99 dt225 running on 5 cyclinders

Ghlacy · #1 (**permalink**) 06-27-2010, 10:22 AM

Since the start of this years boating season my engine has only been running on 5 cyclinders. Every once in a while it will fire on all 6, but only for a moment. I replaced all the plugs at the beganing of the season. Last year I checked the compression at it was good and pretty even between the cyclinders. I don't remember what the psi was.

Any ideas? Plug wires? Coil?

Thanks for the help..

Ghlacy · #2 (**permalink**) 06-27-2010, 04:34 PM

Just got back from a ride and it seemed like it has gotten worse. It was only running on 3 or 4 cyc for a while and then started running better.

mitch · #3 (**permalink**) 06-27-2010, 09:41 PM

test your plug leads

Ghlacy · #4 (**permalink**) 06-29-2010, 12:40 PM

I pulled the plugs and they were really gummed up. I had just replaced them back in April. I went ahead and replaced them again and checked for spark and everything looked good. But it is still not running right. So I think it is either a fuel issue or a compression issue.

At WOT it will only turn about 3200rpm or about 9 knots. After about 20 minutes of running like that it will start to hit on all cylinders and it will speed on up. It seems to stay that way until you stop and let the engine cool.

Any ideas? Sounds to me like low compression until it heats up and the piston expands.

mitch · #5 (**permalink**) 06-29-2010, 08:45 PM

well do a comp check also check fuel pumps are not leaking into crankcase and flooding engine