Dicky tickover

[longjohnsadler]

Recently bought a Sadler 32 with a Yanmar 2GM20, dated 1990. Set out last Saturday from Lough Swilly (Donegal) to go round Malin Head to haul out in Coleraine. Has to be done at some pace to stay in tidal window. Extract from log something like:
0730 Leave pontoon at Fahan. Wind F2, following. Under engine. Frank Sinatra on CD
0930 Nearly at top of L.Swilly. Wind increases F3/4. Kill engine. Start sailing
0945 Wind drops again. Drop sails. Start engine.
0946 Engine falters, no power, black sooty deposit from exhaust (not oily) covers water behind. Kill engine. Kill Frank Sinatra. Discretion etc etc, turn back for Fahan.
1000 Now beating against wind and tide. Perhaps the engine has had time to reconsider...
1001 Start engine. It has! More or less normal, no black deposit. Motor home. reinstate Frank (limited CD collection)
1300 Back at Fahan, tide too low to enter marina. Pick up mooring. Stop engine.
1305 Friendly local suggests next mooring along a better bet. Slip mooring, start engine and....no power, black sooty deposit (see earlier). Struggle back onto mooring.

Next day.
1100. Start engine to motor 200 yards back into marina. After initial puff of sooty stuff, engine seems ok. Return to pontoon.

If anyone has any ideas where to start looking, I'd be most grateful. Engine oil appears to be same as when I set out.

 

[mtb]

Blockage would be my favorite .
cheers
Mick

http://homepage.ntlworld.com/boats
I want a big steel ex trawler or tug cheap needing work

 

[toad]

Check the engine stop lever is returning fully to the run position after you have stopped the engine.

 

[jfkal]

Got a Yanmar 3GM30 with similar symptoms. Figure it is one of the following:

Old age loss of compression
Critters on the prop --> overload
High power alternator drags down the RPM until it stalls

Mine does not start on idle. Need to throttle up the 2/3 and reduce to 1/3 after it fires, run for a while until it accepts idle so I can get into gear. A bit annoying but I got used to it. Serviced injectors, valves, injection pump all to no avail. Adjusting the fuel delimiter yields even more smoke and soot only.
Glad for any better suggestions as well.

 

[ccscott49]

It sounds as if the excess fuel button, if you have one, is sticking or the rack in the injector pump is sticking in full fuel position, giving you excess fuel, which is generating the black soot/smoke, something like that anyway!

 

[longjohnsadler]

Yeah, mine will only start on high throttle too unless still warm.
Initial thought on first occurrence was fouled prop, but shouldnt happen twiceand clear itself. Interested to see servicing injectors and pump made no difference as this was suggested to me.
A Yanmar dealer on S. coast said double fouling unlikely, but if one side of the folding prop wasnt unfolding (can this really happen?) the whole thing would be unbalanced and produce this effect.
The sooty deposit is definitely black and solid tending to make me think it isnt unburnt fuel, but I'm no expert. Another suggestion has been some carbony build up in exhaust box or pipes which reaches a critical point. Maybe I'll look in here first.
Thanks all for suggestions, but if you've any more.....

 

[jleaworthy]

Your symptons suggest lack of air. Suggest you check air flter first and then your exhaust which might have been overheated in the past and then collapsed internally. The fact that your engine ran OK for some time points to the latter.

If neither is a problem I would suspect air in the fuel supply. Strangely enough air in the governor can give temporary overfueling with its black smoke etc. Remedy is the usual bleeding/checking routine. Good luck.

 

[dickh]

Had a similar problem on a Perkins Perama last year, after having the injectors serviced and injector pump overhauled, it turned out to be a carboned up exhaust elbow - only a contorted 5/16" Dia. hole thro' the centre. Would have saved myself £200 if I had checked this first.
Suggest you check out this carboned up elbow/exhaust box first, being the cheapest option, then collapsed exhaust hoses, then air in fuel, then blocked fuel filters,(perhaps adding Soltron to fuel??) then injectors, then injector pump.
Good luck, keep us informed of the outcome.


dickh
I'd rather be sailing...

 

[SimonD]

Yes, yes, yes! I had the same symptoms recently. Turned out to be the stop lever not going fully back. Ashamed to say it was my fault - I'd fiddled with the cable the day before. (If it ain't broke, don't fix it!)

 

[jfkal]

Doubt is long term carbon built up. That would stick and not move easily. If the fuel burns not evenly or completely only the hydrogen oxidises but not the carbon which creates that fine carbon stuff which floats on the water (ideal material to start to make diamonds). I suspect bad compression at least in my case since I can conform some blow by. Seems then worse on startup since hight throttle lots of fuel bad compression until the oil gets going and the engine warms up. Check for blow by by taking off the oil cap and see whether you get exhaust fumes there.