1999 VMAX 200 Not Develpoing Full RPM

[Groovius]

I am still having touble developing full RPM. I am running a 14 x 17 4 blade SS PowerTech on a 26 foot Pontoon (2600LBS). It feels as though I am getting some spark retard or hitting a rev limiter. Should get to about 5600-5800, but only developing 4200, with some surging. Is it possible my ECM is coming into play here? I'm completely out of ideas...

Also, please forgive the typo above, I realized that my posts might carry more credibility if I could spell! Thanks for any and all suggestions.

Jim

[boats.net]

Probably need to use a smaller pitch prop, try a 13 pitch aluminum prop.

[Groovius]

I bumped down to a 15 pitch, with no difference in RPM. It still feels like I am hitting a rev limit or spark retard.

Very odd...

[mitch]

but you have gone up ...........14 up to 15 ?

[Groovius]

I've been everywhere between 21 P and 15 P, in the 14 - 15.25 Dia range. No real differences. That's whay I am thinking electronics. I'm realtively new to OB tech stuff, but have a firm understanding of automotive. Am I on the right track? The only other thing I can think of is I replaced the lower unit, and may have a different gear set than what was on there originally.

Am I even in the ball park?

[boats.net]

If you are running a VMAX motor on a pontoon you will need the smallest pitch prop you can find and it still may not be small enough.

[Groovius]

Thanks. The only reason I keep going back to the lower unit is that before I replaced it, I got 5600 with the 15.5 x 17 3 blade. So is your thought process that I am over-loading the motor with this 14 x 15, 4 blade? I get similar RPM results with my back up 15 x 17, 3 blade. This is a 2600 lb boat that originally had a 225 on it.