Prop for 75 horse merc

[Cliff Rogers]

Need a ss prop for my motor prop that was on it was a aluminum 12.5x23p it is trash now due to a log in lake I want a ss prop but don't know what size to go too

 

[Bob Bourget2]

The motor should run between 5200-5500 rpm at wot..if you are "propped" to turn within this range, your present prop pitch is accurate. I might recommend the new SPITFIRE 4 blade aluminum prop. GREAT results without Stainless Steel prices.

 

[Cliff Rogers]

Ok man thanks got one more? I got a 13.5x20p ss gave to me will that prop work or u think it will over rev the 23p I had would only turn 5100 wot and top speed was around 41 will this new prop get me more top speed or hurt me on speed and take off

 

[Bob Bourget2]

Won't really know until you try it! Give it a go and see what she'll do!! Do NOT let it rev over 5600rpm......

 

[Cliff Rogers]

Ok will do thanks

 

[Cliff Rogers]

well the 20p didnt NOT work half throttle and was at 5500 so i gotta go bigger i think a 22p may be the ticket. with the 20p when i would try to take off quick it would blowout as well. if my math is correct isnt every pitch make u go up or down 400 rpm if so if i get a 22p that should put me at around 5400 to 5500 at wot if im wrong correct me but once again thanks for all the help

 

[Bob Bourget2]

21P SPITFIRE........you should see approx 5300-5400 with this change and a GREAT holeshot.....

 

[Cliff Rogers]

Ok I got a 24p ss and it works great but I now have a weird sound in lower unit when I put it n gear at idle a some what grinding sound but when taking off it quits the sound what would average cost to rebuild lower unit I can feel the grinding sound in steering wheel and I can hear it any thoughts or answers

 

[Bob Bourget2]

24" pitch....what is the WOT rpm???? Sounds like it is too much prop......

In any regard...the "rattle" that you are picking up is the clutch dog vibrating. Won't do any harm. They make a special spring loaded flo-torq hub for the cases with the noise.

 

[Cliff Rogers]

I'm getting 5300 with this 24p prop and comes out great at tops out at 46 on gps I thought it would be to big as well but it works great other than the noise it's making when in gear and idling but like I said once I give it gas it quits the noise. My old prop was a 23p and it did good but this one gets me alittle more top end and I lost just alittle take off nothing that I could tell much

 

[Bob Bourget2]

It isn't a merc prop is it? The pitch / rpm correlation does not make sense.....

 

[Cliff Rogers]

It is a lazer 2 prop and it is stamped 24 p I thought it would be to high of pitch also but it works great one ? I do have is this my motor says max rpm is 5200 but very one is telling me to run it at or close to 5500 why 5500 if max is 5200

 

[Bob Bourget2]

Has it been rebuilt? Yes, the 5500 rpm recommendation is correct. The powerheads for the 75 and 90 are identical except for carb venturi size, and the 90 is rated for 5500. It WILL let it live longer, due to the fact that at part throttle, the engine load is somewhat less, helping with any pre-ignition issues that could crop up.....

 

[Cliff Rogers]

No the motor has not but the prop I got has indeed been reworked so maybe they changed the pitch when they reworked it