1995 GT 40 problems

[polkaking27]

I had the engine rebuilt over the winter and got it back on the lake for the first time on Saturday. Engine runs fairly smooth but as I slowly increase the RPM's it starts surging around 2700 RPM. To be more descriptive, it will run at the regular rpm than drop down in RPMs violently, then right back up to the regular rpm. Each drop is about 1 second long, and even when I increase the throttle it won't let me get past this surging point.

It seems like it may be an ECM issue, or maybe fuel pump. Does this ring a bell for anyone?

Thanks

[Mamigacz]

Sounds suspiciously like its starving for gas. Is there anyway you could rig a fuel pressure gauge to see if the pressure drops when the symptoms happen? The gauge would need to be visible by you or a passenger while the boat was moving.

Unless, you can get it to act up in neutral? Does it only happen under load?

I'm assuming you have no engine codes, right?

[bhectus]

My old '96 did that same exact thing to a tee after I had the heads replaced. Turned out to be a faulty oil pressure sender.

[core-rider]

You said you had the engine rebuilt over the Winter... Did they overbore the cylinders? If so read this thread... http://www.planetnautique.com/vb3/sh...ck-in-the-face

You may have the same problem.

[Lewy2001]

That 2700rpm sounds like the SLOW (Speed Limiting Operational Warning) or "limp mode" is kicking in.

There is a separate oil and temp switches that activate this mode on the ECM for the GT40.