I would like to know if anyone has had any expierence with putting a 3 blade folding prop on an H36. I had a 3 blade fixed prop on, 15x11, and was turning 3800 RPM full throtle. I put on a Varifold 16x11 folding prop as recommended by the mfg. and could only turn 3150 RPM. The mfg. sent me new blades 16x10 but my RPM only went up to 3250 which Yanmar says is not enough and will damage the engine. I could take the 16x11 into a prop shop and have it cut down to a 15" but every moves costs. Anyone with a solution?
Folding propeller
- Thread starter robertzi
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The difference in max RPM between your original 15" and latest 16" seems too large to be attributable to only 1" in diameter so I would look for another contributory cause. You could ask for 15" blades from the prop maker but it might be that having 15" blades on the new prop may still leave you short of RPM. For info, the achilles heel of folding props is their ability to open properly when reverse is selected whilst the boat has forward speed. This is achieved by thickening the blade tips to increase their weight. The tip is the fastest moving part of the blade so really needs to be the thinnest part; so the designer has to strike a balance. If you remove the tips you may compromise your ability to stop in an emergency and also your manoeuvering in tight spaces. I had exactly the same problems on a 30' cruiser racer so I sold my folder and bought an adjustable pitch feathering type. I also have a 3 blade featherer on my H376 which is very successful.
The difference in max RPM between your original 15" and latest 16" seems too large to be attributable to only 1" in diameter so I would look for another contributory cause. You could ask for 15" blades from the prop maker but it might be that having 15" blades on the new prop may still leave you short of RPM. For info, the achilles heel of folding props is their ability to open properly when reverse is selected whilst the boat has forward speed. This is achieved by thickening the blade tips to increase their weight. The tip is the fastest moving part of the blade so really needs to be the thinnest part; so the designer has to strike a balance. If you remove the tips you may compromise your ability to stop in an emergency and also your manoeuvering in tight spaces. I had exactly the same problems on a 30' cruiser racer so I sold my folder and bought an adjustable pitch feathering type. I also have a 3 blade featherer on my H376 which is very successful.
Robert, one more thing.
Not sure what model Yanmar you're running, but 3800 RPM seems awfully high for even Yanmars. If I were you I'd check the spec sheet and determing the max horsepower 'continuous' rating, and shoot for that. Even a little less won't hurt. Reving an engine to 3800 RPM seems to me to be a parts-busting profit tool.
Not sure what model Yanmar you're running, but 3800 RPM seems awfully high for even Yanmars. If I were you I'd check the spec sheet and determing the max horsepower 'continuous' rating, and shoot for that. Even a little less won't hurt. Reving an engine to 3800 RPM seems to me to be a parts-busting profit tool.
h-36 3ym-30
My H-36 has a 3YM-30 with a top speed of 3600 rpm. The manual says it's a gm-3o. I new some was wrong the fist time I changed the oil filter.
My H-36 has a 3YM-30 with a top speed of 3600 rpm. The manual says it's a gm-3o. I new some was wrong the fist time I changed the oil filter.
h356 folding prop
we've got a 3 blade autoprop on our '02 356, and it's great. the engine is a 3gm30, max rpm 3600.max cruise on a diesel should be about 80% of max, in our case 2880rpm. I would expect your 3ym to have similar numbers. 3800 rpm seems too fast for a yanmar, your prop definitely needs to be corrected if nothing else has changed
we've got a 3 blade autoprop on our '02 356, and it's great. the engine is a 3gm30, max rpm 3600.max cruise on a diesel should be about 80% of max, in our case 2880rpm. I would expect your 3ym to have similar numbers. 3800 rpm seems too fast for a yanmar, your prop definitely needs to be corrected if nothing else has changed
Too fast too fast
Look at this quote from another website. I think you 36 boys are running to hot. Are you trying to ski behind that thing? Quote Let's cut to the chase..... If you want the engine to last past Christmas! For prolonged running, a pleasure boat engine a good operating speed is around 85% of maximum continuous rated RPM (see the engine data plate) assuming the propeller size is correct and the engine can reach maximum rpm). See this list for approximate rpm: GM - 4JH - 3/4JH2 series 2900rpm YM series Depending on WOT rpm 2600-2900rpm End quote See for yourself at this link
Look at this quote from another website. I think you 36 boys are running to hot. Are you trying to ski behind that thing? Quote Let's cut to the chase..... If you want the engine to last past Christmas! For prolonged running, a pleasure boat engine a good operating speed is around 85% of maximum continuous rated RPM (see the engine data plate) assuming the propeller size is correct and the engine can reach maximum rpm). See this list for approximate rpm: GM - 4JH - 3/4JH2 series 2900rpm YM series Depending on WOT rpm 2600-2900rpm End quote See for yourself at this link
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