won't turn over - cylinder 3 full of gas

1989 Pro 50. At the lake this weekend and had this problem. The only time I've seen it do something like this is before I removed the oil injection system. It actually had cylinder #3 completely full of 2 stroke oil. I didn't know this had happened and tried turning it over. Now I think that's why #3 is 5 lbs lower than all the rest on a fairly recent rebuild.

So this weekend it happened while at the lake and I pulled all the plugs and turned it over to watch gas be sprayed out of #3. Put the plugs back in and it fired up.

It seems like an obvious carb issue here, but I've been through these carbs many times. Dipped and rebuilt. One thing to note though is the engine never really runs good. Sounds like it has an intermittent misfire from 2000-4200 rpms. WOT runs smooth. It doesn't idle very well either. Last weekend I set the timing per Seloc manual. The timing was off a bit but under a load it doesn't appear to run any better. Any ideas?

Re: won't turn over - cylinder 3 full of gas

Normally....and I use that word with hesitation...that much gas in a cylinder is from (a) float adjusted too high (b) bad float needle/seat (c) sunk float (d) float sticking open.
From the sometimes works/sometimes doesn't, I would probably first look at a stuck/misadjusted float. That would also account for poor running as that cylinder is loading up at idle but not so much at WOT.
Hope this helps and good luck.

Gary

Re: won't turn over - cylinder 3 full of gas

Check the fuel pump diaphragm, If the tank was pressurized while sitting it could push fuel through a leaking diaphragm into #3 where the pump gets its vacuum/pressure pulse.

Re: won't turn over - cylinder 3 full of gas

When I did the carb rebuild, the floats required no adjustments.

The fuel pump is new.

Re: won't turn over - cylinder 3 full of gas

tal said:

When I did the carb rebuild, the floats required no adjustments.

The fuel pump is new.

Click to expand...

I agree with the check the fuel pump recommendation.
I had a bad diaphram on the exact same pro50 motor and thats exactly what it did, flood the #3 cylinder thru the base vacuum port that runs the fuel pump. Did the problem start when the new fuel pump was installed? Was the pump new or rebuilt? There are 2 very similar looking diaphrams in that pump that cannot be interchanged.

Re: won't turn over - cylinder 3 full of gas

The pump is a fully new unit. I say new, but it was probably put on over a year ago but hasn't had much use.

Thing is, I used it Saturday and it sat with no problems. Used it Sunday with no problems, until the afternoon fish. When I went to launch it wouldn't turn over so I pulled the plugs.

Do you think the pressure that builds in those steel tanks can force enough pressure up there to damage the pump? When the tanks get bounced around they build up pressure and I relieve them from the cap. Similarly, when the temps drop outside they contract.

Re: won't turn over - cylinder 3 full of gas

from what I have seen all tanks now a days need to be vented and should not build up pressure unless you close the vent manually. A pump diaphragm can go bad at any time and especially if you have a lean sneeze or pop