I have an opportunity to buy a professionally re-built Yanmar 3GM30F 27hp to replace a 2GM 13 hp raw water cooled Yanmar on a 1982 Hunter 30. Has anyone done this? What modifications were needed to the shaft, alignment, etc? Is there even enough room in the engine compartment? Is it actually too much power and weight for this boat?
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2GM replacement
Why are do you want to replace you engine. Are you having a problem with it? If it is just a matter of going faster, remember, you can only go as fast as hull speed will allow you to go. After all, it is a sailboat.
Why are do you want to replace you engine. Are you having a problem with it? If it is just a matter of going faster, remember, you can only go as fast as hull speed will allow you to go. After all, it is a sailboat.
Why replace?
The original Yanmar 2GM is rusted. Does not run. It will need a complete re-build. It is out of the boat, now. I have a 1984 2GM as a replacement. We fired it up in the garage and it seems to run well. Since the 3GM F is available, I am wondering if it is worth using it. My thinking is that it will have more thrust in heavy weather, plus it is fresh water cooled. I can add a hot water heater. The down side is that it costs more and I'm not sure if it will be that much better than a 2GM. I have not had the boat in the water, yet. We will be sailing the Chesapeake Bay. What are your opinions on the Yanmar 2GM 13 hp motor? Is is strong enough? I have heard various opinions. I've heard that it has a lot of vibration and the 3 cylinder motor is much smoother.
The original Yanmar 2GM is rusted. Does not run. It will need a complete re-build. It is out of the boat, now. I have a 1984 2GM as a replacement. We fired it up in the garage and it seems to run well. Since the 3GM F is available, I am wondering if it is worth using it. My thinking is that it will have more thrust in heavy weather, plus it is fresh water cooled. I can add a hot water heater. The down side is that it costs more and I'm not sure if it will be that much better than a 2GM. I have not had the boat in the water, yet. We will be sailing the Chesapeake Bay. What are your opinions on the Yanmar 2GM 13 hp motor? Is is strong enough? I have heard various opinions. I've heard that it has a lot of vibration and the 3 cylinder motor is much smoother.
2GM or 3GMF
I have a 2GMF on my Hunter 31. It will just about push the boat at hull speed under good conditions. Having a fresh water cooled engine is a big advantage. The extra power that you'll get from the 3GMF is an advantage. Unlike a 2 cycle outboard, you want to run your diesel at about 80% power. You will find your hull speed by the sound of the engine. Listen for the smooth spot. The people that complain about engine vibration on their 2GM's are probably pushing them too hard. If the mounts are different, you are going to have to do some glass work. If you can work it out, I would go with the 3GMF. You will have the extra power available to you plus you will have a fresh water cooled engine. Both are big advantages.
I have a 2GMF on my Hunter 31. It will just about push the boat at hull speed under good conditions. Having a fresh water cooled engine is a big advantage. The extra power that you'll get from the 3GMF is an advantage. Unlike a 2 cycle outboard, you want to run your diesel at about 80% power. You will find your hull speed by the sound of the engine. Listen for the smooth spot. The people that complain about engine vibration on their 2GM's are probably pushing them too hard. If the mounts are different, you are going to have to do some glass work. If you can work it out, I would go with the 3GMF. You will have the extra power available to you plus you will have a fresh water cooled engine. Both are big advantages.
lots of other conciderations
look at fuel capicity, 3 gms burn conciderably more fuel. you could also fresh water cool the new 2 gm you have. how long did the old one last? will you have the boat long enough to offset the costs. You will probably need to increase shaft size. shorten the shaft change the strutt to accomodate the larger shaft and you may not have enough clearance for the new larger prop you will need. you may also have to increase exaust size and muffler and maybe a thru hull. get all the scoop before you muve up. The new motor will get you maybe another knot. Humm-- how far do you motor. how big a rush are you in. How much are you willing to pay to get that knot. Boat speed is 1.3 x the square root of the waterline length. calculate that and compare it to what you have in the old engine to help with your decision. And the 3 gm is a lot bigger. do you have the room? what willit do to access of starter and other accesories you may need to change down the road. just some stuff to think thru.
look at fuel capicity, 3 gms burn conciderably more fuel. you could also fresh water cool the new 2 gm you have. how long did the old one last? will you have the boat long enough to offset the costs. You will probably need to increase shaft size. shorten the shaft change the strutt to accomodate the larger shaft and you may not have enough clearance for the new larger prop you will need. you may also have to increase exaust size and muffler and maybe a thru hull. get all the scoop before you muve up. The new motor will get you maybe another knot. Humm-- how far do you motor. how big a rush are you in. How much are you willing to pay to get that knot. Boat speed is 1.3 x the square root of the waterline length. calculate that and compare it to what you have in the old engine to help with your decision. And the 3 gm is a lot bigger. do you have the room? what willit do to access of starter and other accesories you may need to change down the road. just some stuff to think thru.
same basic engine.
The 2gm and 3gm are the same basic engines. My first concern would be the overall length. While not much longer it may be a problem. I'd agree that you may not be happy with the additional fuel consumption and not much difference in overall speed. If you have a good prop the 2gm should do quite well on one of these boats.
The 2gm and 3gm are the same basic engines. My first concern would be the overall length. While not much longer it may be a problem. I'd agree that you may not be happy with the additional fuel consumption and not much difference in overall speed. If you have a good prop the 2gm should do quite well on one of these boats.
2GM 20F-18
I have a 2001 2GM20F fresh water cooled 18 horse power and it has plenty power for my 290 and uses very little fuel,so if the 3GMF is too much trouble to install try to get a 2GM20F its great and easy to work on.
I have a 2001 2GM20F fresh water cooled 18 horse power and it has plenty power for my 290 and uses very little fuel,so if the 3GMF is too much trouble to install try to get a 2GM20F its great and easy to work on.
You need dimensions.
You should be able to find the exact dimensions of both engines on the web. You especially need to know how the mounts differ. If the difference is significant you are in for a big expense for mounts for the 3GM. Not only position but angle. The shaft will need to be shortened for the 3GM. Are the two 2GMs identical? That is you know the newer 2GM is a drop in? Seems like a no-brainer. You know that you can make the 2GM a model 'F', fresh-water cooled. There are kits to add a heat exchanger and a waterpump. And the heat exchanger will have hose connections for a hot water heater. That is exactly what was done to my 2QM20, originally a raw-water cooled engine. Good luck with your upgrade.
You should be able to find the exact dimensions of both engines on the web. You especially need to know how the mounts differ. If the difference is significant you are in for a big expense for mounts for the 3GM. Not only position but angle. The shaft will need to be shortened for the 3GM. Are the two 2GMs identical? That is you know the newer 2GM is a drop in? Seems like a no-brainer. You know that you can make the 2GM a model 'F', fresh-water cooled. There are kits to add a heat exchanger and a waterpump. And the heat exchanger will have hose connections for a hot water heater. That is exactly what was done to my 2QM20, originally a raw-water cooled engine. Good luck with your upgrade.
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