1994 200HP full throttle is only 2,500 RPM

[Hubboat]

OK, so I took the boat out for the first time today (with 200HP I bought used... sat for couple years prior).

Idles GREAT, no throttle needed to start, nice and responsive right up to 2,500 RPM under load where it goes no further. I did get it to hit 4,000 around a turn where it stayed for a bit, then would go no higher than 2,500 again. Tried choking during this, saw no change.

In neutral it will rev to 5,000+.

-Compression is exactly 120 on all 6-cyl (just checked this today).
-I rebuilt the carbs, put together exactly as they were.
-Strong spark.
-Timing is correct.
-Voltage is correct.
-Reaches normal operating temp.
-Correct size prop for the boat.

Any ideas would be great, at somewhat of a loss here. I may slap the carbs from my 175 on to eliminate them as a possibility.

I did pull one of the temp sensors to silence the buzzer (bad sensor), could this cause a limp mode or something?

Thanks,
John

 

[CharlieB]

Re: 1994 200HP full throttle is only 2,500 RPM

dva test the stator following the directions found in CDIElectronics free ignition troubleshooting guide available thru the link on their Support page.

A weak hi speed stator winding will limit ignition voltage and RPM above 2500.

PROVE the fault as there is NO RETURN on electrical parts.

 

[Hubboat]

Re: 1994 200HP full throttle is only 2,500 RPM

Thanks for the reply, would that only limit RPM at load? It will free-rev in neutral over 5,000 RPM.

dva test the stator following the directions found in CDIElectronics free ignition troubleshooting guide available thru the link on their Support page.

A weak hi speed stator winding will limit ignition voltage and RPM above 2500.

PROVE the fault as there is NO RETURN on electrical parts.

 

[CharlieB]

Re: 1994 200HP full throttle is only 2,500 RPM

Right, load drops intake vaccuum allowing a lot more air/fuel into the cyl, which under compression increases voltage necessary for spark.

Prove the stator bad before ordering another.

DVA adaptor can be built quite cheaply, diagram and parts list are somewhere in the Merc forum.

 

[Hubboat]

Re: 1994 200HP full throttle is only 2,500 RPM

So I swapped the stator from my other motor, saw no change.

Then I pulled the red wire from the black square box on the top port side of the engine (some sort of timing box), and the engine ran great.

Swapped the one from my spare engine over and it's all good.

5,500 RPM at 41 MPH (22' Angler walkaround).

 

[NFA]

Re: 1994 200HP full throttle is only 2,500 RPM

So it was just a faulty red wire the whole time?

Incredible. Good job Hub.



SSS

 

[Hubboat]

Re: 1994 200HP full throttle is only 2,500 RPM

So it was just a faulty red wire the whole time?

Incredible. Good job Hub.

SSS

Basically, once red wire going to box was disconnected engine ran fine. I replaced box with a known working one.

 

[CharlieB]

Re: 1994 200HP full throttle is only 2,500 RPM

Idle stabilizer, take it off and drop it over the side in deep water.

Merc discontinued this part, sometimes when they go bad at WOT a rod will come out the side.

Reset WOT timing at 23 degrees once the stabilizer module is gone.