I'm posting my results for anyone who has similar equipment.
2005 Mac 26M
2005 F60 4 stroke
1.85 gear ratio
Rated at 60hp @ 5500 rpm
Boat is lightly loaded for cruising and no ballast with Pam and I onboard.
(12 gallons of gas, 5 gallons of water, 70lb dinghy and 30lb motor and basic safety equipment)
Old Prop:
10-5/8" dia x12" pitch
4400 rpm and almost 16.0 mph (by gps with empty ballast)
The trouble is it wouldn't quite plane.
New Prop:
12-1/4" dia x 9" pitch
5500 rpm and 18.0mph by gps
and the boat does plane.
I'll be watching more and updating my results as the year goes on. But my conclusion is that this seems to work. The motor sounds stronger at all speeds and the top end is in the correct range. The speed was a little slower than I had hoped. It would probably go faster if I empty the boat and go alone but what would be the fun of that?
There was one peculiar thing. The new prop sings. Don't know what that means. But I have the old prop for a spare if the new one disintegrates.
2005 Yamaha F60 Propeller Conclusion
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ChrisP and Pam
- Chief Steward
- Posts: 51
- Joined: Mon May 02, 2005 9:35 pm
singing prop
Your prop sounds like a Solas with the pressure cast aluminum giving it a tighter crystal structure like a crystal glass. Does it sing at one precise RPM and no other?
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Terry
- Admiral
- Posts: 1487
- Joined: Thu Feb 19, 2004 2:35 pm
- Sailboat: MacGregor 26M
- Location: Vancouver, B.C. Canada. '03 26M - New Yamaha 70
Something doesn't sound right???
At the beginning of the season with a fresh waxed hull and very light load I can get 18-19 mph with my Honda 50 @ 5750rpm with a 2:09 gear ratio and a 4 X 11.4 X 9.5 Solas Alcup (9.5 is pitch). I would expect to hit 20mph with that extra 10HP! Where is that 70 lbs dinghy & 30 lbs motor, are you towing it? I do not have my dinghy and motor with me unless I am on an extended trip because there is no where to carry the engine other than the transom of the dinghy, therefore it has to be towed.
Perhaps you might try that test again without the dinghy, less gas & water and just for testing sake, solo.
My prop has about .8 inches less diameter than yours and maybe .5 inches more pitch but four blades, still I don't think my speed should be so close to yours. FWIW my speed drops considerably after a few weeks of marine growth and extra provisions for extended cruising, I only get that speed at the beginning of the season when I make a conscious effort to keep the boat light and hull clean.
At the beginning of the season with a fresh waxed hull and very light load I can get 18-19 mph with my Honda 50 @ 5750rpm with a 2:09 gear ratio and a 4 X 11.4 X 9.5 Solas Alcup (9.5 is pitch). I would expect to hit 20mph with that extra 10HP! Where is that 70 lbs dinghy & 30 lbs motor, are you towing it? I do not have my dinghy and motor with me unless I am on an extended trip because there is no where to carry the engine other than the transom of the dinghy, therefore it has to be towed.
Perhaps you might try that test again without the dinghy, less gas & water and just for testing sake, solo.
My prop has about .8 inches less diameter than yours and maybe .5 inches more pitch but four blades, still I don't think my speed should be so close to yours. FWIW my speed drops considerably after a few weeks of marine growth and extra provisions for extended cruising, I only get that speed at the beginning of the season when I make a conscious effort to keep the boat light and hull clean.
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Richard O'Brien
- Captain
- Posts: 653
- Joined: Fri May 14, 2004 8:20 am
- Location: Lakewood, CO. Mercury 60hp bigfoot M0427B404
Chris and Pam
I had a 2 cycle yammy 70 when I first got my boat. it had a scored piston, and has been seting in my garage for the past two years waiting for me to get the flywheel off. (saltwater frozen) It had a 14 inch diam 10 pitch prop, and even though it's a 70 i believe your high thrust could take a 14/10. I wish it hadn't smoked so much because I really liked that motor.
I had a 2 cycle yammy 70 when I first got my boat. it had a scored piston, and has been seting in my garage for the past two years waiting for me to get the flywheel off. (saltwater frozen) It had a 14 inch diam 10 pitch prop, and even though it's a 70 i believe your high thrust could take a 14/10. I wish it hadn't smoked so much because I really liked that motor.
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Frank C
Seems to me that the Powersailers, IN GENERAL, require a 14-inch prop to reach about 20 or 21 mph, and then some extra horsepower can push them up to 25+ mph. It's a big help, too, that most of the big motors use lower ratios (higher numerically ... i.e. 2.42:1 for my Suzi-60). I conclude such from personal experience, but more importantly from reading here. (My Suzuki-60 w/14-inch diameter prop just barely reaches 21 mph, clean & light.)
Just from intuition, it seems that a 12-inch diameter prop on a Macgregor is totally exploited by 50 horses. I suspect those extra 10 'Yammies' are just spinning that prop, not moving the boat.
It also seems that 11-pitch props predominate, because they provide the best merger of cruise speeds, with top speeds. Very few reports have shown improvement with a 13-pitch ... only the ETECs seem to have a torque curve that can take advantage. It's not so surprising that 2-strokes are horses of a different color. I believe there's only one boat spinning a 15-pitch, which is Billy's 4-stroke Suzuki-140.
Just from intuition, it seems that a 12-inch diameter prop on a Macgregor is totally exploited by 50 horses. I suspect those extra 10 'Yammies' are just spinning that prop, not moving the boat.
It also seems that 11-pitch props predominate, because they provide the best merger of cruise speeds, with top speeds. Very few reports have shown improvement with a 13-pitch ... only the ETECs seem to have a torque curve that can take advantage. It's not so surprising that 2-strokes are horses of a different color. I believe there's only one boat spinning a 15-pitch, which is Billy's 4-stroke Suzuki-140.