OMC Proper propeller sizing.

[CCrew]

Trying to come up with the best "all purpose" prop diameter and pitch for a newly acquired boat.. Thanks in advance for any responses. <br /><br />Motor's a 5.7 litre, although the boat's originally a 5.0 litre, so the outdrive is a 21:17 upper with a 13:26 lower ratio. According to OMC, Overall ratio is 1.50 engine revolutions to one prop revolution. <br /><br />Boat came with a 14x17 SS prop, and has about 15-20% more throttle left in it at 4600rpm redline. Haven't had it out without the wife, so don't know top speed, but it's well in excess of 40mph by GPS with room to go. Drag raced a Grady White with twin 225's on it by necessity, and was spanking him bad before the wife started complaining <br /><br />It's a 19' Deep V. <br /><br />Trying to come up with a good "all purpose" prop that'll pull hard out of the hole, yet still allow a pretty good match to RPM at WOT. Any help greatly appreciated!<br /><br />Roger

 

[chris in va]

Re: OMC Proper propeller sizing.

I'll suggest a 21p stainless. Today I finally caved in and bought one for my 19' bowrider, 302 SX. The fastest I had been able to go with other props was 38-39, but today my hat nearly flew off my head at 50! Great hole shot too, suprisingly...even running one inch longer.<br /><br />I wasted so much money on aluminum and composite props this past year.

 

[Boomyal]

Re: OMC Proper propeller sizing.

I also have a 19'+ deep vee w/ a 1:50 OMC 800 oudrive. I'm still running the 302. My boat originally came with a 15" prop and I'm currently running a cupped Michigan Wheel 15 x 17. That seems a perfect match for WOT rpm at between 4300 and 4500 depending on the load. If I had a 351W in that same boat I'd poke the pistons out the top with that prop. Assuming your in a similar situation I'd try a 15 x 21 for an all around prop. You probably don't have any trouble pulling up a skier or two with that 351.

 

[Doug Durako]

Re: OMC Proper propeller sizing.

You are running stainless now so you are seeing all the advantages of SS over aluminum. I would try to borrow a SS prop of same diameter at a 19 pitch---that should drop you 400 rpm at Wide open throttle and get you close to maximum performance.<br />Try before you buy, then search ebay for one with the same specs. A new, high quality, SS prop is going to run you close to $500 from a dealer or marina. If you are patient, you can cut that cost in half.

 

[merc 140 pontoon]

Re: OMC Proper propeller sizing.

I don't know about OMC, but Merc has a prop-sizing program on their website.<br /><br />Also, "Hit with aluminum, buy new prop; hit with SS, buy new gears."