Prop selection

[tottav]

Here is what I have. A 2012 Lowe SF 214 W/ merc 115 four stroke. Boat ran horrible when I purchased it. I added aluminum skin under deck witch stopped the surging problem also added 8" jack plate witch now has a similar setback to the new models. That helped a lot, picked up several mph and handles much better. Finally a water glide (fiberglass 3 toon).

Now I'm trying to figure out the props. The boat is now running about 27 loaded w/ four adults and about 32 by myself witch is great. Here is the problem I'm getting lots of cavitation and rpm surging. Have tried several props a spitfire 15, vengeance 14 and a vengeance 15 w/ cup added. The 15 w/ cup runs the best but still is not correct. All the props are turning close to the same rpm 6000-6200 and surging to 6500.

If anyone has any advise I would love it.
Thanks

[RcgTexas]

Is the jack plate hydro or manual? Is it cavitating with the jack plate all the way down. If not lower it until it stops. Sounds like the prop is ok(by the speed and rpm) but not turning on the right plane to not cavitate.

[tottav]

It is a manual plate and yes it is lowered all the way down. With the plate raised some the motor would start to blow out when you give it a little trim.

[Stinger 88]

I have just finished propping a 2015 Encore Bentley, 223, 115 Optimax Pro XS, (Tritoon). Initial problems with the Tac not set correctly (Self corrected), started with a Vengence 13 went to a Vengence 18, Laser II 21 and finally settled with a Laser II 19. Motor actually sets back from transom rub rail 22" inclusive of a 6" manual Jack plate. Cavitation plate set even with the bottom of the transom pod. One person, 3/4 fuel load, Striper fishing gear, bimini up, 48 qt cooler, 20lb ice, case of beer,5400 RPM's, 38.6 GPS MPH, 13psi water pressure. Motor red line 5750 will adjust with motor height with the jack plate after seeing what cooler weather brings to motor performance.

[RcgTexas]

OK is the motor bolted in the lowest holes or up some?

[tottav]

Yes the lowest holes.

[RcgTexas]

OK (scratching his head) I'm wondering if the cavitation plate is just a little too high in relation to your transom. Try a looking along the cavitation plate and see where that line hits on the transom.

[tottav]

Here us a couple pics

[RcgTexas]

Well you were right the motor is all the way down. Wish you could lower the motor and then raise it by adjusting the jack plate.