1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

[Chance12]

Hi,
I tried everything!!! Rebuilt the carb, new fuel filters, fuel line, cleaned tank, non-ethanol fuel, points, condenser, coil, plugs. It runs perfect for a while. 30-45 mins. then out of nowhere it will start breaking up at higher RPMS and at the same time if you run any extra electrical load on the engine like( trim motor, blower, ect) it gets worse and almost wants to stall.
Please help if you have any ideas where to look.

Thanks

 

[alldodge]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

Sounds like an electrical issue. Chech your connections from the battery including the grounds. They all need to be clean and tight. While checking look for corrision inside the crimped connectors.

 

[Chance12]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

Ok, Where are these crimped connectors?

 

[alldodge]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

Ok, Where are these crimped connectors?

Crimped connectors are any connection which is crimped using a crimpping tool, such as many of the battery to engine connectors. Some manufactures solder connections others crimp the lug onto the wire. They come in small and large sizes. Electrical issues are hard to find. You may look at a wire and it looks great, then you pull on it and it comes apart

 

[Volphin]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

Sounds like the coil is breaking down as it gets hot. Check and clean the electrical connections on the coil, and her grounds then retest. Also measure the coil for 12v in while it is missing. If it's less, then the problem is electrical. If voltage is OK, the coil is shot, and can be confirmed by testing it with a multimeter.

 

[Chance12]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

Crimped connectors are any connection which is crimped using a crimpping tool, such as many of the battery to engine connectors. Some manufactures solder connections others crimp the lug onto the wire. They come in small and large sizes. Electrical issues are hard to find. You may look at a wire and it looks great, then you pull on it and it comes apart

I found a little corrosion in the ground by the starter. Checked all the conections that I could find. Hopefully I found it.

 

[Chance12]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

Sounds like the coil is breaking down as it gets hot. Check and clean the electrical connections on the coil, and her grounds then retest. Also measure the coil for 12v in while it is missing. If it's less, then the problem is electrical. If voltage is OK, the coil is shot, and can be confirmed by testing it with a multimeter.

I have tried two different coils. One orignal and one new Napa coil. 12volts at the coil when is runs rough. It will idle-2000 rpms perfect while it breaks up in higher rpms.

 

[thumpar]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

What ignition do you have? If it is still point and condenser with standard coil you should only have around 7-9 volts at the coil.

 

[Chance12]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

What ignition do you have? If it is still point and condenser with standard coil you should only have around 7-9 volts at the coil.

Yeah I should have been more clear. It does only have 8.5 volts while running. I put a jumper wire from the battery to the coil for a second to see if it would clear up....it didn't.

 

[dubs283]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

is the alternator charging properly??

 

[Chance12]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

is the alternator charging properly??

I think so the gauge says 14volts while running????

 

[heavy_breeze]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

Bushings in your distributor could be loose, or your timing belt is shot. Is your distributor bolt to engine not secured properly? Sounds like distributor/timing issue.

 

[thumpar]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

There is no timing belt just gears. Those don't usually cause any issues for the life of the engine.

 

[alldodge]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

It runs perfect for a while. 30-45 mins. then out of nowhere it will start breaking up at higher RPMS and at the same time if you run any extra electrical load on the engine like( trim motor, blower, ect) it gets worse and almost wants to stall.
Thanks

Still belive it is an electrical issue, I think the getting at running temp is just happens because it takes that long to show up. Did you ever restart the engine after this started happening? If so did it crank slower then normal and what shape is the battery in?

 

[stonyloam]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

Check your fuel tank vent, it may be plugged (creating a vacuum when you draw the fuel down) and reduce the amount of gas you can deliver to the engine. If it happens again try removing the gas cap and putting it back on, see if that helps.

 

[alldodge]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

Check your fuel tank vent, it may be plugged (creating a vacuum when you draw the fuel down) and reduce the amount of gas you can deliver to the engine. If it happens again try removing the gas cap and putting it back on, see if that helps.

Stonyloam - that sounds like a real good possability. Had a stand alone generator which did the same thing and about drove me nuts until I accidently found it.

 

[Chance12]

Re: 1984 Sea Ray 120 mercrusier sprotic misfire. HELP!!!

Check your fuel tank vent, it may be plugged (creating a vacuum when you draw the fuel down) and reduce the amount of gas you can deliver to the engine. If it happens again try removing the gas cap and putting it back on, see if that helps.

I have tried that and no difference. also when I fill the boat some gas will shoot out of the vent when the tank is full.