I need some info on the right Propeller

[Ace1948]

I just installed a 1976 Mercury 85 hp on my 24 foot pontoon boat and I am not
sure if it has the correct Propeller.The one on this motor is a D3X13.25X17R. I don't know much about Propeller any help would be appreciated. This motor came off a 15 foot fiberglass runabout.

 

[Gomer50]

Re: I need some info on the right Propeller

I would suggest you take the boat out and test,if I am not mistaken that motor needs to be able to reach 4800rpm to 5300rpm @ WOT (wide open throttle) as to not harm the Motor. Not being able to reach those RPM's lugs this Motor and will cause damage.I am guessing a 17 pitch prop on a 24 foot pontoon is a little much.Dropping a pitch in prop size increases RPM approx. 200 RPM adding a pitch size drops RPM approx. 200 RPM.Good luck and happy boating..

 

[Maxz695]

Re: I need some info on the right Propeller

don,t know much either but I have a little engine on a longer boat 17.5 feet 40 hp I went from a 12 p to an 11 p because I was only getting 4800 5000 max rpm I was informed i should be getting 5200 5500. I lowered the engine to as close as i could get the LU tail even with the bottom of the baot and i,m waiting on waterpump parts before i can test. if you give youe RPM at WOT it might help determin if you even near the range of rpm you should be getting. Running at less tha peak rpm strains the engine and as far as I can see takes a toll on the driveshaft splines.

 

[daveswaves]

Re: I need some info on the right Propeller

I would suggest you take the boat out and test,if I am not mistaken that motor needs to be able to reach 4800rpm to 5300rpm @ WOT (wide open throttle) as to not harm the Motor. Not being able to reach those RPM's lugs this Motor and will cause damage.I am guessing a 17 pitch prop on a 24 foot pontoon is a little much.Dropping a pitch in prop size increases RPM approx. 200 RPM adding a pitch size drops RPM approx. 200 RPM.Good luck and happy boating..

Gomer is correct, that prop is too tall in pitch for a 24 foot pontoon boat. It may have been too much for the run about it was on. I would start at a 15 P and possibly come down to a 13 P to get the rpm up over 5000 at wot. To put things in perspective I run a 17P on my aluminum bass boat with a 1976 Merc 1150. Puts me right in the rpm range. Most marinas will let you try a prop, especially if you are going to buy the winner.

 

[Ace1948]

Re: I need some info on the right Propeller

Thanks for all the help this will help me get the right prop.