Rough idle and slight miss at higher revs

"You should eliminate the obvi

"You should eliminate the obvious first. Besides, filters are easier to clean and cheaper to replace than distributors, aren't they? (well, with Volvo Penta OEM parts you never know... )"

"Yeah I was also thinking abou

"Yeah I was also thinking about swapping the coils and distributors and taking it out for a another run. If the good coil/dist from the port motor makes the starboard motor run good and the port motor runs like crap I will know whats up. If not then I am onto something else, at any rate I will know whether or not to order another one.

Only one issue, my brother cant find his timing light so I am leary of yanking the distributors until I get my hands on one.

I have a short overnight trip planned for Saturday...tick tock tick tock. Hehe supposed I can run it at 1500rpm the whole way. I will still go twice as fast as my buddies sail boat hehe."

"Yeah, but your fuel consumpti

"Yeah, but your fuel consumption per mile at 1500 RPM must be sorta high, eh? Planing boats don't like to be opearted as displacement boats. "

"Options Options Options, chea

"Options Options Options, cheap ones I am runnin' out of... Besides I still think the gas is kinda suspect anyway, its been sitting since last Sept."

"When were the plugs last chan

"When were the plugs last changed? Recommend doing it now, and checking the old ones for color.

JEff"

"Changing plugs is one of the

"Changing plugs is one of the first things I did, they were in good shape though although they were fairly black and seemed kinda wet in general, a bit gasy too."

""fairly black and seemed

""fairly black and seemed kinda wet in general, a bit gasy too"

Hmmm sounds a lot like my dog!

It also sounds a lot like my situation when I checked the compression. Could be a timing or ignition issue. Looks like your getting fuel."

"Yeah I need to get my hands o

"Yeah I need to get my hands on a timing light, going to check the timing and if its ok then swap the coils and distributors and see if the issue swaps with them. However I am wondering if it was timing if it would be as random as I am seeing. Also I can rev the motor to a constant 3800rpm throttle only and the motor never skips a beat, its only when its under load... I would think that bad timing would be more consistently missing. I am starting to lean towards bad coil or distributor gear or distributor pickup. I wont know until I switch them over. Oh and I am going to check tonight if it has a filter in the carb."

Ok I finally figured out what

Ok I finally figured out what is wrong with the starboard motor.

Cylinder #3 has zero compression and the motor is running on 5 cylinders.

So that is why it runs rough at idle and when I wind it up a bit it almost seems fine. As for the misfiring that is happening when the boat is under load as the fuel air mixture is sometimes exploding in #3 but not correctly as its not getting compressed properly.

"Well, if the problem is due t

"Well, if the problem is due to a hole in the piston, that's bad; but if it is due to a lifter out of adjustment or a burnt valve, that may not be too bad.

Please let us know what you find."

"It's not a lifter out of

"It's not a lifter out of adjustment as we played around with those with no improvement. Although it could be a collapsed hydrolic lifter.

We also noticed quite a bit of oil on the deck of the carb under the air cleaners which would lead me to believe there is a fair amount of blow by on both motors.

My question would be is it worth replacing the head if I can get a whole rebuilt crate motor for 1400$ US, my brother thinks I should just buck up and spend 3k and buy two of them and switch them out in the winter...

Thoughts?

On a slightly happier note though I was able to get it up on plane and cruising nicely with only light misfire when getting up on plane and once I backed off the trim tabs. It only backfired 3 times in an hour of running 3600-3850rpm and pulling 26-29mph."

"Andrew, if you replace both e

"Andrew, if you replace both engines you know what you have; while if you don't, you will always have the doubt. If you want to keep the boat and you have the money, I think you may want to follow your brother's advice. In any case, blow-by is not a good sign."

"Well seeing as it is currentl

"Well seeing as it is currently running ok, I think I will just leave it be until the end of the season (unless one of the motors gives up)and take the heads off in the winter and have a look. I was really hoping I would get a boat that I wouldnt have to do this to but oh well at least I am learning a lot about my boat I used to race cars and work on Chevy small blocks and I am seeing a lot of similarities with these 4.3's so at least I am not totally useless.

Thanks for all your help everyone, especially you El Pescador!!

-Andrew"