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What pitch prop do I need

J

jerryh

Member
"I have a 1986 Glasstream 15ft

"I have a 1986 Glasstream 15ft with a 120hp chev engine and a alpha1. Right now I have a 17 pitch prop on it. What pitch can I increase too? Thanks, Jerry"
 
pretty sure a 13 3/4 x 21P
bu

pretty sure a 13 3/4 x 21P
but prop pitch is determined by the wide open throttle reading.eg. 42-4400 lower pitch =better hole shot. higher= better top speed
 
""Hole shot" is a term

""Hole shot" is a term used to describe how fast a boat gets onto plane from a dead stop. This is critical for skiing, tubing, etc. A good tournament or tow sport boat is one that will accelerate from zero to about 40 mph in the least amount of time. Top end speed is of secondary importance.

The lower your prop pitch, the better the hole shot; but too low a pitch and you will over rev at WOT. It's a trade off.

Also to get good hole shot, you need a prop that will "slip" enough in still water to allow the engine to quickly get well up into its best torque curve; ie about 3000+ RPM. Hole shot performance will lag if the engine is bogged by a prop with too much total blade area and/or too much pitch. This is no big deal if your water skier can hold his/her breath for a while, but mostly you want to get up onto plane as fast as possible.

Here's the link to a spreadhseet I posted that will help you choose the best prop:

http://www.marineengine.com/discus/messages/12486/Boat_Speed_Finder-79780.xls

Good luck,
Rod"
 
"Thanks, Rod. Between this and

"Thanks, Rod. Between this and my RPM thread it's all starting to come together now. Pretty fascinating stuff, really. I am amazed at how critical proper prop selection is."
 
Bill;
No problem.
The prop i

Bill;
No problem.
The prop in boat world is akin to "where the rubber meets the road" in car world.
It's all about getting the right components to be able to "hook up" effectively.
Rod
 
"Bill:

Stainless steel prop

"Bill:

Stainless steel props are less suseptible to "flexing" like aluminum under load. However, like different cars, not all SS props of the same pitch produce the same results. Case in point: I have been helping a young novice boater get his boat in top running condition. He kept telling me that he had a SS 19 pitch prop already but would try another. I sent him a brand new Michigan Wheel vented prop of the same size and pitch to try. To his delight, his boat picked up 9 more MPH and jumped out of the hole. He was so happy that he burned a tank of fuel on the water. His comment when he changed the prop; the prop you sent me was much heavier than the one I removed--cheap design?

Just get a quality prop. That doesn't mean spend $400; shop around for a quality prop. I bought the prop in Dec. 2006 for half the cost of retail from an on-line dealer that was closing out some excess stock.

Happy boating.

P.S. I spent 8 hours alone on the water fishing today starting at 6 a.m. Only caught two good bass but the breeze and sun were extremely relaxing. I can only compare the relaxation to that which I get spending an October day in a woodlot with my bow hunting whitetail deer. During deer season, I see many deer but rarely take a shot; just being there with nature is a mental high just like being on the water."
 
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