Can anyone give me advice on the correct propellor size for the Hunter 30 fitted with a YANMAR 2GM20F? I've got a 15/12 two blade on now and I am at max hull speed around 2750/2800 RPM. Giving it more power just strains the engine. Should I go down to a 14/12 or a 15/10?
- Status
- Not open for further replies.
Michigan Propeller
Check the web sight for Michigan Propeller. They have a great form, and will size the correct prop for you based on max engine RPM, hull speeds, etc. You have to do some flat water trial runs to get it right.
Check the web sight for Michigan Propeller. They have a great form, and will size the correct prop for you based on max engine RPM, hull speeds, etc. You have to do some flat water trial runs to get it right.
B
Bryan Pfaffenberger
Sounds correctly sized to me!
To avoid SERIOUS mechanical problems and shortened engine life, a marine diesel engine should be operated (under load) at 85% of its maximum RPMs, which in the case of the Yanmar GM engines means 2800-2900 RPM. Diesels hate to be babied! Don't hesitate to run your engine up to the 85% level continuously. For more information, see http://www.yanmarhelp.com/operate.htm (excellent site!!!)
To avoid SERIOUS mechanical problems and shortened engine life, a marine diesel engine should be operated (under load) at 85% of its maximum RPMs, which in the case of the Yanmar GM engines means 2800-2900 RPM. Diesels hate to be babied! Don't hesitate to run your engine up to the 85% level continuously. For more information, see http://www.yanmarhelp.com/operate.htm (excellent site!!!)
D
Doug
Bryan is probably right
Ray, you stated that max. hull speed is reached at 2750 to 2800. If you mean that you are in fact reaching hull speed at that rpm, which is the most fuel efficient speed according to the engine curves, your prop may be perfect. Attempt to go above hull speed will simply drain fuel with no significant gain in speed. If you are not reaching hull speed and cannot get your engine above 2750 to 2800, it would indicate that your prop may be too coarse. Good idea to check for leading edge damage, growth or fouling as well.
Ray, you stated that max. hull speed is reached at 2750 to 2800. If you mean that you are in fact reaching hull speed at that rpm, which is the most fuel efficient speed according to the engine curves, your prop may be perfect. Attempt to go above hull speed will simply drain fuel with no significant gain in speed. If you are not reaching hull speed and cannot get your engine above 2750 to 2800, it would indicate that your prop may be too coarse. Good idea to check for leading edge damage, growth or fouling as well.
but you should be able to reach -3400-3600
Ray: If you have the propper prop you should be able to reach 3400-3600 when you are in gear. I had a 15 x 12 on our H31 and it would not rev to 3400 rpm. We now have a 15 x 11 and are still slightly over propped (different type of prop). When determining prop pitch/diameter etc., you should consult with a Good prop shop and have them size it for you. Generally when you add a blade (i.e.: 2 blade to 3 blade you would use the same size prop with 1-2 deg. less pitch. You really do not want to take my word for it. Contact a good prop shop. They should stand behind their decision and would replace/ repair your prop if it were not the correct combination. You really do not need to worry about 'straining' a Yanmar. If you stay within the parameters that they are rated you will be fine. I believe that you can run a 2GM at 3400 rpms for an hour. The optimum RPM is in the 2500-3000 rpm range and you will find its' sweet spot somewhere in that range.
Ray: If you have the propper prop you should be able to reach 3400-3600 when you are in gear. I had a 15 x 12 on our H31 and it would not rev to 3400 rpm. We now have a 15 x 11 and are still slightly over propped (different type of prop). When determining prop pitch/diameter etc., you should consult with a Good prop shop and have them size it for you. Generally when you add a blade (i.e.: 2 blade to 3 blade you would use the same size prop with 1-2 deg. less pitch. You really do not want to take my word for it. Contact a good prop shop. They should stand behind their decision and would replace/ repair your prop if it were not the correct combination. You really do not need to worry about 'straining' a Yanmar. If you stay within the parameters that they are rated you will be fine. I believe that you can run a 2GM at 3400 rpms for an hour. The optimum RPM is in the 2500-3000 rpm range and you will find its' sweet spot somewhere in that range.
check out this site
I just ordered a new prop from this site they have a pretty comprehensive form to fill out to determine the correct prop for your boat. They recommended a campbell sailor CS3RH14x8x1 for my H-31, with a 2GM20F which seems odd but it is not a standard propeller. Check them out at the link below
I just ordered a new prop from this site they have a pretty comprehensive form to fill out to determine the correct prop for your boat. They recommended a campbell sailor CS3RH14x8x1 for my H-31, with a 2GM20F which seems odd but it is not a standard propeller. Check them out at the link below
H
Hal
prop size
My '80 Hunter 30 has a three blade 13x13 and a Yanmar 2GM20F... Full hull speed at 3400 RPM with a cruising speed of 5.8 knots at 2800 RPM. I will say that there are about 3 different gear ratios for the 2GM20F... Prop size and pitch are dependent on the shaft rpm, not the motor rpm that shows on the tachometer. My motor has a 2.62 gear ratio. You can determine the gear ratio from the tag on the case. good luck!
My '80 Hunter 30 has a three blade 13x13 and a Yanmar 2GM20F... Full hull speed at 3400 RPM with a cruising speed of 5.8 knots at 2800 RPM. I will say that there are about 3 different gear ratios for the 2GM20F... Prop size and pitch are dependent on the shaft rpm, not the motor rpm that shows on the tachometer. My motor has a 2.62 gear ratio. You can determine the gear ratio from the tag on the case. good luck!
- Status
- Not open for further replies.