Pontoon Boat & Deck Boat Forum

First time I have had the oppourtunity to travel a distance at WOT but found my best speed was at 6000 RPM vice 6300. It has a stock Merc prop.

It should not be that way unless your hub is slipping. I could understand it if it is not much faster at wot, but not slower.

I take it the GPS is running in KPH instead of MPH with 90 hp.

I bet the prop is cavitating a little bit at WOT. Did you try to bring the trim down a little to get it to bite at all?

Bryden24shp wrote:I bet the prop is cavitating a little bit at WOT. Did you try to bring the trim down a little to get it to bite at all?

It could be cavitating a little, I was seeing about 29mph at 6300 rpm, I trimmed up and down but just lost speed both directions so that was as fast as I could get it at WOT. As I slowed down the rpm a little it picked up .2-.3 mph.

And, no I do not have my GPS set on KPH. I am in the ballpark of what the dealer said I would get with underskin and lifting strakes (their version of perfomance package).

When you are running WOT, have someone steer for you and run back and see how far the prop is in the water. Look at the cavitaion plate on the L/U and see if it is running out of the water. With the new prop I just ran, the cav plate was about 3" out and I could hear the props ears slapping the water. If you are little too far out, it will ventilate.

Bamaman wrote:I take it the GPS is running in KPH instead of MPH with 90 hp.

I think 29.2 is believable.


Sounds like it's starting to suck air at the higher RPM to me too.