165 mercruiser prop

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lasso

Seaman Apprentice
Joined
Jul 9, 2012
Messages
48
I've got a 1972 18ft VIP tri-hull bowrider, with 165 I-6 Mercruiser. What would be the recommended prop for overall performance. All she's going to be used for is just cruising and pulling a tube. Probable load will be 4 to 6 people, ranging from adults to kids.

Any and all help is always appreciated.
 
F

fishrdan

Admiral
Joined
Jan 25, 2008
Messages
6,989
Re: 165 mercruiser prop

lasso said:
All she's going to be used for is just cruising and pulling a tube. Probable load will be 4 to 6 people, ranging from adults to kids.
Click to expand...

Too many variables, crusing prop could be different than a tubing prop, 6 chunky adults or 1 adult and 5 skinny kids, engine in good tune and running well, waterlogged foam and a hull with a lot of extra weight???

Check out the sticky at the top of the forum and include some accurate performance numbers for "your" boat. Without knowing how the boat is performing, with a normal load, it's a shot in the dark as to what would be the correct prop for your boat.
 
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steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: 165 mercruiser prop

Not trying to be difficult but we do need your present prop size (usually under the prop nut) and lightly loaded wot rpm and speed by gps. Also wouldn't hurt to have typical all up weight ,passengers and gear.
 
jestor68

jestor68

Commander
Joined
Jun 12, 2012
Messages
2,308
Re: 165 mercruiser prop

lasso said:
I've got a 1972 18ft VIP tri-hull bowrider, with 165 I-6 Mercruiser. What would be the recommended prop for overall performance. All she's going to be used for is just cruising and pulling a tube. Probable load will be 4 to 6 people, ranging from adults to kids.

Any and all help is always appreciated.
Click to expand...

Since your WOT rpm range is 3700-4300 rpm; you can use that as a scale to see if your motor is turning within it's proper rpm range and go from there. You want it to be at/near the top of the range with a light load, so that it will still be able to haul the heavier load when required.

If adjustment is necessary, one inch of pitch change results in about 150-200 rpm change. Reduce pitch to raise rpm; add pitch to reduce rpm. :)
 
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