No power, barely will plane

[suds1421]

I have a 1994 OMC 5.0 carb motor. It will start and run's okay in neutral on muffs. It's hard to tell because the motor isn't under a load. It starts right up.

When I put it in the water and take off it has very low power. It won't rev up above 3000rpm. 2800 RPM is about WOT. It will barely plane out. I haven't added fuel and it ran fine on this tank of gas a week ago. I followed the ignition test from the four winns service manual. The coil has battery voltage at the positive side and 5v at the negative side (as expected). When the tooth of the distributor top gear is at the ignition coil sensor the negative side as battery voltage.

The engine also seems to run rough most of the time when in gear and above 1800 RPM.

One weird thing if you run the trim pump the roughness goes away and the engine surges. Seemed like I had full power when trimming up or down.

Any help would be appreciated.

Thanks, Jeff
1994 four winns horizon

 

[suds1421]

Is this the correct wire placement on the 1994 OMC 5.0 carb prestolite distributor cap (1994 four winns horizon).

My cap has been replaced. The firing order is 1 3 7 2 6 5 4 8. I verified by tracing the spark plug wires all the way back to the plugs.

My question is if the number 1 wire is indexed correctly. I have attached a hand made diagram where 1 is more towards the stern and 6 is more towards the bow. The number 1 plug wire is just counter clock wise from the stern pointing hold down screw.

Does that seem correct?

 

[Scott Danforth]

Guessing you have a Ford motor

#1 is where the rotor is when the motor is at TDC on cylinder #1

 

[suds1421]

I'll try to time it in the morning and see how it is.

Does anyone have thoughts on how /why adjusting the trim would make the motor run better?

 

[Scott Danforth]

Either its changing loading slightly, or more likely, the higher current draw from the trim motor is arcing across a bad batter cable connectuon somewhere and momentarily raising voltage to your ignition

 

[jimmbo]

2 bbl or 4bbl carb? If 4bbl, the secondaries may not be opening. Reasons, choke not fully open, gummed up linkages. Timing not advancing.

 

[suds1421]

Update: The plugs were fouled from a previous no start issue. Replaced the plugs and it ran well yesterday, will be taking for a further test drive soon.