Yanmar 2gm20 issues (smoke and more)

[vas]

how do you define slow to start?
no reason I could think that exhaust elbow removal/refit affects starting.
I've played around a lot with my 2GM, managed to mess with the high pressure pump (thankfully only a tenner to get it checked dismantled and refitted from a local guy) had lots of issues with the lift pump which I finally removed altogether and fitted an electric one (was slowly leaking fuel back in the line), burnt the starter by continuous cranking, etc etc. Most of my "explorations" are documented here in PBO.

It's not happy to start from stone cold, full stop. Various tricks include (not mentioned in this thread yet) is to crank with closed accel for 20secs just to heat up things in there. Then 3/4full and crank to start. If compression is low, it may struggle and start on the one and then the second comes up... You can also try cranking with the one decomp lever up to help it speed up cranking. Check also battery, cables, ground from bat to engine, every little counts.
FWIW, injectors are fairly easy to remove then get them tested and refit. Few youtube videos on that.

V.

 

[OP30]

At this point "slow to start" is relative to past experience and imprecise. It used to start while holding the ignition for a couple seconds and if it didn't start right away I would stop and try again. Usually 1-3 tries was enough. Now I find myself having to hold the ignition for a concerning amount of time--10+ seconds--and its taking 5-6+ tries (I see you mention cranking for 20 seconds so maybe I'm being overly cautious). It starts easy only if I'm restarting immediately, leave it sitting for an hour and I have to start over.

I'll experiment with the different starting tricks you mention to see if it helps. The battery appears to be good and I've redone the cable runs recently and upsized the cables. I also have a lithium jump pack that I've a/b tested with and performance seems the same. The starter seems to work well as it is brand new, an upgraded part with proper bearings and a gear reduction (recommended by a specialist who I'm told is well regarded). The engine seems to run 30-60 seconds before any water comes out the exhaust. It sounds noticeably different without water flow, which raised concerns, and I can eventually hear the water building up in the system. I'll have to see if this behavior persists. Once it's going everything seems okay but I hold my breath...

I'm working on getting more acquainted with the injectors / pump and will figure out how to get a call back from the local tech.

Many thanks

 

[jwfrary]

In cold weather you could easily have to crank for 30 secs to get a gm to catch.

I have a feeling as vas suggeststhat one of your injectors isn’t quite right. Could have been rebuilt with inferior parts. Best checked and eliminated. While they are out a compression check would be wise, you can get these fairly cheaply on eBay, and you will have to customise an adaptor to fit the yanmar chamber.

if your lucky you might have a yanmar service agent near your with an Adaptor already made up.

I ask about the alt due to potential for overloading but sounds like your managing that already.

as vas says lift pumps can be a pain on these and if they fail they can leak fuel into the the crank case so something to watch for. They can be had fairly inexpensively now so could be worth changing out for reliability.

When you re installed the injectors you will need new gaskets for the precombustion chamber and injector seals. It wouldn’t be a bad idea to clean the pre combustion chamber, anyway and might afford you a peek in the cylinder with a camara.

 

[vas]

OP30,

seems to me that most GM owners would be happy to have your engine
by all means try to improve, I wouldn't expect much though.
my two main engines are 6.7lt straight 6 turbodiesels (non-common rail), you just look at the bloody start button and they start on a split second (also no glow plugs!)
This small thing is v.different.

cheers

V.

 

[dukeofted]

If you turn over the engine with a socket on the crank pulley you will be able to get a rough idea on the compression. It should be really quite hard to turn it past the compression point if your compression is decent. You can compare the force for each compression to compare cylinders. Could be worth taking the cylinder head off and seeing the state of the valves and seats. A lap in of the valves if there is a bit of rust will help a lot.

 

[OP30]

Thanks again for all the help!

Update: I had the local Yanmar guy out and he says I don't have an engine problem I have a fuel problem. Mainly water. The secondary fuel filter was not full of water but had enough that he thought it was causing issues. We replaced that filter and I'm working on a plan to try to clean the fuel tank more thoroughly.

I have been slowed a bit in working through all of your suggestions because I killed my start battery turning the thing over (starting and bleeding the injector lines). With how much I have to spin the engine to get it started when it has sat for a while the mechanic thinks I may be losing fuel prime somehow. He didn't know if there is a check valve somewhere in the system but generally this wasn't his biggest concern.

Do any of you have thoughts on this? Where would you look if you thought fuel was draining back into the tank? I haven't had this issue in the past, could it be a check valve that isn't closing, or maybe the riser pump was damaged from the water? The fuel line does have a ball pump also.

Thanks

 

[vas]

the idiotic engine mounted fuel filter most likely, the two bleed screws on top, stripped threads, missing/wrong washer/oring whatnot. Took me ages to sort it (and still not 100% fine).

 

[Jesgatt]

Hi, I have a similar problem. My boat is a Dehler 36db with a Yanmar 2GM20 raw water. The engine used to run smooth and rev up to 2700 easily on load, however lately it is arriving up to 2500rpm (at max throttle on load), and black water and smoke is coming out of the exhaust. Tests conducted till today:

1. Engine starts immediately.
2. Conducted a compression test (by my mechanic) and the result gave around 400psi per cylinder.
3. Taken injectors for a service and injector nozzles have been changed.
4. Inspected stainless steel exhaust elbow and found out to be ok.
5. Tested engine off load and managed to rev it up to 3400rpm.
6. Inspected water locks and found to be ok.

Can someone please guide me on how to proceed?

Thanks

 

[black mercury]

It could simply be a fouled propeller, have you checked it for fouling?
Are you testing it under way or tied to a pontoon? An engine will struggle to reach same rpm under load when boat is tied to a pontoon compared to when in open water.

 

[Jesgatt]

It could simply be a fouled propeller, have you checked it for fouling?
Are you testing it under way or tied to a pontoon? An engine will struggle to reach same rpm under load when boat is tied to a pontoon compared to when in open water.

Update:
I am testing the boat both tied to the pontoon and under way and still getting issues: The maximum RPM under load is 2400rpm. In the mean time I did the following:
1. Changed the exhaust pipe (from elbow to the water lock and to the output elbow)
2. Cleaned Prop and hull from any fouling
3. Cleaned fuel tank and replaced all fuel in the tank
4. Replaced water separator and fuel filter
5. Performed another compression test - results OK
6. Checked clearance of valves (according to manual)
7. Checked timing of engine

Note: I noticed a fuel leak in the copper high pressure pipe between the injectors. I ordered it from the supplier and I am waiting for it to arrive. Will keep you updated.

Thanks

 

[Jesgatt]

This only happens when on load; off load I manage to get 3400rpm with no issues at all.

 

[IanCC]

how do you define slow to start?
no reason I could think that exhaust elbow removal/refit affects starting.
I've played around a lot with my 2GM, managed to mess with the high pressure pump (thankfully only a tenner to get it checked dismantled and refitted from a local guy) had lots of issues with the lift pump which I finally removed altogether and fitted an electric one (was slowly leaking fuel back in the line), burnt the starter by continuous cranking, etc etc. Most of my "explorations" are documented here in PBO.

It's not happy to start from stone cold, full stop. Various tricks include (not mentioned in this thread yet) is to crank with closed accel for 20secs just to heat up things in there. Then 3/4full and crank to start. If compression is low, it may struggle and start on the one and then the second comes up... You can also try cranking with the one decomp lever up to help it speed up cranking. Check also battery, cables, ground from bat to engine, every little counts.
FWIW, injectors are fairly easy to remove then get them tested and refit. Few youtube videos on that.

V.

There is both a yanmar marine engines owners group and a 2gm20 group on Facebook. Both super helpful.

 

[ghostlymoron]

same issue.....in the end replaced it with a 20hp BETA and never looked back

You could probAbly have replaced it with any new engine and got the same result. Not knocking Betas by the way.

 

[black mercury]

I would make sure the precombustion chambers are clean from carbon and not burnt or worn, you need to remove injectors for this. Your symptoms do suggest that the engine is getting more fuel than it can efficiently burn, either the air intake is restricted or exhaust restricted. There was one yanmar many years ago that would smoke and it turned out there was water (a small amount) that was entering the cylinders and obviously affecting the combustion. I discovered that by shutting the water intake, removing the impeller and running the engine momentarily with no water running through it (it was raw water cooled). It ran well with no smoke, only ran it for seconds.

 

[UK-WOOZY]

following, i have a 1988 raw water engine. Replaced the water pump, whole fuel filter, hoses, drive plate, exhaust elbow and starter motor for new since getting the boat in 2017. The engine has always had a strange jingly metallic noise near the back of the engine which i have no idea is but seems to run ok. "touch wood"

 

[Jesgatt]

Problem solved - Propeller was fouled. I got a diver to clean and voila - back as new