Engin RPM's

[patrickruszkiewicz]

On my boat I have 1997 200 hp Evinrude Ocean Pro and a 9.9 hp Johnson 4-stroke trolling motor. The 200 starts easily in the morning and gets up on plane at around 3500 rpms. After running for a few minutes it hesitates (looses a couple hundred rpms) them gets back to what I was running at (usually between 4200 and 4500 rpms). This might happen a couple of times until I reach my fishing grounds. I then use my trolling motor, without any problem, for several hours. When I restart the 200 hp motor the rpms run up to about 3000 and won't go any higher (not enough for planning) for several minuites until the rpms suddenly rise and I can travel at any rpm I wish

I use Stabil when I fuel up. I've double clamped all gas line connections and checked all the lines for wear yet it still feels like I'm sucking air.

Is there anyplace else I should look?

 

[glengold]

Re: Engin RPM's

fuel filters or fuel pump may be bad. did you try pumping the ball while underway?? I had this problem and replaced both the clear inline fuel filter before the ball, the ball itself, and the factory fuel filter under the cowling to get it to work. But before i did all this i determined it was a fuel delivery problem by having someone else drive and go back there and pump the ball. the motor wouldn't die if I was back there pumping the ball

 

[jtexas]

Re: Engin RPM's

'97 evinrude is carbed not FICHT, right?

You are running both motors off the same tank? In your setup, is it possible that the kicker is draining fuel from the 'rude carbs? Have you verified that the main motor isn't losing prime when you switch the tank over to the kicker?

a VRO pump will dump more oil into the mix if the fuel line sucks air - smokier exhaust.

done any recent maintenance?

When in doubt, start with compression test and spark test.

 

[raczekp1]

Re: Engin RPM's

hi.kruszkiewicz?sounds like from Poland?

 

[patrickruszkiewicz]

Re: Engin RPM's

Both Filters were replaced. The bulb was pumped when the rpms wouldn't go above 3000 without effect.

 

[patrickruszkiewicz]

Re: Engin RPM's

My marina thought I might have the kikker draining the big motors carb so he installed a 2-way switch. This didn't solve the problem.
Both filters have been replaced and the plugs checked (they're clean).

 

[jtexas]

Re: Engin RPM's

I guess you checked the tank for water/debris.

Compression and spark test (not a "spark plug" test) are next.

Use an inline spark tester, set the gap for 7/16", clip it to the engine block, attach the plug leads (one at a time) and look for a strong blue spark while cranking. If it can't jump a half-inch gap in the open air without a spark plug, it's not firing in the hole under heat & compression.

If you can replicate the symptoms at the dock or on the trailer, do the spark test while it's not making full RPM.

If you have good compression & spark I'd rebuild the carbs. Possible you might have a float or two getting a bit sticky.

 

[patrickruszkiewicz]

Re: Engin RPM's

Thanks for the help. I'll test the spark plugs next. I hope I don't have to rebuild the carbs. My only problem with this is that when the engine runs I can get it up to 5000 rpms (a little hot for crusing) without a problem.

My 2 year old 4 stroke has no problems running for hours so I really don't think it's a fuel delivery or contaminate problem.

 

[jtexas]

Re: Engin RPM's

Is there any chance it could be going into SLOW mode? Rule it out by running it with the temp switch disconnected, but first make dang sure it's not overheating.

Unrelated to your present problem, but I wonder if you might be a little overpropped. Isn't that motor recommended to run 5500 to 6000 at WOT? Better to have it at the top of the recommended range; if it doesn't get there, it's lugging at pretty much all throttle settings.

 

[patrickruszkiewicz]

Re: Engin RPM's

The origional owner tried 2 other props (which I have) to try to maximize preformance. He went back to the one that came with the motor. Isn't 5500 to 6000 high for a 2-stroke?

 

[jtexas]

Re: Engin RPM's

A lot of the OMC motors run that high; not sure about yours in particular, is why I put it in the form of a question. I wouldn't recommend changing it until you can find out for sure. You can get a definitive answer on the "Prop questions" forum.

 

[wilde1j]

Re: Engin RPM's

Your motor should turn 5800 @ WOT. If it doesn't, prop it to do that.

 

[jonesg]

Re: Engin RPM's

On my boat I have 1997 200 hp Evinrude Ocean Pro and a 9.9 hp Johnson 4-stroke trolling motor. The 200 starts easily in the morning and gets up on plane at around 3500 rpms. After running for a few minutes it hesitates (looses a couple hundred rpms) them gets back to what I was running at (usually between 4200 and 4500 rpms). This might happen a couple of times until I reach my fishing grounds. I then use my trolling motor, without any problem, for several hours. When I restart the 200 hp motor the rpms run up to about 3000 and won't go any higher (not enough for planning) for several minuites until the rpms suddenly rise and I can travel at any rpm I wish

I use Stabil when I fuel up. I've double clamped all gas line connections and checked all the lines for wear yet it still feels like I'm sucking air.

Is there anyplace else I should look?

Ignition timing advance mechanism may be getting hung up.