Intermittent RPM loss at WOT

[Robert Pitts]

I have an 89 1.6L. OMC sea drive on a 21' Wellcraft. I have been fighting this problem for two years now. The engine rpm drops from 4900 to 3000 rpm intermittently. When I hit the primer the rpm comes back to about 3700.
The carbs have been rebuilt twice, once by me and second time by mechanic. I have Installed new coils, powerpacks and voltage regulator. I added an electric fuel pump to the system. The throttle cables have been replaced. I have even bypassed the pumps and filters and gone with an external six gallon tank but still have the problem. It is extremely intermittent. I can run it for 5 minutes or get ten miles offshore before it drops off. Never been able to duplicate out of water. Any help will be appreciated

 

[Robert Pitts]

Re: Intermittent RPM loss at WOT

^bump

 

[Solittle]

Re: Intermittent RPM loss at WOT

I think your problem is still with the carbs. You said "When I hit the primer the rpm comes back to about 3700." That points directly to the carbs considering the other things you have done.

I have a pair of those (only 87s) on a 23' Wellcraft Fisherman model & love it.

Oh and if you are getting only 4900 at WOT you still have some work to do after you get this problem solved.

 

[Robert Pitts]

Re: Intermittent RPM loss at WOT

Thanks for the reply Solittle.
I agree that it still has something to do with fuel delivery, but It's driving me nuts. I checked all the fuel hoses under the cowling this weekend and all seemed ok but I replaced them anyhow. I haven't had a chance to run it in the water yet.

Here is another thing I tried the last time out. When the rpm dropped to 3000, I pulled the throttle to idle and then took it back to 3000. when I pushed the primer, the engine bogged down to 2600. I took it back to WOT and it was running ok (for a few minutes) when I pushed the primer there was no change in rpm's. Do you think there should have been?

The 4900 rpm at wot is partially due to changing the prop after this problem started. I used to get around 5200 with the old prop.

 

[suzukidave]

Re: Intermittent RPM loss at WOT

any chance there is water getting into the engine bay from somewhere and misting? my suzuki outboard tortured me with those symptoms for 2 years. It was a loose rubber cowl seal and missing rubber grommit in a hole in the engine base letting water mist in and bogging down the lower carb.

 

[Robert Pitts]

Re: Intermittent RPM loss at WOT

suzukidave,

I never thought about that. I will check those grommets as soon as I get home this afternoon. I'll post results tomorrow.

 

[Robert Pitts]

Re: Intermittent RPM loss at WOT

Well, I checked the grommets and all were intact and tight. There's another one I can check off the long list of things that could be causing this problem. How long is this list anyway!!!

I also pulled the carbs off last night and checked float settings. Again, all seemed ok.