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Correct Prop for OMC Engine

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bully515

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"Hi, just wandered if anyone c

"Hi, just wandered if anyone could help.. I've got a 1989 Sunbird Corsica with a 5.0L OMC inboard but I don't know the correct type of prop I should be running ??"
 
"Prop type and size depends on

"Prop type and size depends on what what you want to do with the boat. As a baseline, tell us what prop you have now and what your WOT (wide open throttle) RPMs are. Is the prop aluminum or SS? What diameter and pitch? (should be stamped on the prop) 3 blade or 4?"
 
"Wow thanks for the quick resp

"Wow thanks for the quick response, I'm new to all this forum stuff.. well we use the boat for wakeboarding built our own pole.. I'll have to look at the weekend as we bought the boat from someone but it didn't cum with any info.. I know it's currently got a 3 blade prop but also know this was added just before we bought it.. think the guy got it cheap and just threw it on.."
 
the correct prop is the prop t

the correct prop is the prop that puts your OMC 5L engine's rpm at wide open throttle between 4200 and 4600 rpm.
Any prop that doesn't acheive that can ruin your engine.
 
"ok, I've spent the whole

"ok, I've spent the whole day taking the leg off my boat.. In answer to some of the questions about the prop.. its got a 4 blade, SS & diameter 3 inches on it at the mo.. not sure what the pitch is as it doesn't have any info on it.. can someone tell me what the correct pitch should be ?"
 
The diameter is measured at th

The diameter is measured at the tip of the blades so it's hopefully a little bigger than 3". Only way to know if it's right for your boat is like Hystat said. You need need to run it and see what your WOT RPMs are. Should be in the 4200-4600 range. Above or below this range is not good for your engine.
 
ok thanks.. so there's no

ok thanks.. so there's no standard prop pitch or type that goes with that engine/leg.. it just depends what you want to do with the boat then get the appropriate prop that suits that engine/leg.. it's also a 15 spline shaft ??
 
"it has more to do with the we

"it has more to do with the weight of the boat, the efficiency of the hull, and the altitude of the body of water .
A 5.0L cobra in a 16' light weight boat might need a 25P to be in the 4200-4600 range wot and would probably be going 60mph
Same engine/drive in a 26' cabin cruiser might need a 13P to be in that range and might be going 25mph.

But both are using the full 230HP."
 
"Thats exactly right. There a

"Thats exactly right. There are many factors like typical boat load (people and gear), are you using mainly for skiing/tubing or just cruising? Things like that....
Four blades are good for towing, low speed planing, and good mid-range power. Three blades usually offer better top end speed. You need to do some testing to see where you are. Be sure you test with what will be a typical load-it will make a difference. you'll want to try to be towards the upper end of the range to get all the power you can"
 
"excellent.. jsut the imformat

"excellent.. jsut the imformation I was looking for.. we use the boat for wakeboarding, maybe have 4-5 people on board with some gear. and usually chug along at about 20mph. that is with the current prop of course.. not interested in tearing around just want whats best for the engine whilst wakeboarding.. initial burst to get skier up and onto plain then back off to a comfortable cruising speed..
thanks"
 
"first of all, i am in no way

"first of all, i am in no way a boat expert. please keep that in mind. just thought you might be interested in this. could be a starting point. i ordered a prop yesterday from comprop. they have a chart for the type of prop they recommend for their brand of props. it doesn't take into consideration anything except the engine year, size, and horsepower. maybe not very accurate, but also maybe worth a look. here is a link to the page:

http://www.comprop.com/omc.html

good luck!"
 
"Another guy who re-built my p

"Another guy who re-built my prop, and re-pitched it is JP Marine in Hagersville, Ontario.Mines an ancient OMC Drive ; on the Kaiser 225. Sorry for the plug, but the work he did was outstanding.Went from a 16 pitch to an 18, and I had the pleasure of operating the 20 ft.boat at the 16 pitch lvl. I noticed the change immediately. Top end at 4000 was great. Never pushed it any harder..yet.
Smart Tabs are next."
 
"excellent, thanks to all for

"excellent, thanks to all for the info on this.. the links are great. just got to get my stern drive back on now to test it all."
 
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