I'm purchasing a 10' hard dinghy and would like to know what everybody recommends for the engine size. The Honda 2 HP has great reviews and only weights 27 lbs but 2 HP seems a little small. Tohatsu is coming out with a brand new 3.5 HP that only weighs 38 lbs. Getting up into the 4 to 6 HP range brings the weight up to around 55 lbs. I'm only looking to transport a maximum of 4 adults from the normal achorage/mooring to the dock and back. Thanks.
what size engine for dinghy
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It depends on you. On what you want to do and
how you want to do it with the dingy that you have or later acquire. If you like to 'camp' in distant anchorages and only come to town for supplies once a month, you will need the ability to carry cargo. And if you are a hot rodder like me, you go to extremes. My 11.5 RIB has a 25 horse Yamaha. Makes my eyes water.
how you want to do it with the dingy that you have or later acquire. If you like to 'camp' in distant anchorages and only come to town for supplies once a month, you will need the ability to carry cargo. And if you are a hot rodder like me, you go to extremes. My 11.5 RIB has a 25 horse Yamaha. Makes my eyes water.
The weight is the same for 3.3 Merc
For reasons similar to yours, I elected to purchase the 3.3 Merc. The weight is the same as the 2 HP, and it has some gearing which the 2 doesn't have. Since much of where the dingy will be used, between boat and marina, has reduced speed limits - usually around 5 mph - I went for a lighter motor.
For reasons similar to yours, I elected to purchase the 3.3 Merc. The weight is the same as the 2 HP, and it has some gearing which the 2 doesn't have. Since much of where the dingy will be used, between boat and marina, has reduced speed limits - usually around 5 mph - I went for a lighter motor.
A 10 foot boat will have a hull speed
of about four kts( a bit over 4 MPH)you would be watsing money to go past the three+ hp rating. and four mph is as fast as you can walk on land. Remember you sail, you're not in a hurry.
of about four kts( a bit over 4 MPH)you would be watsing money to go past the three+ hp rating. and four mph is as fast as you can walk on land. Remember you sail, you're not in a hurry.
neutral
to putter in harbour i agree with the 3.3 hp. i have one and it pushed my 22 foot sailboat no problem, so digny will be no problem. just ask yourself if you want just forward (start and go) or get one with neutral.
to putter in harbour i agree with the 3.3 hp. i have one and it pushed my 22 foot sailboat no problem, so digny will be no problem. just ask yourself if you want just forward (start and go) or get one with neutral.
Theoretical hull speed doesn't apply
in this case. That's only for displacement hulls. A dinghy's speed, even with its centerboard down, is not limited by the amount of water it displaces and the bow wave it creates. It is entirely capable of getting up on plane with enough motor or sail power.
in this case. That's only for displacement hulls. A dinghy's speed, even with its centerboard down, is not limited by the amount of water it displaces and the bow wave it creates. It is entirely capable of getting up on plane with enough motor or sail power.
Check the rated HP
I think you will be very disappointed 2 hp on a 10 ft dingy with 4 adults my 9ft dingy has a 4hp four stroke is heavy but check to see what the rear plate has for rated hp on the dingy,your 10 ft dingy with 4 adults should use at least 5 hp maybe 6 hp and add any extra weight and you will need more ,see what the rated hp is on dingy and go the max allowed. nick
I think you will be very disappointed 2 hp on a 10 ft dingy with 4 adults my 9ft dingy has a 4hp four stroke is heavy but check to see what the rear plate has for rated hp on the dingy,your 10 ft dingy with 4 adults should use at least 5 hp maybe 6 hp and add any extra weight and you will need more ,see what the rated hp is on dingy and go the max allowed. nick
Ross, not any hull will plane
the ones which won't will sink themselves. The little green book says that some old sailboats were thought to have been sunk this way when the wind picked up and they weren't able to reduce sail quickly enough. Joe is right on this one. I have an 18 hp on my ten foot Avon RIB. It can push the 20000 pound mother ship around pretty well if need be and that has happened to me. A 2 or 4 hp engine would not have done too well.
the ones which won't will sink themselves. The little green book says that some old sailboats were thought to have been sunk this way when the wind picked up and they weren't able to reduce sail quickly enough. Joe is right on this one. I have an 18 hp on my ten foot Avon RIB. It can push the 20000 pound mother ship around pretty well if need be and that has happened to me. A 2 or 4 hp engine would not have done too well.
Ross. the key term
is "Displacement" as in "Theoretical displacement hull speed." (BTW, this subject has been beaten to death in this forum.) If mjb's dinghy has a non-planing hull or he doesn't care about getting it up on plane then the theory could be used to determine minimum power to achieve displacemtent hull speed. If not, then the theoretical displacemnt hull speed formula would not be suitable for determining the best motor size. http://powerboat.about.com/od/maintenance/l/aa012403b.htm http://powerboat.about.com/od/hulls/a/displacement.htm http://www.johnsboat.com/calcs-web.html
is "Displacement" as in "Theoretical displacement hull speed." (BTW, this subject has been beaten to death in this forum.) If mjb's dinghy has a non-planing hull or he doesn't care about getting it up on plane then the theory could be used to determine minimum power to achieve displacemtent hull speed. If not, then the theoretical displacemnt hull speed formula would not be suitable for determining the best motor size. http://powerboat.about.com/od/maintenance/l/aa012403b.htm http://powerboat.about.com/od/hulls/a/displacement.htm http://www.johnsboat.com/calcs-web.html
Joe, I know what you're saying is true
but the practical question here concerns the engine rating for a small harbor boat. I push a 4 1/2 ton, thirty foot sail boat with less than ten hp. It takes a lot of power to lift a boat onto a plane and only a small fraction of that to make hull speed. Acceleration will be very slow with a small engine but top speed will equal hull speed until the boat can be pushed onto a plane. I advised early in this thread to check the manufacturers hp rating for this boat and not exceed it. The stress inflicted on a small boat by a large engine and excessive speed has potentially deadly consequences.
but the practical question here concerns the engine rating for a small harbor boat. I push a 4 1/2 ton, thirty foot sail boat with less than ten hp. It takes a lot of power to lift a boat onto a plane and only a small fraction of that to make hull speed. Acceleration will be very slow with a small engine but top speed will equal hull speed until the boat can be pushed onto a plane. I advised early in this thread to check the manufacturers hp rating for this boat and not exceed it. The stress inflicted on a small boat by a large engine and excessive speed has potentially deadly consequences.
Joe, I know what you're saying is true
but the practical question here concerns the engine rating for a small harbor boat. I push a 4 1/2 ton, thirty foot sail boat with less than ten hp. It takes a lot of power to lift a boat onto a plane and only a small fraction of that to make hull speed. Acceleration will be very slow with a small engine but top speed will equal hull speed until the boat can be pushed onto a plane. I advised early in this thread to check the manufacturers hp rating for this boat and not exceed it. The stress inflicted on a small boat by a large engine and excessive speed has potentially deadly consequences.
but the practical question here concerns the engine rating for a small harbor boat. I push a 4 1/2 ton, thirty foot sail boat with less than ten hp. It takes a lot of power to lift a boat onto a plane and only a small fraction of that to make hull speed. Acceleration will be very slow with a small engine but top speed will equal hull speed until the boat can be pushed onto a plane. I advised early in this thread to check the manufacturers hp rating for this boat and not exceed it. The stress inflicted on a small boat by a large engine and excessive speed has potentially deadly consequences.
3.5 hp tohatsu
I have a square stern aluminum canoe tht is 17' long. It moves OK with a little 1.2 hp motor. Several times faster than I can paddle. well I recieved a 2.2hp when we bought our sailboat. That improved the canoe's speed but not dramatically. I didn't trust the old 2.2 so bought a tohatsu 3.5 which is almost exactly the size and weight as the old mercury 2.2. Again the performance improved but not that dramatically. The original 1.2hp was used on another canoe and then on an 18' daysailer a Bucaneer. It pushed the daysailer OK in a lake. Several times we were out on the lake and the wind died. The little 1.2 didn't set any speed records but easily pushed us several miles back to the ramp. The only downside to the 1.2 is tht it is noisy. We now use it on our 8' walker bay dinghy. I like it because it only weighs 13#s and I can easily put it on the dingy. The 3.5 only weighs about 33#s but it is too much for me to handle safely while in a choppy anchorage. The 1.2 pushes the walker bay several times faster than I can row and works just fine for shuttling people a 100yds or so to and from the beach. I wouldn't want to take it much farther than a mile. Even with the 1.2 the WB* feels unstable and I usually sit on a cushion in the floor. I wouldn't want to go very fast in a 10' boat loaded with 4 people!!!! Tom
I have a square stern aluminum canoe tht is 17' long. It moves OK with a little 1.2 hp motor. Several times faster than I can paddle. well I recieved a 2.2hp when we bought our sailboat. That improved the canoe's speed but not dramatically. I didn't trust the old 2.2 so bought a tohatsu 3.5 which is almost exactly the size and weight as the old mercury 2.2. Again the performance improved but not that dramatically. The original 1.2hp was used on another canoe and then on an 18' daysailer a Bucaneer. It pushed the daysailer OK in a lake. Several times we were out on the lake and the wind died. The little 1.2 didn't set any speed records but easily pushed us several miles back to the ramp. The only downside to the 1.2 is tht it is noisy. We now use it on our 8' walker bay dinghy. I like it because it only weighs 13#s and I can easily put it on the dingy. The 3.5 only weighs about 33#s but it is too much for me to handle safely while in a choppy anchorage. The 1.2 pushes the walker bay several times faster than I can row and works just fine for shuttling people a 100yds or so to and from the beach. I wouldn't want to take it much farther than a mile. Even with the 1.2 the WB* feels unstable and I usually sit on a cushion in the floor. I wouldn't want to go very fast in a 10' boat loaded with 4 people!!!! Tom
3.5 hp tohatsu
I have a square stern aluminum canoe tht is 17' long. It moves OK with a little 1.2 hp motor. Several times faster than I can paddle. well I recieved a 2.2hp when we bought our sailboat. That improved the canoe's speed but not dramatically. I didn't trust the old 2.2 so bought a tohatsu 3.5 which is almost exactly the size and weight as the old mercury 2.2. Again the performance improved but not that dramatically. The original 1.2hp was used on another canoe and then on an 18' daysailer a Bucaneer. It pushed the daysailer OK in a lake. Several times we were out on the lake and the wind died. The little 1.2 didn't set any speed records but easily pushed us several miles back to the ramp. The only downside to the 1.2 is tht it is noisy. We now use it on our 8' walker bay dinghy. I like it because it only weighs 13#s and I can easily put it on the dingy. The 3.5 only weighs about 33#s but it is too much for me to handle safely while in a choppy anchorage. The 1.2 pushes the walker bay several times faster than I can row and works just fine for shuttling people a 100yds or so to and from the beach. I wouldn't want to take it much farther than a mile. Even with the 1.2 the WB* feels unstable and I usually sit on a cushion in the floor. I wouldn't want to go very fast in a 10' boat loaded with 4 people!!!! Tom
I have a square stern aluminum canoe tht is 17' long. It moves OK with a little 1.2 hp motor. Several times faster than I can paddle. well I recieved a 2.2hp when we bought our sailboat. That improved the canoe's speed but not dramatically. I didn't trust the old 2.2 so bought a tohatsu 3.5 which is almost exactly the size and weight as the old mercury 2.2. Again the performance improved but not that dramatically. The original 1.2hp was used on another canoe and then on an 18' daysailer a Bucaneer. It pushed the daysailer OK in a lake. Several times we were out on the lake and the wind died. The little 1.2 didn't set any speed records but easily pushed us several miles back to the ramp. The only downside to the 1.2 is tht it is noisy. We now use it on our 8' walker bay dinghy. I like it because it only weighs 13#s and I can easily put it on the dingy. The 3.5 only weighs about 33#s but it is too much for me to handle safely while in a choppy anchorage. The 1.2 pushes the walker bay several times faster than I can row and works just fine for shuttling people a 100yds or so to and from the beach. I wouldn't want to take it much farther than a mile. Even with the 1.2 the WB* feels unstable and I usually sit on a cushion in the floor. I wouldn't want to go very fast in a 10' boat loaded with 4 people!!!! Tom
Thank you Tom, you beat me too it.
I was going to add the 'noise' factor that should be considered. The smaller the engine, the harder it has to work to do the same job. That also means higher operating RPM. And smaller also mean less chance of a quiet, water cooled exhaust system. Maybe it's only me, but I find small outboards annoying. And that's just for the time it takes for them to go by. My 25hp Yamaha is so quiet that it's arrival in a anchorage goes un-noticed. It's unheard when pulling next to the mothership. My wife likes to sneak up on me all the time. Can't imagine why?
I was going to add the 'noise' factor that should be considered. The smaller the engine, the harder it has to work to do the same job. That also means higher operating RPM. And smaller also mean less chance of a quiet, water cooled exhaust system. Maybe it's only me, but I find small outboards annoying. And that's just for the time it takes for them to go by. My 25hp Yamaha is so quiet that it's arrival in a anchorage goes un-noticed. It's unheard when pulling next to the mothership. My wife likes to sneak up on me all the time. Can't imagine why?
Thank you Tom, you beat me too it.
I was going to add the 'noise' factor that should be considered. The smaller the engine, the harder it has to work to do the same job. That also means higher operating RPM. And smaller also mean less chance of a quiet, water cooled exhaust system. Maybe it's only me, but I find small outboards annoying. And that's just for the time it takes for them to go by. My 25hp Yamaha is so quiet that it's arrival in a anchorage goes un-noticed. It's unheard when pulling next to the mothership. My wife likes to sneak up on me all the time. Can't imagine why?
I was going to add the 'noise' factor that should be considered. The smaller the engine, the harder it has to work to do the same job. That also means higher operating RPM. And smaller also mean less chance of a quiet, water cooled exhaust system. Maybe it's only me, but I find small outboards annoying. And that's just for the time it takes for them to go by. My 25hp Yamaha is so quiet that it's arrival in a anchorage goes un-noticed. It's unheard when pulling next to the mothership. My wife likes to sneak up on me all the time. Can't imagine why?
Hi Fred
I had a Honda 7.5 on my last boat. It made very little noise. But it was heavy and it gave me a workout putting it on and off the sailboat(26') I can't imagine putting it on a dinghy!!! Oars are amazingly quiet!!!! I actually enjoy rowing our walker bay 8. If I didn't already own the little engine I probably would just row. My wife can't row worth a darn. She tends to go in circles!!!! She loves the little engine!!! She feels safer with the engine in we can better avoid getting pooped when a large powerboat passes.
I had a Honda 7.5 on my last boat. It made very little noise. But it was heavy and it gave me a workout putting it on and off the sailboat(26') I can't imagine putting it on a dinghy!!! Oars are amazingly quiet!!!! I actually enjoy rowing our walker bay 8. If I didn't already own the little engine I probably would just row. My wife can't row worth a darn. She tends to go in circles!!!! She loves the little engine!!! She feels safer with the engine in we can better avoid getting pooped when a large powerboat passes.
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