Prop Help

[Grahamb]

Hey guys. I posted this in the prop forum and got some advice there, but I wanted to see what folks with a similar hull think.

I whacked my prop on some rocks while loading when the lake was low. I’m going to replace it but using this as a chance to re-evaluate if I have the right prop.

Boat - Crestliner VT 18 (Aluminum Mod V hull)
Motor - Mercury 115 Pro XS; 2.07 gear ratio
Current Prop - Black Max 17P Aluminum
Speed - 42-43 (gps)
RPM - 6100-6200 (on board analog tach); if I trim any more the RPMs jump to about 6400 but the speed drops to 39-40 and the boat feels like it bogs down.
Setup - Motor is in the middle hole.

This is my first boat, so I don’t have much to compare it to in terms of hole shot and handling. They feel fine. I’m not looking to move the motor any, but if I could eek out a few extra MPH that’d be great.

Note that when the boat was new we also tried a Spitfire X7 19P and the boat didn’t like that prop. We couldn’t get it turn it faster than 5100 RPMs (that was with the dealer trying various motor heights). That said; since then we’ve added some trim tabs because I was also having a porpoising issue which is now resolved. I’ve also since swapped a Maxxum for an Ultrex which is heavier.

Let me know what you think!

Thanks guys!

[Grahamb]

Answering my own question in case anyone searches. I tested a 19P Black Max, 17P Spitfire, and 19P Spitfire.

I've decided to keep the 17P Spitfire. The 19P spitfire was maybe a hair faster (less than 1 mph) but it would also blow out occasionally while just going straight on calm waters. It was strange. Everything would be stable, I wouldn't turn or touch the throttle or trim and it would blow out. I may be able to address that with adjusting motor height, but I wasn't interested in going that route. With the 17P I've gained a couple mph at the top end over my three-blade and can now hit 45; maybe even a little more.

One other note that I realized in my research. Mercury also makes props under the name Quicksilver. They use the same molds as the Mercury props, but they tend to be a bit cheaper; note that they don't include a hub kit but even factoring that in they are still cheaper. I was able to reuse my old hub kit. I used the Mercury names above but I actually tested the Quicksilver Black Diamond (Same as the Merc Black Max) and the Quicksilver Nemesis (same as the Merc Spitfire).

[tcesni]

Is your ProXS the 2-stroke or the 4-stroke? I'm assuming its a 4-stroke or you'd be over revving the motor.

[Grahamb]

Is your ProXS the 2-stroke or the 4-stroke? I'm assuming its a 4-stroke or you'd be over revving the motor.

Yup; 4-Stroke.

[GeauxTide]

Love my X7. I've a 19" because of My Optimax. Handling is outstanding. You'll be extremely satisfied.