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Old 02-19-2013, 09:17 PM   #21
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Brooksie,

You say ... "diamater should be 32" and 28" pitch".

That would be like your boat w a 500hp engine and a 60" prop.

You can't prop Breadbasket for the engine because she can only use a small fraction of her power. Breadbasket needs to be propped to her hull. No need for more than 20" in diameter as long as enough pitch can be had to propel the boat easily at hull speed and a bit more (7 knots max). Probably will need over 20" dia to have a prop that will advance through the water at about 8 or 9 knots ... with the proper amount of slip and enough thrust to push the boat (15 to 20hp).
Agree... If 40 or 50 hp were used, there would be no need of that diameter to absorb the power and 20 or 22" would be enough. So if the engine were derated to the necessary power + reserve he could run the numbers and get the proper wheel assuming he is willing to change transmissions. As it stands now, if that smaller wheel were adopted, the engine could overspeed so needs an unnessarily large and iinefficient (friction) prop. That 50 hp will be developed at less than 1/2 current rpm so pehaps 1.5 or 2:1 transmission would be required.
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Old 02-20-2013, 07:06 AM   #22
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"For you size boat it seems to be over powered with a Lehman 120 and a 3.9 to 1 reduction.'

The boat was outfitted as a work boat to tow a trawl.

This a very different power /thrust requirement than a yacht running free.
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Old 02-20-2013, 10:19 AM   #23
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Brooksie,

There's not only no need to "absorb" the power it would be very unsafe to attempt it. JP's locked into that engine and gear for mow so the prop should be chosen to push the boat and "ratings" don't even apply. And the engine WOULD not could overspeed w pretty much whatever prop was used. So just enough prop to move the boat should be the "correct" prop. A 15" prop would be fine but w the 4-1 gear it's prop tips may/probably would'nt advance far enough in the water to push the boat power or no power. So an in-between prop of 20 to 24" may do the job.


Do you have the Grey engine in your W36?
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Old 02-20-2013, 11:42 AM   #24
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Brooksie,

Do you have the Grey engine in your W36?
Yes still the original '62 engine. 50hp @ 2000 continuous SHP
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Old 02-20-2013, 07:13 PM   #25
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Brooksie,
Good. That's one thing Willard got right on quite a few boats (yours and mine) and that is power loading. Not many trawlers can say that. But numerous Willards are over powered also. I would never have run Willy any differently if I had 5 or 6 less horsepower if you exclude running at WOT now and then to insure all is well. However the speed attained at WOT would be slightly less. Mitsubishi has a destroked version of the engine I have w 5 less horsepower and I'm sure I'd be 100% fine w that.

I absolutely love the W36 hull but don't like the visibility from the lower helm over the bow. If it weren't for that I'd have a 36 as well.
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Old 02-21-2013, 01:01 AM   #26
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I absolutely love the W36 hull but don't like the visibility from the lower helm over the bow. If it weren't for that I'd have a 36 as well.
You are correct about lower helm visibility, it is bad. I raised my helm seat to the max to suit me when I remodeled and it helped some.
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Old 02-21-2013, 09:06 AM   #27
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Brooksie,
By saying this "As it stands now, if that smaller wheel were adopted, the engine could overspeed so needs an unnessarily large and iinefficient (friction) prop." .... now I think I understand. You're thinking the prop would function as a speed limiter and it may depending on dimensional specifics but if the FI governor is set right that should be handled by same. Would be also good to install a throttle stop to avoid falling on the throttle lever and having some sort of accident from the sudden application of extremely excessive thrust.

I wish you were in the NW. I'd love to see your boat. Would like to see you and your W36 at the PNW Rendezvous coming up soon.
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Old 02-21-2013, 10:27 AM   #28
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Brooksie,
By saying this "As it stands now, if that smaller wheel were adopted, the engine could overspeed so needs an unnessarily large and iinefficient (friction) prop." .... now I think I understand. You're thinking the prop would function as a speed limiter and it may depending on dimensional specifics but if the FI governor is set right that should be handled by same. Would be also good to install a throttle stop to avoid falling on the throttle lever and having some sort of accident from the sudden application of extremely excessive thrust.

I wish you were in the NW. I'd love to see your boat. Would like to see you and your W36 at the PNW Rendezvous coming up soon.
Yes, was saying just turn the govonor down to the rpm at which 50hp is available; then run the numbers. Trouble is, with the 4:1 trans, it would, I think, come up with an even larger prop as ideal because you would have only 300 SRPM.
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