Questioning Dealer

[LarsonSenz]

Went into the dealer for a 4 blade aluminum to play with before I purchase a stainless. Dealer gave me a 14.5x17p and I think its going to be under propped. Before I can get back to the water and test and to save me a trip back to dealer I wanted to ask here.
2008 Larson Senza 206
21' long
3150 dry, 3550 loaded
Volvo Penta 5.7 Gi
SX drive 1.51
WOT 4500-5000
Currently on a 14x19 3 blade around 4600 RPM
Mostly going to be used for water sports and sunset cruises

Any input would be appreciated.

 

[QBhoy]

Depends what 4 blade it is and what the 19” 3 blade you had on previously was, I’d think. I will be 50/50 if it’s on the limiter or not, I’d think. Or it could be just perfect for you. Depends what you’re after too.

 

[Scott Danforth]

first welcome aboard

by the limited information you posted, you should be good

however for water sports, I normally like a lower pitch and control the revs with my right arm. There is no such thing as one prop does all.

 

[LarsonSenz]

Current prop is a Turning Point 3 blade 14x19 hitting just under 50mph around 4600 RPM WOT. As speed is not a big concern for me I'll give the 14.5x17p 4 blade a try. I'd rather not hit the limiter but if my research is correct I should similar to the same WOT RPM just a little slower. Really just looking for a better holeshot and holding on plane when the little ones wakeboard as they do tend to still like it slower.
Thanks for the responses.

 

[Cortes100]

I'd try the 17P 4 blade and see what happens. If your engine is good for 5000 rpm, you're still under by 400 the way you're running now. Worst case scenario, watch your WOT rpm.
Every prop brand is a little different when it comes to raking, cupping, etc. Plus prop technology has changed a lot in the last few years. I always stuck with the Merc brand props, so it was very easy to compare products. A 4 blade doesn't mean you have to drop pitch. FWIW, a Black Max and Spitfire, both in the same pitch did not change any rpm's or mph. Just that the 4 blade performed way better across the board.

 

[Texasmark]

Current prop is a Turning Point 3 blade 14x19 hitting just under 50mph around 4600 RPM WOT. As speed is not a big concern for me I'll give the 14.5x17p 4 blade a try. I'd rather not hit the limiter but if my research is correct I should similar to the same WOT RPM just a little slower. Really just looking for a better holeshot and holding on plane when the little ones wakeboard as they do tend to still like it slower.
Thanks for the responses.

A lot of TP props are ported....hole under the leading edge of each blade. This is a hole shot enhancer as it lets the engine rev faster in the shot to get HP up faster. If it is in fact ported and your new prop isn't you probably will have a worse shot even though you dropped your pitch. Adding a blade and dropping 2" could overcome the loss of ports if the new prop isn't ported......if it is ported......hang on!!!! Grin.

Dropping 2" will increase your rate of HP rise but the 4th blade will bite more water giving you more thrust if the engine can deliver the HP necessary to drive that increased load on it. That's the neat thing about ports. They unload the engine, not load it and since HP drives the prop shaft/prop for your thrust to push the water, and HP = torque x RPM basically, torque is engine design and the faster you can get your HP to rise the faster the shot....for a given set of conditions.

I like my ports to give me about a 1k jump in RPMs (amount determined by hole size) in the shot over an unported prop and I currently have 3 or 4 TP Hustlers, all ported by design. Rule of thumb on this forum is 150-200 RPM change per inch of pitch change..........