I purcharsed an O'day 322 last fall and am just getting to actually start using it this summer. It has a Yanmar Diesel engine. The documentation on it indicates 2GM 18HP however on the enging itself it indicates 16HP. Anyways my question is what is the Optimun RPM that I should motor at. The manual indicates a maximun of 3400. I had it at 3000/3100RPM and after an hour or so the alarm for overheating sounds but when I cut back on the trottle and reduce the RPM's it goes out. 2200 RPM gives me just over four Knots. Is 3000/3100 RPM's to much for this boat or would there be a problem with the cooling system?
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HX
David If it's fresh water cooled, and you're overheating as described, you need to check the heat exchanger. RPMs vary since the signal to the tach comes from the alternator. Your question is usually the first one asked by new diesel owners, and soon becomes irrelevant, since you find the "sweet spot" after a few times out. Stu
David If it's fresh water cooled, and you're overheating as described, you need to check the heat exchanger. RPMs vary since the signal to the tach comes from the alternator. Your question is usually the first one asked by new diesel owners, and soon becomes irrelevant, since you find the "sweet spot" after a few times out. Stu
Yanmar
Yanmar has some very good forums: http://forums.torresen.com/sailing/ and: http://www.freeboards.net/?mforum=yanmarhelp
Yanmar has some very good forums: http://forums.torresen.com/sailing/ and: http://www.freeboards.net/?mforum=yanmarhelp
Stu, He's driving a Yanmar.
The tach signal is from a sensor atop the flywheel. It detects the teeth as they pass. (hall effect)
The tach signal is from a sensor atop the flywheel. It detects the teeth as they pass. (hall effect)
Depends on your prop too...
a three-bladed prop needs less rpm than a two-bladed to get the same speed. We use 2800 rpm (Yamnar 3gm30F) as our max cruise with a three bladed prop, and find that anything higher does not significantly increase speed and therefore unnecessarily increases fuel flow. Al
a three-bladed prop needs less rpm than a two-bladed to get the same speed. We use 2800 rpm (Yamnar 3gm30F) as our max cruise with a three bladed prop, and find that anything higher does not significantly increase speed and therefore unnecessarily increases fuel flow. Al
Might check the impellor if you have not changed,
this may have been the first time it's run that hard in awhile and that was all it could take. Are you getting enough flow thru raw water system out the exhaust ?
this may have been the first time it's run that hard in awhile and that was all it could take. Are you getting enough flow thru raw water system out the exhaust ?
Diesel Engines Overheating
Haven't as yet checked the impeller but there appears to be lots of water comming out the exhaust. Thanks for the advice.
Haven't as yet checked the impeller but there appears to be lots of water comming out the exhaust. Thanks for the advice.
Same engine
David, I have a "new to me" O'Day 302 with the same engine. This is my first time with a diesel. In order to get my boat home on time, I had to motor most of the way. One of the days lasted nineteen hours. We motored at 3,000 rpm with a boat speed of six knots. The engine seemed to do fine with no alarms. If it was me, I would have someone check the engine over. Having 32 feet of boat with no wind and no engine will ruin your day.
David, I have a "new to me" O'Day 302 with the same engine. This is my first time with a diesel. In order to get my boat home on time, I had to motor most of the way. One of the days lasted nineteen hours. We motored at 3,000 rpm with a boat speed of six knots. The engine seemed to do fine with no alarms. If it was me, I would have someone check the engine over. Having 32 feet of boat with no wind and no engine will ruin your day.
My Universail Motor Manual says
its a MX 25 max RPM 3000-3200 and it indicates crusing RPM of 2500-2600. at 2500 RPM it pushes my Catalina 310 at 5 to 6 knots. THe motor won;t really push you any faster than hull speed, for crusing at lenght under power I would not go over 2600 RPM
its a MX 25 max RPM 3000-3200 and it indicates crusing RPM of 2500-2600. at 2500 RPM it pushes my Catalina 310 at 5 to 6 knots. THe motor won;t really push you any faster than hull speed, for crusing at lenght under power I would not go over 2600 RPM
Same problem
You don't indicate whether your 2GM is freshwater cooled or not. When I bought a Freedom 30 with a 2GM20F, it overheated on the second day out. Don't know why and it did not happen again. The 18 HP listed is at the engine max rpm of 3600, The 16 HP is at the max sustained rpm of 3400. With target rpm of 80% of max, I'd shoot for 2800, but it should not overheat at 3100. If your engine is freshwater cooled, try cleaning out the heat exchanger with vinegar or a commercial solution. Also, make sure that the tension on the belt that runs the seawater pump has the proper tension. It could be slipping as you go faster, and thus not pump enough water.
You don't indicate whether your 2GM is freshwater cooled or not. When I bought a Freedom 30 with a 2GM20F, it overheated on the second day out. Don't know why and it did not happen again. The 18 HP listed is at the engine max rpm of 3600, The 16 HP is at the max sustained rpm of 3400. With target rpm of 80% of max, I'd shoot for 2800, but it should not overheat at 3100. If your engine is freshwater cooled, try cleaning out the heat exchanger with vinegar or a commercial solution. Also, make sure that the tension on the belt that runs the seawater pump has the proper tension. It could be slipping as you go faster, and thus not pump enough water.
This may help
If 3400 rpm is max you were running at about 88-91% of maximum. You likely have some blockage as other posts have suggested. Also note that Yanmar tachs generally read about 100 rpm too fast at max rpm so an indicated 3400 is more like 3300.. or so... these things are not exact like on gasoline engines. I would also suggest that running that fast for extended periods is probably pushing things a bit. The site below indicates a cruising rpm of 80% of maximum provided your prop will actually allow you to reach max rpm. If the engine cannot reach max rpm you are "over-propped" ie. too much pitch and or diameter. You don't say if you have a two or three blade prop or if it is fixed or folding. I know some fixed props can be re-pitched but have no idea about folding props. I have no idea if this helps but for comparision purposes our Crown 34, fin keel, disp. 12,000 lbs with all of our junk on board, does about 5 kts thru the water @ 2000-2100 rpm as read on a Yanmar tach. We run a 14 X 8, two blade Campbell Sailor Prop. Was your speed measured with a knotmeter or GPS?
If 3400 rpm is max you were running at about 88-91% of maximum. You likely have some blockage as other posts have suggested. Also note that Yanmar tachs generally read about 100 rpm too fast at max rpm so an indicated 3400 is more like 3300.. or so... these things are not exact like on gasoline engines. I would also suggest that running that fast for extended periods is probably pushing things a bit. The site below indicates a cruising rpm of 80% of maximum provided your prop will actually allow you to reach max rpm. If the engine cannot reach max rpm you are "over-propped" ie. too much pitch and or diameter. You don't say if you have a two or three blade prop or if it is fixed or folding. I know some fixed props can be re-pitched but have no idea about folding props. I have no idea if this helps but for comparision purposes our Crown 34, fin keel, disp. 12,000 lbs with all of our junk on board, does about 5 kts thru the water @ 2000-2100 rpm as read on a Yanmar tach. We run a 14 X 8, two blade Campbell Sailor Prop. Was your speed measured with a knotmeter or GPS?
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