My wife and I are looking to live aboard. I have found the answer to most of my questions on this site, however I would like to hear what the +/- are of the Yahnmar 27HP vs the 40HP. I plan to go with an in mast furling and an Autoprop. I am interested in cruising, NOT racing this boat, although we may do some coastal travel in the future. Fuel consumption is more important than a gain of 2 Knots. I have heard the 27HP's only use 1/2 GPH, is this true? Would a 27HP be underpowered on a boat of this size(with an Autoprop)? What would the cost difference be if ordered brand new? I would like to thank anyone who answers for their time and consideration on this topic.
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My .02c
This may not help, but data is data. Use it as you see fit. My B473 has a 75hp Volvo turbo diesel. It's a really great engine with plenty of power; very quiet too. Our previous B38s5 had a Volvo 43hp, which I think was perfectly sized for that boat. I can't speak to the differences in fuel consumption, though I am very confident the differences between 27hp and 40hp are negligible. I am certain the performance difference is not. You are moving a 15,000lbs+ boat. If it were me, I'd want more HP. Sorry for the reference to Volvo. It's what we've known for 17 years. Good luck. The B373 is a beauty.
This may not help, but data is data. Use it as you see fit. My B473 has a 75hp Volvo turbo diesel. It's a really great engine with plenty of power; very quiet too. Our previous B38s5 had a Volvo 43hp, which I think was perfectly sized for that boat. I can't speak to the differences in fuel consumption, though I am very confident the differences between 27hp and 40hp are negligible. I am certain the performance difference is not. You are moving a 15,000lbs+ boat. If it were me, I'd want more HP. Sorry for the reference to Volvo. It's what we've known for 17 years. Good luck. The B373 is a beauty.
NOT TOO MUCH QUESTION
I think you have to just think thur how far your going, the differece in fuel comsumption is usually of little consequence as long as you know how much it uses and plan accordingly. I have a 37, with 40 h.p. i dont often run it hard, it kinda loafs along doing its thing at 1/2 throttle. But when its blowing like the hammers of hell and im trying to get into a pass with 4 knots of current against me, I really like being able to throttle up and throw the fuel to it. The extra power is great if you tow a dingy, or another boat, or fight big seas or need some extra oomph to get in against the current or wind. If your going cruising you probably wont be to many places where the difference in fuel consumption is a big issuse. You dont have enough to cross any big water anyway. so you have to sail. Id go for the big engine with the biggest alternator they offer. (see you already need the extra power to help with a big power robing alternator!)
I think you have to just think thur how far your going, the differece in fuel comsumption is usually of little consequence as long as you know how much it uses and plan accordingly. I have a 37, with 40 h.p. i dont often run it hard, it kinda loafs along doing its thing at 1/2 throttle. But when its blowing like the hammers of hell and im trying to get into a pass with 4 knots of current against me, I really like being able to throttle up and throw the fuel to it. The extra power is great if you tow a dingy, or another boat, or fight big seas or need some extra oomph to get in against the current or wind. If your going cruising you probably wont be to many places where the difference in fuel consumption is a big issuse. You dont have enough to cross any big water anyway. so you have to sail. Id go for the big engine with the biggest alternator they offer. (see you already need the extra power to help with a big power robing alternator!)
Hi Robbie, one half gallon per hour for a 27 HP...
Yanmar running at cruising speed seems a bit low. Assuming a cruising RPM of around 3,000 I would estimate consumption closer to a gallon per hour. Our 18HP Yanmar 2GM consumed about three quarters of a gallon at 3,000 RPM. Terry
Yanmar running at cruising speed seems a bit low. Assuming a cruising RPM of around 3,000 I would estimate consumption closer to a gallon per hour. Our 18HP Yanmar 2GM consumed about three quarters of a gallon at 3,000 RPM. Terry
Robbie, at the risk of being rude you don't seem
to understand that the rating of an engine bears only a small amount on the fuel consumption. All diesel engines are rated in terms of Grams of fuel per horse power per hour. Even if you have a 40 hp engine if the prop can only absorb 15 hp then that is all the fuel the engine will consume. You may be able to select a prop and gear ratio that will absorb 40 hp but you speed is limited by hull shape and length. My 30 foot boat requires 4 hp for 4.4 knots , 9.5 hp for 5.6 knots and 19.7 hp for 6.7 knots. My fuel consumption rate is 285 grams per hp per hour. The math isn't difficult. If speed is important then you must be prepared for the cost.
to understand that the rating of an engine bears only a small amount on the fuel consumption. All diesel engines are rated in terms of Grams of fuel per horse power per hour. Even if you have a 40 hp engine if the prop can only absorb 15 hp then that is all the fuel the engine will consume. You may be able to select a prop and gear ratio that will absorb 40 hp but you speed is limited by hull shape and length. My 30 foot boat requires 4 hp for 4.4 knots , 9.5 hp for 5.6 knots and 19.7 hp for 6.7 knots. My fuel consumption rate is 285 grams per hp per hour. The math isn't difficult. If speed is important then you must be prepared for the cost.
fuel consumtion table
...the Yanmar you refer to is rated 29 hp and is what I have in my B 343...after several hundred nautical miles I can verify the fuel consumpion table in the owners manual which is 1/2 gallon per hour at rpm of up to 2600...for what it is worth, I would go with the larger Yanmar for those times when you may need extra power for safety and security...good sailing, Bill
...the Yanmar you refer to is rated 29 hp and is what I have in my B 343...after several hundred nautical miles I can verify the fuel consumpion table in the owners manual which is 1/2 gallon per hour at rpm of up to 2600...for what it is worth, I would go with the larger Yanmar for those times when you may need extra power for safety and security...good sailing, Bill
Robbie, diesel engines like to run
at close to maximum RPM and so by design of transmission ratios and prop diameter and pitch measurements both the 27 HP engine and the 40HP engine will be operating at similar RPMs. Fuel consumption is a direct result of engine displacement and RPM. Every turn of the crankshaft will fill the combustion chambers with a mixture of fuel and air. The larger the bore and stroke of the cylinders the more fuel consumed. As most diesels by desing turn at a maximum of 3,500 to 3,800 rpms the larger horsepower in normally aspirated engines only comes as a result of increased displacement. That 40 hp engine will be larger than the 27hp and by turning at similar rpm the larger engine will use more fuel. I'm not saying the larger engine will be less fuel efficient as that would be a measure of producing horse power but I'm saying it will use more fuel. What do you get for that additional fuel? The ability to better motor against wind and current and the ability to drive a larger alternator and even a refrigeration compressor. A 27 HP engine of around 54 cubic inches of displacemnt should burn around 3/4 of a gallon an hour while the 40hp engine with around 78 cubic inches of displacement will burn around 1 1/4 GPH. Don't take this figures at face value and use the burn rates which sailors with these engines may provide. Ask a Hunter dealer about the difference in price for the engine upgrade. I myself would go with the stronger engine.
at close to maximum RPM and so by design of transmission ratios and prop diameter and pitch measurements both the 27 HP engine and the 40HP engine will be operating at similar RPMs. Fuel consumption is a direct result of engine displacement and RPM. Every turn of the crankshaft will fill the combustion chambers with a mixture of fuel and air. The larger the bore and stroke of the cylinders the more fuel consumed. As most diesels by desing turn at a maximum of 3,500 to 3,800 rpms the larger horsepower in normally aspirated engines only comes as a result of increased displacement. That 40 hp engine will be larger than the 27hp and by turning at similar rpm the larger engine will use more fuel. I'm not saying the larger engine will be less fuel efficient as that would be a measure of producing horse power but I'm saying it will use more fuel. What do you get for that additional fuel? The ability to better motor against wind and current and the ability to drive a larger alternator and even a refrigeration compressor. A 27 HP engine of around 54 cubic inches of displacemnt should burn around 3/4 of a gallon an hour while the 40hp engine with around 78 cubic inches of displacement will burn around 1 1/4 GPH. Don't take this figures at face value and use the burn rates which sailors with these engines may provide. Ask a Hunter dealer about the difference in price for the engine upgrade. I myself would go with the stronger engine.
propulsion systems
You can't just slap stuff together and expect to get good results!!!! Putting a 100 HP motor on a 5 HP prop fitted to a hull that needs 20 HP in calm conditions and then expecting it to preform in high seas and winds is clearly dumb. As ED indicated in his post, you want some reserve power for those Kodak moments. So figure out how much power is required to push the boat at hull speed in calm water and with a clean hull. This is best accomplished by going out and doing it. Just note the throttle position (0-100% of WOT) and multiply the max HP by that to get a good estimate. Now the fun begins, you have to get a new engine HP-RPM graph and find our at what RPM the new engine will be producing the required HP and then pick a transmission and prop to operate at that engine speed and speed through the water. You have to first pick a transmission and then note the gear reduction to get the new prop shaft RPM. This and hull speed (don't use the formula) will determine the pitch needed for the new prop. Figure on (let the flaming begin) 25% slippage of the prop. I use 25% slippage and not the textbook 50% due to the fact that a 50% figure is how the textbook guys factor in the power reserve. I defined the problem so we where doing the easiest least slippage end of the envelope and so adjusted the slippage downward. This site has a calculator. Note the MPH and not knots for speed.
You can't just slap stuff together and expect to get good results!!!! Putting a 100 HP motor on a 5 HP prop fitted to a hull that needs 20 HP in calm conditions and then expecting it to preform in high seas and winds is clearly dumb. As ED indicated in his post, you want some reserve power for those Kodak moments. So figure out how much power is required to push the boat at hull speed in calm water and with a clean hull. This is best accomplished by going out and doing it. Just note the throttle position (0-100% of WOT) and multiply the max HP by that to get a good estimate. Now the fun begins, you have to get a new engine HP-RPM graph and find our at what RPM the new engine will be producing the required HP and then pick a transmission and prop to operate at that engine speed and speed through the water. You have to first pick a transmission and then note the gear reduction to get the new prop shaft RPM. This and hull speed (don't use the formula) will determine the pitch needed for the new prop. Figure on (let the flaming begin) 25% slippage of the prop. I use 25% slippage and not the textbook 50% due to the fact that a 50% figure is how the textbook guys factor in the power reserve. I defined the problem so we where doing the easiest least slippage end of the envelope and so adjusted the slippage downward. This site has a calculator. Note the MPH and not knots for speed.
Owner Reviews
Did you check the owner reviews on that model, I was out on a 37.3 with 40 hp and maxprop recently and it was the owner first time out with it being brand new. So it had plenty of power but we did not motor in any ruff currents and it handle fine for a quick sail and motor up a river and out the sound with no strong currents to fight. I have the 29 yanmar on my hunter 36 and my first sail home and thru some currents and inlets it did fine but also new boat and too soon to tell how she will motor in ruff currents. I'll get to do some more motoring and sailing today and this weekend. Try the owner reviews and e-mail some owners with questions that's what I did when I was looking at the 37.3 and hunter 36. Nick
Did you check the owner reviews on that model, I was out on a 37.3 with 40 hp and maxprop recently and it was the owner first time out with it being brand new. So it had plenty of power but we did not motor in any ruff currents and it handle fine for a quick sail and motor up a river and out the sound with no strong currents to fight. I have the 29 yanmar on my hunter 36 and my first sail home and thru some currents and inlets it did fine but also new boat and too soon to tell how she will motor in ruff currents. I'll get to do some more motoring and sailing today and this weekend. Try the owner reviews and e-mail some owners with questions that's what I did when I was looking at the 37.3 and hunter 36. Nick
Yanmar
As usual, you are getting some good advice, and some bad advice. The Yanmar 27 hp is designed to cruise at 75% wot (3600) which is 2700 rpm...it will use about 1/2 gph. The rule of thumb is 1 hp for each 500 lbs of boat weight.
As usual, you are getting some good advice, and some bad advice. The Yanmar 27 hp is designed to cruise at 75% wot (3600) which is 2700 rpm...it will use about 1/2 gph. The rule of thumb is 1 hp for each 500 lbs of boat weight.
Doesn't his boat come standard with the 39HP
engine with 3 bladed prop ? This is probably most appropriate for your intended use. I've never heard anyone say they wish they had a smaller engine unless they were reducing weight to race. Fuel economy is usually not a major consideration in a sailboat, they are an economical low speed motor launch by nature. Most people do not bother with autoprops for liveaboard/cruisers either.
engine with 3 bladed prop ? This is probably most appropriate for your intended use. I've never heard anyone say they wish they had a smaller engine unless they were reducing weight to race. Fuel economy is usually not a major consideration in a sailboat, they are an economical low speed motor launch by nature. Most people do not bother with autoprops for liveaboard/cruisers either.
My experience
with a 2006 373: I have the 40hp Yanmar and burned 72 litres = 20 gallons in 30 hours of use my first season. This would mostly be slow speed in and out of the slip and short distances in channels and when becalmed. Rarely as much as an hour at cruising speed. My normal cruising is at 6.5 knots which is achieved at about 2200 rpm. I have a three blade feathering prop (Variprop) which I would recommend. The engine tops out at 3100 rpm with this prop, after I adjusted the pitch to make it finer when the boat was hauled in the fall. I like the extra stopping power and punch through wind and waves the bigger engine provides. Actual weight of the boat with tanks full, crew of four and normal equipment is about 16,500. If you want more specifics, email me (see profile.)
with a 2006 373: I have the 40hp Yanmar and burned 72 litres = 20 gallons in 30 hours of use my first season. This would mostly be slow speed in and out of the slip and short distances in channels and when becalmed. Rarely as much as an hour at cruising speed. My normal cruising is at 6.5 knots which is achieved at about 2200 rpm. I have a three blade feathering prop (Variprop) which I would recommend. The engine tops out at 3100 rpm with this prop, after I adjusted the pitch to make it finer when the boat was hauled in the fall. I like the extra stopping power and punch through wind and waves the bigger engine provides. Actual weight of the boat with tanks full, crew of four and normal equipment is about 16,500. If you want more specifics, email me (see profile.)
WOW! Thanks for all the feedback!
I did not expect sooo much feedback this quick, you guy's rock! Thank you all for your feedback. Me and the wife are gunna go for the 40HP. Man I can't wait to get my boat! Wish me luck, I'll send some e-mail once we get her. Thanks again.
I did not expect sooo much feedback this quick, you guy's rock! Thank you all for your feedback. Me and the wife are gunna go for the 40HP. Man I can't wait to get my boat! Wish me luck, I'll send some e-mail once we get her. Thanks again.
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