I have an opportunity to replace the Yanmar 2GM20F in my Hunter 326 with a Yanmar 3GM which would be a big improvement as the 2GM20F seems to be underpowered for a boat this size, weight and length. Has anybody undertaken an engine changeout like this and if so have you encountered problems that would wave me off from doing so?
replacing a 2GM20F with a 3GM20
- Thread starter Rick R
- Start date
I haven't done one, but it looks like you'll need to space the motor mounts up a bit to accommodate the bigger engine. A quick look at the drawings (not positive these are the exact ones for your engines) says that the mounts are exactly the same width, so all the work is going to be in getting the new mounts at the correct elevations so that the prop shaft lines up. The new engine would be smidge more than 5 inches longer from the transmission output flange to the front of the engine. The output flange is a little under a quarter of an inch lower from underside of the motor mount.. so it ends up being a trigonomics problem. Most folks who've changed engines have built a plywood "buck" that locates the engine mounts and the output flange of the new engine. They then use the "buck" to get the engine mounts spaced vertically. (after verifying that the new engine will fit in the space in the boat).
Sounds like an interesting project..
Maine Sail has a video of the grunt part: https://www.youtube.com/watch?v=mtJy4ytdSWY
Sounds like an interesting project..
Maine Sail has a video of the grunt part: https://www.youtube.com/watch?v=mtJy4ytdSWY
You need to account for the increased size of the 3GM.
Verify whether the 3GM is freshwater or sea water cooled. In either case pay attention whether the sea water intake aligns with your present sea water sea cock and if not then whether you can make modifications.
Verify motor mount fore and aft position and and width. Measure the 3GM to verify motor mount position changes. Use the transmission output flange as your common reference. See if the forward-most part of the 3GM interferes with some part of the boat (usually fixed cabinetry) Otherwise - you might need to shorten/lengthen the prop shaft.
Exhaust/cooling water ell position. Verify the current position of the connection is similar to the 2GM. If not then can you make changes that are convenient.
Other considerations include whether fuel supply/return lines/primary filters are located such that you can modify or move them - and thus have access when the larger, longer 3GM is in place.
No doubt you will find other interferences and compromises but these are the main things.
Charles
Edit Looks like I sent mine before I saw Kloudie1. Either way the message is determine whether things will be easy or extensive. Better you should know what is likely to happen before you start.
Verify whether the 3GM is freshwater or sea water cooled. In either case pay attention whether the sea water intake aligns with your present sea water sea cock and if not then whether you can make modifications.
Verify motor mount fore and aft position and and width. Measure the 3GM to verify motor mount position changes. Use the transmission output flange as your common reference. See if the forward-most part of the 3GM interferes with some part of the boat (usually fixed cabinetry) Otherwise - you might need to shorten/lengthen the prop shaft.
Exhaust/cooling water ell position. Verify the current position of the connection is similar to the 2GM. If not then can you make changes that are convenient.
Other considerations include whether fuel supply/return lines/primary filters are located such that you can modify or move them - and thus have access when the larger, longer 3GM is in place.
No doubt you will find other interferences and compromises but these are the main things.
Charles
Edit Looks like I sent mine before I saw Kloudie1. Either way the message is determine whether things will be easy or extensive. Better you should know what is likely to happen before you start.