Cobra 5.8 Runs Badly in Water Only

[jack383]

Have a 5.8 Cobra in 24 ft Bayliner. Runs great on ears but rough in lake. New plugs, points, fuel filter, carb rebuilt. Mechanic gave up.

 

[alldodge]

Have a 5.8 Cobra in 24 ft Bayliner. Runs great on ears but rough in lake. New plugs, points, fuel filter, carb rebuilt. Mechanic gave up.

Howdy

Has anyone done a compression test?

 

[bruceb58]

Does it idle the same? How does it run differently? Are you talking about when the engine is under load?

 

[Maclin]

What is the recent history of maintenance on this? Has it ever run correctly for you? If so, what was the last thing done to it, that kind of thing.

 

[dshakhba]

I have the same issue, I'm thinking its a fuel pump issue. Not getting enough gas under load.

 

[Jammer864]

Make sure there is nothing obstructing the exhaust. If there is an exhaust flap broken off and its blocking the exhaust to the drive, bingo, no power. Revs up beautifully but no power under load.

 

[Lou C]

Also replace the anti siphon valve on the gas tank if it's original. I had this problem with my '88 4.3 Cobra.
The engine would start and run and would rev fine in neutral with no load but would not plane out the boat. Make sure the ESA system is not staying engaged after shifting into gear. It is only supposed to engage (lower the idle from 600-->450 or so) when shifting from in gear to neutral....

 

[bruceb58]

OP hasn't been back since his post back in September.