our 1995 "336" has a Yanmar 3gm diesel. does anyone know what the appropriate rpm is for cruising, and what the max is? is do not have an engine manual. on some of the literature that i read on the boat, it said that hull speed was approx. 7.2 - is only seem to get about 4.2 under ideal conditions. what do you find?
- Status
Clean hull & prop?
We have a 1987 Hunter 40 and can not reach hull speed under power. At max continuous RPM (3400) we hit 6.9 knots and our hull speed should be about 7.6. A friend with a sister ship easily reaches his hull speed. The difference is prop pitch. Hunter supplied our boat with a 17x10 (17" diameter by 10" pitch) two blade prop. A previous owner switched to a 17x8 three blade. Our friend has a 17x11 two blade on his. Hunter put a 16x10 two blade on yours. Is that what you still have? We now own, but have not yet installed a 17x10 three blade. We expect to reach hull speed with it. There is info on web for selecting prop size. There are several sites, but they may all repeat info from Michigan Propeller. (Our new MI prop cost $400.) The basic deal is with a clean hull and prop, try to get to max engine RPM. With the right prop wide open throttle should produce the max or "red line" RPM. Of course you need to find out what that is for your engine. Ours, like the h376 (see the bottom of this note) is 3600 RPM. With clean hull and clean 17x8 prop we can exceed 4000 RPM indicating we needed more pitch. In late July a couple of years ago we had enough marine growth that we could only turn 3100 RPM. Moral of the story: get hull and prop clean before experimenting. The following information is from "unofficial operators tips paper" written by the owner of a Hunter 376. The paper was designed to be a ready reference for the 3JH2E diesel engine used in the Hunter 376 and 380. Much of what is presented is also applicable to other Yanmar engines used in various Hunter sailboat models. Run the engine with a load except for 2-3 minutes warm up time at idle. 750-850 rpm normal idle; 2500-2800 sustained cruise at desired speed; 2800-3400 to maintain speed in tough wind/current/wave conditions or to reach hull speed as necessary (approaching 7.6 knots in a steady sea state with normal weight aboard). Red line is 3600 rpm +/- 50 rpm on the Hunter 376 engine tachometer. Hope this is helpful. Know it is not the whole picture. Good luck.
We have a 1987 Hunter 40 and can not reach hull speed under power. At max continuous RPM (3400) we hit 6.9 knots and our hull speed should be about 7.6. A friend with a sister ship easily reaches his hull speed. The difference is prop pitch. Hunter supplied our boat with a 17x10 (17" diameter by 10" pitch) two blade prop. A previous owner switched to a 17x8 three blade. Our friend has a 17x11 two blade on his. Hunter put a 16x10 two blade on yours. Is that what you still have? We now own, but have not yet installed a 17x10 three blade. We expect to reach hull speed with it. There is info on web for selecting prop size. There are several sites, but they may all repeat info from Michigan Propeller. (Our new MI prop cost $400.) The basic deal is with a clean hull and prop, try to get to max engine RPM. With the right prop wide open throttle should produce the max or "red line" RPM. Of course you need to find out what that is for your engine. Ours, like the h376 (see the bottom of this note) is 3600 RPM. With clean hull and clean 17x8 prop we can exceed 4000 RPM indicating we needed more pitch. In late July a couple of years ago we had enough marine growth that we could only turn 3100 RPM. Moral of the story: get hull and prop clean before experimenting. The following information is from "unofficial operators tips paper" written by the owner of a Hunter 376. The paper was designed to be a ready reference for the 3JH2E diesel engine used in the Hunter 376 and 380. Much of what is presented is also applicable to other Yanmar engines used in various Hunter sailboat models. Run the engine with a load except for 2-3 minutes warm up time at idle. 750-850 rpm normal idle; 2500-2800 sustained cruise at desired speed; 2800-3400 to maintain speed in tough wind/current/wave conditions or to reach hull speed as necessary (approaching 7.6 knots in a steady sea state with normal weight aboard). Red line is 3600 rpm +/- 50 rpm on the Hunter 376 engine tachometer. Hope this is helpful. Know it is not the whole picture. Good luck.
Most sources say
you should cruise at 80% of wide open throttle. as for the speed, also be sure your knot meter is calibrated. Many aren't, which can lead to problems like this one.
you should cruise at 80% of wide open throttle. as for the speed, also be sure your knot meter is calibrated. Many aren't, which can lead to problems like this one.
336/340 Speed...
We normally motor at 2800 RPM on our 98 340 (same hull and engine as your 336). In flat water with minimal wind and current the GPS indicated speed is about 6.2 knots. With larger waves and/or wind speed drops down to 5.2 or so. Are you reading your speed from the GPS or impeller type knotmeter? Sometimes the transducer gets fouled or perhaps the unit needs to be calibrated. If you're only getting 4.2 knots on the GPS (be sure to turn around 180 degrees and recheck to cancel out wind/current) then maybe the boats bottom or prop needs to be cleaned. Running the engine flat out at 3600 RPM might get you close to hull speed but it's not very good for the engine...
We normally motor at 2800 RPM on our 98 340 (same hull and engine as your 336). In flat water with minimal wind and current the GPS indicated speed is about 6.2 knots. With larger waves and/or wind speed drops down to 5.2 or so. Are you reading your speed from the GPS or impeller type knotmeter? Sometimes the transducer gets fouled or perhaps the unit needs to be calibrated. If you're only getting 4.2 knots on the GPS (be sure to turn around 180 degrees and recheck to cancel out wind/current) then maybe the boats bottom or prop needs to be cleaned. Running the engine flat out at 3600 RPM might get you close to hull speed but it's not very good for the engine...
Check your engine plate
On the frond of the engine with serial numbers. Yannie 3GMs used to max at 3400, newer engines at 3600, probably because of newer oils than anything else as I don't think the engine design has changed in 15 years. Then go about 80% (or about 2800 RPM), like Phil says. BTW, you should run the engine at load (i.e. 80%) frequently. It is good for them. It is bad for desiels to run continuously below load. Idling them for hours (like charterers frequently do) is terrible for them.
On the frond of the engine with serial numbers. Yannie 3GMs used to max at 3400, newer engines at 3600, probably because of newer oils than anything else as I don't think the engine design has changed in 15 years. Then go about 80% (or about 2800 RPM), like Phil says. BTW, you should run the engine at load (i.e. 80%) frequently. It is good for them. It is bad for desiels to run continuously below load. Idling them for hours (like charterers frequently do) is terrible for them.
Yanmar RPMs
Nathan, I have a 1 gm Yanmar (27 foot '82 Hunter) and the manual (publication number J020A0193)which lists specs for the 1GM, 2GM, 3GM diesel engines. In my manual the 3GM (3 cyl.) Yanmar is listed with the following ratings: Continuous rating output - 3400 rpm / 20 hp 1-hr rating output - 3600 rpm / 22.5 hp Caveat - I'm not sure if the 3GM rpms in this manual, which may have been published in 1982, would apply to your much newer engine. There is also no mention of expected hull speed only the horsepower at the listed rpms. I am not a mechanic, but I take the rpm listing continuous to mean continuously and 1-hr to mean no longer than 1 hr. Phil Herring's response (cruising at approx 80% of full throttle (3400 x .80)= 2700 - 2800 rpms) seems like good advice. Dave 'Stress Aweigh'
Nathan, I have a 1 gm Yanmar (27 foot '82 Hunter) and the manual (publication number J020A0193)which lists specs for the 1GM, 2GM, 3GM diesel engines. In my manual the 3GM (3 cyl.) Yanmar is listed with the following ratings: Continuous rating output - 3400 rpm / 20 hp 1-hr rating output - 3600 rpm / 22.5 hp Caveat - I'm not sure if the 3GM rpms in this manual, which may have been published in 1982, would apply to your much newer engine. There is also no mention of expected hull speed only the horsepower at the listed rpms. I am not a mechanic, but I take the rpm listing continuous to mean continuously and 1-hr to mean no longer than 1 hr. Phil Herring's response (cruising at approx 80% of full throttle (3400 x .80)= 2700 - 2800 rpms) seems like good advice. Dave 'Stress Aweigh'
speed
My 95 336 moves along at 6+ knots at 2800 rpm's. 3200 rpms puts me at hull speed. I like to run at 2800 because there is less harmonic shaking (rails, lifelines, etc). Also I get better fuel mileage at 2800 rpm's, about 0.6 gph. The other posts here are correct in regard to checking your speed transducer, prop pitch, and hull fouling.
My 95 336 moves along at 6+ knots at 2800 rpm's. 3200 rpms puts me at hull speed. I like to run at 2800 because there is less harmonic shaking (rails, lifelines, etc). Also I get better fuel mileage at 2800 rpm's, about 0.6 gph. The other posts here are correct in regard to checking your speed transducer, prop pitch, and hull fouling.
Hunter 336 Speed
Did you ever get your speed up? I have a 336 and it seems to go along about 4.2 as well. I posted amessage about this before I saw yours
Did you ever get your speed up? I have a 336 and it seems to go along about 4.2 as well. I posted amessage about this before I saw yours
- Status