1986 mercruiser 350 carborated

[bzawart]

I jut recently purchased a 1986 formula f3ls it has a mercruiser 350 and mercruiser drive I believe alpha one. It runs great sometimes but soon as it gets to 3200 rpm and I push it to 4000 rpm it starts missing. I replaceg distributor, plugs, wires, fuel filter, fuel water seperator, I replaced rotor and also that part inside distributor I guess like a pick up coil. Also cleaned and checked the check valve on the tank. Redid all wires to coil and ends. I'm stumped I don't know what to do. I did notice that the rear two plugs closest to motor were wet with gas when I removed the old ones. I don't know any help would be great thank you so much.

 

[Bt Doctur]

Re: 1986 mercruiser 350 carborated

A compression test with the throttle wide open and post readings
A cylinder balance test , with the motor running remove 1 sparkplug wire at a time and note the rpm drop

 

[TiredoleBoy]

Re: 1986 mercruiser 350 carborated

Sounds like the advance is sticking.Pull distributor cap and see if the weights and springs are rusted. Also check for vacuum drop at the dashpot.

 

[bzawart]

Re: 1986 mercruiser 350 carborated

There is no weights and springs on it. This has the thunderbolt ignition on it and I replaced the piece in distributor that the rotor goes through it"s like a pickup coil. The motor only has about 60hours on it from an overhaul. This didn"t happen until I changed the plugs and wires and cap and rotor. I don"t know I didn't knock anything off or do anything different but it ran fine before I did the tune up I should have never touched it I guess. So I was just looking for some input..

 

[Bt Doctur]

Re: 1986 mercruiser 350 carborated

Sure you got all the plug wires on, in the correct firing order

 

[oneti mofugus]

Re: 1986 mercruiser 350 carborated

i had the same issue, but my boat was repowered from the previous owner....turned out i had a V6 rotor in my 8 wire dist. have you checked the timing with a timing light? you would at least be able to see if it is advancing correctly...check your manual to make sure, but i believe you should be seeing 28-32 degrees...don't quote me on that