At 2800 rpm, and all things considered, what is the average cruising speed I should expect from my 29.5? Thank you, Jane
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Speed
Speed is clearly not a virtue of this design in my experience - under power you would be hrdpressed to reach theoretical hullspeed (which I believe is only six knots to begin with), unless you were running with a strong current. I thought of switching to a three blade prop to try to improve cruising speed - then again the added drag would hamper what the boat is supposed to do which is of course to sail... Even under sail with a good steady wind and good trim I have not experienced better than maybe 6.4 over the ground and this is running with the current. It's a nice comfortable weekend cruiser, but it is NOT a performance boat by any means - doesn't sail well with the wind and is very prone to weather helm and needs to be reefed early and frequently in any kind of stiff breeze or gusty conditions or it cannot be handled. In a good wind however, reefing does not seem to adversely affect the speed or performance. If your in a hurry, then this is not the boat for you, but then again if your in a hurry, sailing is not the sport for you either. The beauty of sailing is purely sailing, not when you get there or even where you go...
Speed is clearly not a virtue of this design in my experience - under power you would be hrdpressed to reach theoretical hullspeed (which I believe is only six knots to begin with), unless you were running with a strong current. I thought of switching to a three blade prop to try to improve cruising speed - then again the added drag would hamper what the boat is supposed to do which is of course to sail... Even under sail with a good steady wind and good trim I have not experienced better than maybe 6.4 over the ground and this is running with the current. It's a nice comfortable weekend cruiser, but it is NOT a performance boat by any means - doesn't sail well with the wind and is very prone to weather helm and needs to be reefed early and frequently in any kind of stiff breeze or gusty conditions or it cannot be handled. In a good wind however, reefing does not seem to adversely affect the speed or performance. If your in a hurry, then this is not the boat for you, but then again if your in a hurry, sailing is not the sport for you either. The beauty of sailing is purely sailing, not when you get there or even where you go...
Broooooom, Brooooom
Jane, first off I sail my 29.5 on a wide spot on the Mississippi River known as Lake Pepin. The river is 1-2 miles wide for around 20 miles here. Normal current is maybe 1 knot. Current not real noticeable. I am still running the factory basic 2 blade fixed prop. I rarely if at all ever take my Yanmar over 2500 rpms, maybe 2600. I motor between 5.2 and 5.6 with a cold beer in my hand and the stereo singing to me. I have heard stories of the Yanmar overheating with maximum rpms and I figure I am within a half knot or therabouts of hull speed and am satisfied.
Jane, first off I sail my 29.5 on a wide spot on the Mississippi River known as Lake Pepin. The river is 1-2 miles wide for around 20 miles here. Normal current is maybe 1 knot. Current not real noticeable. I am still running the factory basic 2 blade fixed prop. I rarely if at all ever take my Yanmar over 2500 rpms, maybe 2600. I motor between 5.2 and 5.6 with a cold beer in my hand and the stereo singing to me. I have heard stories of the Yanmar overheating with maximum rpms and I figure I am within a half knot or therabouts of hull speed and am satisfied.
Gary of MN.
Gary: I think that you are correct about running the engine at MAX rpms. Yes they will and do overheat. IF you are properly propped your engine should run fine at 70-80% of the max rating. For the 2GM and 3GM engine (rated at 3600) this equates to 2520-2880 rpms. You are in exactly the correct range. The other thing you will find if you can rev your engine higher to will probably just blow black smoke (tooo much fuel). The governor is delivering more fuel than the engine can burn. So I agree 2600 and a cool one is just about right.
Gary: I think that you are correct about running the engine at MAX rpms. Yes they will and do overheat. IF you are properly propped your engine should run fine at 70-80% of the max rating. For the 2GM and 3GM engine (rated at 3600) this equates to 2520-2880 rpms. You are in exactly the correct range. The other thing you will find if you can rev your engine higher to will probably just blow black smoke (tooo much fuel). The governor is delivering more fuel than the engine can burn. So I agree 2600 and a cool one is just about right.
How come ?
What's this business with the overheating... I experienced the same, but Yanmar mechanic says that engine should be capable of running at 3300RPM's all day long without overheating ?? 2600RPM is fine in no current and calm seas, but let me tell you, if you're out in the ocean and it gets rough 2600 RPM will leave you standing still - I had a couple panic attacks last summer when way out in Long Island sound and it started to get snotty - I was affraid to take the engine up past 2600 because it had been overheating in the 2800 range earlier - letting out headsail was the only way I got her moving and cutting the chop... Can anyone quantify or explain this seemingly common problem ??
What's this business with the overheating... I experienced the same, but Yanmar mechanic says that engine should be capable of running at 3300RPM's all day long without overheating ?? 2600RPM is fine in no current and calm seas, but let me tell you, if you're out in the ocean and it gets rough 2600 RPM will leave you standing still - I had a couple panic attacks last summer when way out in Long Island sound and it started to get snotty - I was affraid to take the engine up past 2600 because it had been overheating in the 2800 range earlier - letting out headsail was the only way I got her moving and cutting the chop... Can anyone quantify or explain this seemingly common problem ??
Fast Hot Yanmar....
Clay and Jane---from experience I suggest you check for constriction in the exhaust elbow. This is not in order of priority. First would be belt condition and tension. Second the impeller. Third the front of the heat exchanger. Fourth, the exchanger passages. Fifth, the hoses. Sixth the exhaust elbow. Seventh, the antifreeze mixture. Eigth, the pressure cap. But--from a lot of experience--have someone check the elbow. Rick D.
Clay and Jane---from experience I suggest you check for constriction in the exhaust elbow. This is not in order of priority. First would be belt condition and tension. Second the impeller. Third the front of the heat exchanger. Fourth, the exchanger passages. Fifth, the hoses. Sixth the exhaust elbow. Seventh, the antifreeze mixture. Eigth, the pressure cap. But--from a lot of experience--have someone check the elbow. Rick D.
Rite on Rick
Clay: Rick is correct. You need to check these items. Also you need to realize that a prop is like the rear end gears in your car. If the gears are 3:20 you can go 120 mph if you have 4:10 gears you will only be able to go 105 mph or what ever based on the redline of the engine. The prop plays essentially the same roll. If you engine will turn at least 3600 rpms in gear at wide open throttle then you should be able to run at 3200-3400 without overheating. If you cannot get that many RPM;s you are overpropped. My experience with my H'31 is that I have a 15x10 prop on the 2gm20f and it should be 15x9. Every 1 inch of pitch is going to give you about 200-250 rpms higher/lower. Check out the stuff that Rick mentioned, if that is ALL ok then check out your RPM range. If you cannot turn the max rpms then look at having your prop repitched.
Clay: Rick is correct. You need to check these items. Also you need to realize that a prop is like the rear end gears in your car. If the gears are 3:20 you can go 120 mph if you have 4:10 gears you will only be able to go 105 mph or what ever based on the redline of the engine. The prop plays essentially the same roll. If you engine will turn at least 3600 rpms in gear at wide open throttle then you should be able to run at 3200-3400 without overheating. If you cannot get that many RPM;s you are overpropped. My experience with my H'31 is that I have a 15x10 prop on the 2gm20f and it should be 15x9. Every 1 inch of pitch is going to give you about 200-250 rpms higher/lower. Check out the stuff that Rick mentioned, if that is ALL ok then check out your RPM range. If you cannot turn the max rpms then look at having your prop repitched.
Check your bottom
No, not by bending over, but by hauling. I went from 4.5 to 6.6 knots at 2800, just by having half the Chesapeake's population of barnacles removed from the prop, shaft, et al. It also ended the overheating problem.
No, not by bending over, but by hauling. I went from 4.5 to 6.6 knots at 2800, just by having half the Chesapeake's population of barnacles removed from the prop, shaft, et al. It also ended the overheating problem.
Cruising Speed--Thanks!
Thanks all for your replies, I was wanting to verify that my boat was performing normal. I'm not having any problems with overheating. I can cruise all day at 2800rpm. If I go much higher than that, I overheat in about 30 minutes ( I've tried it). I was cruising at about 5.2 knots last year. I have not had my bottom cleaned yet this year and have lost about a knot in cruising speed.
Thanks all for your replies, I was wanting to verify that my boat was performing normal. I'm not having any problems with overheating. I can cruise all day at 2800rpm. If I go much higher than that, I overheat in about 30 minutes ( I've tried it). I was cruising at about 5.2 knots last year. I have not had my bottom cleaned yet this year and have lost about a knot in cruising speed.
overheatin'
All the response have been very thoughtful. One that wasn't mentioned which might have consideration is- how hot is the ambiant air in your engine box? Hot air is thin air and that could be starving the engine burn - hence the black smoke. I have the 2GMF (no 20) and need the 2700-to-3000 rpm in a blow in Barnegatt Bay, NJ. just to keep moving. I usually pull the cushions back in the aft qtr-berth and pull back the aft engine access panel just to air things some. So far no over heating- just make sure the strainer isn't gummed up with eel grass. Also you should pull out the heat exchanger and flush it out - Lysol Direct is good ...and so are pipecleaners. Jim McCue
All the response have been very thoughtful. One that wasn't mentioned which might have consideration is- how hot is the ambiant air in your engine box? Hot air is thin air and that could be starving the engine burn - hence the black smoke. I have the 2GMF (no 20) and need the 2700-to-3000 rpm in a blow in Barnegatt Bay, NJ. just to keep moving. I usually pull the cushions back in the aft qtr-berth and pull back the aft engine access panel just to air things some. So far no over heating- just make sure the strainer isn't gummed up with eel grass. Also you should pull out the heat exchanger and flush it out - Lysol Direct is good ...and so are pipecleaners. Jim McCue
3200 rpm's
2gm I have always run my 31 at 3200 rpm when traveling never had any problems. That engines just seems to love to run there all day. I have a folding prop Martec I think 15 x 10 great combination. Oh speed at 3200 about 6.0
2gm I have always run my 31 at 3200 rpm when traveling never had any problems. That engines just seems to love to run there all day. I have a folding prop Martec I think 15 x 10 great combination. Oh speed at 3200 about 6.0
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