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post #1 of 4 Old 04-03-2011 Thread Starter
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3GM yanmar hard starting

I am helping a friend with his 92 era 3gm in a 1992 35.5 hunter. I have had a similar engine in a 1991 37.5. My 37.5 3gm always started very quickly, hardly turning over on starter before firing up on all 3cylinders. My buddies engine started the same untill about two years ago when at times when stated after sitting for a day or two, it required a lot of cranking and eventually started running, roughly for 30seconds or so with a fair amount of black smoke. We have been trying different things to solve this startin problem the things that have been done are:
mixing elbow change, clean fuel filters , new injectors, injector pump rebuild, new hight pressure steel lines from injector pump to injectors, compression check ( within limits) we now notice fuel weep from the area of the injectors where the high pressure steel lins is attached, found by using paper towel blotting after running engine for 15 mins or so. we are fairly sure that this may be the cause of this agravating problem We are wondering how tight should this compression coupling be torgued down? And has anyone had this type of problem and actually solved it?
The engine still behaves the same hard stating after sitting for a day , but runs fine when warmed up. Starts fine unless it sites for a day. I did find a post from a fellow who had the same experience in 2008 but solution to the problem was never posted on this forum.
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post #2 of 4 Old 04-03-2011
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hard starting 3gm after few days

I had a similar problem with long cranking after the boat had sat for a few days. My problem ended up being a slight air leak in the secondary filter bleed screw. The washer (assuming it is the copper one) needs to be replaced each time you bleed it. I ended up going to a nylon washer. Problem (at least for me) solved.

Also find that putting the gear in neutral and moving the throttle to give it more fuel also helped getting it to start.


Ed Reiss
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post #3 of 4 Old 04-04-2011
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Fuel leak will do that, and like ereiss said, that bleed screw washer can be the problem. Just don't do what my PO did and crank that screw down harder--you'll just strip out the threads in the aluminum filter housing. Since you just replaced the high pressure lines and injectors and now see a weep there, I wouldn't think that was your original cause.

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post #4 of 4 Old 04-07-2011
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After sitting my 3gm30f does the same. I flip the decompression levers on, put it in neutral, give it almost full throttle and crank it for 3-4 sec. Then turn off the decompression levers, return throttle to slow turn on the cooling water intake and crank to start. Usually starts right up, If I just try to start it without doing this first it won’t.
I would also replace your copper crush washers.

That derelict boat was another dream for somebody else, don't let it be your nightmare and a waste of your life.
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