Improving Top Speed

[KeyCutter]

Would like to increase top speed without loosing the good hole shot I have now. I think the three blade 14.5x19 prop I have now is right for my Sea Ray 180 3.0 Merc. WOT RPM is 4800-4900 with a top speed of 38mph. Should I be trying 4 or 5 blade props? And should I change the pitch when doing so?

 

[Scott Danforth]

Sell boat, buy boat with bigger motor.

You wont be able to gain top end without loosing the bottom end. Especially with the 3.0

 

[ahicks]

There MIGHT be a couple of mph left on the table, without killing bottom end performance - IF - you can find a local prop guy willing to work with you. Some of these guys are magicians! Just don't expect them to work for free....

This will be a hands on person to person deal. Expecting magic via email is not likely going to work in your best interests.

 

[Scott Danforth]

One thing that will help.....if you have a fin or tail bolted to the outdrive, remove it

 

[QBhoy]

4 or 5 blade will cause a decrease in top speed....generally.
A similar question was asked recently, with a similar boat and 3.0.
I advised trying a decent stainless like a laser 2.
At least three or four of the guys in my marina with similar boats and engines switched to a laser 2 and see a few mph difference above the standard black max. Running into the 40's and one guy manages 45mph in his maxum 17/18ft bowrider.

 

[KeyCutter]

Thanks, so it sounds like trying for more top end is a waste of money. So even though I'm ok with the hole shot, could that be improved with a 4 or 5 blade? And would I have to worry about going over my WOT rpm?

 

[jimmbo]

You have a small engine and it does remarkably well. You are over revving slightly, and an increase in pitch or blade area will lower the rpms. It would probably slow your holeshot.
Remove the Wife, Kids, Mother-in-law, especially the Mother-in-law from the boat and leave them ashore. Girlfriends and Mistresses can remain aboard. That will probably increase RPM enough to raise the rpms enough to allow 2 more inches in pitch and the holeshot will be similar due to less ballast

 

[Scott Danforth]

Skip the 5 blades and go up 2" in pitch max in a 3 blade, or try a 19p 4- blade. Either way, your holeshot will suffer

For me, i would leave it alone