Prop Pitchees??

[BIGDODGEJOHN]

I HAVE A 305 MERCRUSIER. WITH A 898 LOWER. AT FULL THROTLE MY BOAT RUNS AT 5400 RPM. MY FACTORY MANUAL SAYS THAT 4600 RPM IS THE MAX RPM TO RUN. I HAVE A 19 PITCH PROP ON THERE NOW WHAT PITCH WOULD BRING THAT DOWN,BUT STILL ENOGH TO PULL A SKIER WITH A FULL BOAT? THANX

 

[oops!]

Re: Prop Pitchees??

that depends on a lot of factors.....
weight, horse power, drag and hull shape....

however for every 1" of pitch you go up you will loose approx 200 rpm.
you are now seriously underpropped, unless mods have been done to the engine.
you want to find the prop that gives you the best of bolth worlds.

hole shot/pulling /plaining power. and top end

you might want to try a few props from a local marina (some will let you try them first)

you will need a accurate speed mesuring system...(gps) and a tach.
go out have fun and get the prop that does what you want.

cheers
oops

 

[Haut Medoc]

Re: Prop Pitchees??

What he said......^^^^^^
Athough A 14.25 X 19 should have you in the ballpark......
You should post your question on the prop forum, btw......​

 

[JustJason]

Re: Prop Pitchees??

the first thing you want to do is get a shop tach/backup tach, and hook up up directly to the engine and not through the boats wiring and verify your actual rpm

 

[wire2]

Re: Prop Pitches??

Re: Prop Pitches??

A boat drive is comparable to a car with a 1 speed transmission. You have to choose a gear that will allow you to get rolling from a stop and not over rev the motor at speed.
Your outdrive is probably 1.5:1 but you may want to verify that, as it makes a big difference to rpm.
19" seems on the low side to me, but it depends on the length/weight of your boat. For comparison, my 19' bowrider came with a 21" on a 350, and after some motor work, it revs to 5500. I'll be using a 23" this summer.

 

[Don S]

Re: Prop Pitches??

Re: Prop Pitches??

Moving to Prop forum