Prop help

[Terry874]

Hi I’m new to boating and this forum. I am looking at purchasing a new prop for my boat to optimize performance. My boat is a 16 foot crestliner that weighs around 2000 lbs loaded. It is a aluminum.My motor is a optimax 90.

Current prop is a 3 blade aluminum 12.5 inch 23 pitch mercury.

When I accelerate for a dead stop I am hitting my rev limiter slightly.

At wide open throttle the motor will not climb over 5100 rpm. Top speed is just under 40 mph with my wife and 2 kids.

Any suggestions would be great

 

[jimmbo]

40 mph on a heavy 16 ft with only 90 hp is very good. What is the WOT rpm range for that engine?

 

[cassabby]

Terry, I have a very similar Crestliner. I have a Nordic 1500 (15") Deep V with a 120 hp Force by Mercury. Currently loaded for fishing 2- people and full of fuel and gear best I can spin is a 13.25 X 22P SS Lazer 3 blade at about 5250 to 5300 RPM. That 12.5 X 23P Aluminum is a lot of Prop Pitch for your Merc 90 Optimax. Before you buy your next prop you need to identify why you rig is suffering from spin out or massive slippage at hole shot. Possible look into's are Motor mount height, Spun inner hub, over trimmed motor out of the hole I am currently mounted in the 3rd hole from top. Bottom of boat runs even to bottom of cavitation plate. Your next prop choice should be a bit larger diameter say 13.25 and you pitch should go down by maybe 2 say 21P. That is still a lot of Pitch your Merc 90 Optimax. Between my buddy and I we have 5 prop choices 19P thru 22p plus 20P 4 blade. 22P best for my rig 20P 4 blade best for his. Good Luck !

 

[Terry874]

Hi thanks for the replies. The wide open throttle range is 5500-5700 I believe. I did move my motor up 2 holes on the weekend to see if I would gain some rpm with my setup. It seemed to plain a bit quicker and gained a bit of speed. I have access to a 19 pitch 12.75 aluminum prop I can try but I was thinking it would rev quicker on take off and hit the limiter more?

 

[Terry874]

Also I wanted to ask what you meant by spun the inner hub? I’m still learning regarding boats.

thanks