums replace the pump with e.g. a Facet electric pump, I think that would be a nice upgrade and remove an additional variable from the equation.
I'm really hoping it isn't the compression pressure, but if nothing else fixes it that will be the logical next thing to look at I think.

I'll report back if I make any progress this weekend, cheers for all the comments!

 

[Refueler]

If you have a stuffing box gland ... I suggest you back of the 'nut' and let the packing ease up .... let the water leak in ... and then slowly take up till water is a drip every 30 sec's or so .. this then proves the packing is being lubricated by the water ....
To stop the drip when boat not used - that's when I use the greaser .... when moored - give greaser a couple of turns .... and before starting a trip - I give it a couple of turns.

If you have run the engine with that tight packing for last season or so - then its likely scorched - which creates a hard surface to the packing. It then needs replacing.

 

[rotrax]

Is it possible that alternator is over loading engine at low revs
Seem to remember this happening on one

This is a definite possibility.

Disconnect the drive belt for a few seconds-just long enough to see if it is OK without a highly magnetised alternator.

If it is, investigate the 'soft start' function. Our Yanmar 4JH4-HTE has it.

 

[Channel Sailor]

Re the lift pump concern. Is there any way the fuel tank can be lifted temporarily to be located higher than the injector. This means the injector pump has nothing to do. Also small/tiny fuel leaks might show up over a few days.

 

[ApexTheGunn]

The adventure continues. This weekend I was able to dry out the boat and clean the hull and check prop etc, as well as run the engine more to see how it behaved.

There was a lot of growth (see pic!) on the prop shaft after a year in the water, and after cleaning that off there was less stalling in gear, and the boat ran a little better, however it still took time for the engine to warm up, but after 5 minutes I was able to motor around just fine, however I am noticing a significant delay in response to increasing the throttle.

There is still a lot of resistance in the prop shaft so I will also loosen the stern gland to see if that helps. I have attached a picture of the stern gland, I couldn't find clear references online of similar ones so was hesitant to remove the rubber sleeve as I didn't want to start flooding the boat. Does anyone recognise if this is a normal stuffing box and the adjusting nuts are just under the rubber sleeve?

The startup issues are worse than I remembered. It takes several 20 second intervals of cranking until I get the engine to fire, and it only does so hesitantly for a few times until it properly starts.
I bypassed the lift pump completely with an electric pump and have a clean tank with new hoses and fuel and new filters pumping fuel at a high flow rate to the high pressure pump with no noticeable leaking or air bubbles. I also get what looks like good flow at the injector pipe if I undo that at the injector and manually crank the engine with the decompression lever lifted. I also get a continuous dribble of fuel out the return hose when the engine is running (which I'm running to a bucket at the moment) which I would think means there is enough fuel reaching the injector(?)

I haven't checked the exhaust elbow/manifold yet which is next to try. When I rev in gear it looks quite different from other boats I've sailed as water is shot out the exhaust at some pressure almost atomising the water droplets, and it leaves sooty residue floating on the water. Not sure if partially blocked it could lead to startup issues like these. (I made a gif of exhaust, probably hard to tell though: https://tinyurl.com/4sx5n62v)

I'm not noticing any smoky exhaust, nor oil consumption in the engine, and there is significant resistance when hand cranking through the compression phase, so I'll hope compression is ok and leave that until last.

I'm wondering if checking/replacing the injector is worth trying - although others have said it is very rare and unlikely to be the injector. I'll also try disconnecting the alternator as was suggested.

If anyone has additional ideas of what could be going on I'd gladly take advice, in the meantime I'll keep trying things.

 

[scottie]

I presume that the propeller photo is before cleaning and would contribute to shaft drag problems
The stern gland is what I would call a Scandinavian style and is a mid section with possibly bearing (white metal) with lip seals at either end and greased via the pipe teed off apart from cleaning and or replacing the seal it is maintenance free apart from checking a free flow of grease in .the tube water pump grease should not be used ly


The neck hose is a specific type of rubber to resist the grease and must not be reinforced with wire
With the flexibility built into the coupling non flexible mounting’s would not normally be used

 

[ApexTheGunn]

I've finally been able to resolve all the starting and running issues and long story short: bad compression fixed by reseating valves and injector.

Now the engine runs much better than it ever has, starts up after a couple turns and has no problem driving the prop-shaft despite the same resistance (except the cleaning up). It's been good to get a better feel for how strong the engine is when it operates as it should, no problem driving in gear at high revs now.

This being my first engine I thought the resistance I felt when hand cranking was good, but in retrospect it was very soft and spongy. The difference now is night and day, it is very hard now to turn around by hand through the compression phase.

What I did to fix it:
As I took the engine apart this weekend I checked exhaust and injector spray patterns and both looked reasonably good, however the cylinder head, valves and piston had a lot of gunk and pitting and the valves looked very poorly seated (see pics). The injector clamp also seemed a bit loose.

Cylinder head and exhaust valve before:


So I cleaned it all up as good as I could and used lapping paste and a battery drill to grind the exhaust valve and seat to close better. This took a few hours of grinding, and I couldn't get it perfect, but improved it a lot:


There is still some pitting and the condition of the cylinder head and piston are not great, but replacing those would be a much bigger more expensive job, so decided to try just the best I could with the current parts. Putting it all together I replaced all the gaskets, cleaned up exhaust ports, exhaust manifold and the cooling passages and hoses. Then I tightened down the head cylinder bolts some of which were a bit loose, readjusted the valve rocker, made sure the injector was seated well and tidied things up.

And despite it being quite a simple fix with some pitting and wear remaining the difference is night and day, it massively improved compression, the engine starts on idle, sounds better (more crisp, less spongy) and drives the prop easily.

I was very hesitant to address potential compression issues since I assumed it meant taking the engine out the boat, replacing piston and more, but I was able to do all this with the engine in the boat over the course of 2 days, with the help of several excellent YouTube videos, and about £100 worth of new gaskets, a torque wrench and some lapping paste.

 

[bikedaft]

Well done! Enjoy the boat

 

[vyv_cox]

The stern gland appears to be leaking quite badly. As has been said, these contain lip seals as used in automotive applications, very cheap to replace. Best done now before they fail in a more catastrophic manner.

 

[BB1]

I'm pretty new to diesel engines and have only had my small leisure 23 a year, so looking for some input from more experienced boat owners.

Earlier in the season I had starting issues, and suspected a range of fuel supply issues that might be causing it, from old rusty tank to old filters and leaking bleed screws. I have now replaced tank, all hoses, the whole fuel filter assembly, checked all bolts and jubilee clips and bled and rebled the engine. I seem to get decent flow out the bleed points with the manual lift pump.

The engine starts well after 20 seconds or so of cranking now, and runs fine in neutral up to high revs, exhaust looking clear and no discernible leaks or weird sounds. However, as soon as I engage reverse or forward gears the prop will spin slowly but the engine will start slowing until it eventually dies.
If I keep engaging reverse gear after maybe 5 mins of engaging and disengaging, barely keeping the engine running, eventually the prop will spin up and I'll be able to rev and create propulsion in reverse. However forward will still stall the engine (different gearing ratio?). After another 5 mins of engaging forward (and helps with forward momentum of the boat) forward will run fine as well. If the boat sits for a few hours it'll be back to scratch for the whole process.

Turning the prop shaft by hand there is noticeable resistance, but I can just about turn it by hand using full force from inside the engine room (holding on the the prop shaft itself). Testing this on other boats there is significantly less resistance.

I know the 1gm10 torque is around 16Nm, but have no practical experience of how strong this engine should be, and how much resistance is too much, and haven't measured the resistance in the prop shaft yet.

As I've also read about many gm10s with similar symptoms in gear being due to fuel supply, or a worn lift pump I'm considering bypassing or replacing the pump as well, but also have no frame of reference for how much fuel flow is normal.

If it is the prop shaft resistance I have no idea how to resolve it, is that a big job of replacing cutlass bearings or whole prop shaft?

Has anyone come across this before and have insight into if either of these two things are reasonable causes of these issue