CD27 Yanmar engine replacement?

[G. Bauer]

I have a CD27 hull 239 (1982) powered with a Yanmar one-lung 8-hp diesel. It's not enough for the frequent currents / headwinds in our area (east coast, NY/NJ/Conn.). Has anyone had experience repowering with a larger engine? I'm looking particularly at the Yanmar 2 cylinder 12-hp, which is only slightly larger.



bauerg@moodys.com

[Bob B.]

I had the same problem with my CD27 on the coast of NC. I checked into repowering and you are looking at 5-7 thousand dollars unless you can do the work yourself. I chose to read my tide tables carefully and go slow. I did have an overhaul done on the 8hp and it picked up a little in that mine had lost compression. In the end, I wish I would have gone to the 12hp since I spent 2,000 anyway and still had an undersized engine.
Good luck with it.
BobB



BundyR@aol.com

[chuck yahrling]

I have a CD27 hull 239 (1982) powered with a Yanmar one-lung 8-hp diesel. It's not enough for the frequent currents / headwinds in our area (east coast, NY/NJ/Conn.). Has anyone had experience repowering with a larger engine? I'm looking particularly at the Yanmar 2 cylinder 12-hp, which is only slightly larger.

My 1982 CD-27 appears to have come from the factory with a 2GM, rated at 13hp. It's a nice fit in the engine room and is more than adequate for the 1-2 knot currents I experience on the Kennebunk River. It would be a worthwhile effort to upgrade if you can find a 2GM for a reasonable price. Otherwise, I would go with the newer 2GM20, which is also substantially lighter.

I run my 2GM at 2500 rpm and get a little over 4kts as verified by comparing gps and knotmeter. At 3200 rpm it goes about a half a knot faster. Reverse power is ok, but directional control in reverse is typically dicey until the the boat gets some way on. If I had the 2GM20 I would consider getting a 3 blade or repitching the prop I have.



yahrling@cybertours.com

[Bill Goldsmith]

My 1980 CD27 was repowered about 10 years ago with a Yanmar 2GM20F. It is rated at 18hp at max rpm, but 16 hp at recommended rpm. This engine really gets the boat out of its own way. I motor at about 2500rpm and get about 5 knots in calm water. I have a 2-blade. Why would you recommend a 3-blade? Great engine.

Bill Goldsmith

I have a CD27 hull 239 (1982) powered with a Yanmar one-lung 8-hp diesel. It's not enough for the frequent currents / headwinds in our area (east coast, NY/NJ/Conn.). Has anyone had experience repowering with a larger engine? I'm looking particularly at the Yanmar 2 cylinder 12-hp, which is only slightly larger.

My 1982 CD-27 appears to have come from the factory with a 2GM, rated at 13hp. It's a nice fit in the engine room and is more than adequate for the 1-2 knot currents I experience on the Kennebunk River. It would be a worthwhile effort to upgrade if you can find a 2GM for a reasonable price. Otherwise, I would go with the newer 2GM20, which is also substantially lighter.

I run my 2GM at 2500 rpm and get a little over 4kts as verified by comparing gps and knotmeter. At 3200 rpm it goes about a half a knot faster. Reverse power is ok, but directional control in reverse is typically dicey until the the boat gets some way on. If I had the 2GM20 I would consider getting a 3 blade or repitching the prop I have.

goldy@bestweb.net

[chuck yahrling]

My 1980 CD27 was repowered about 10 years ago with a Yanmar 2GM20F. It is rated at 18hp at max rpm, but 16 hp at recommended rpm. This engine really gets the boat out of its own way. I motor at about 2500rpm and get about 5 knots in calm water. I have a 2-blade. Why would you recommend a 3-blade? Great engine.

Bill Goldsmith

I have a CD27 hull 239 (1982) powered with a Yanmar one-lung 8-hp diesel. It's not enough for the frequent currents / headwinds in our area (east coast, NY/NJ/Conn.). Has anyone had experience repowering with a larger engine? I'm looking particularly at the Yanmar 2 cylinder 12-hp, which is only slightly larger.

My 1982 CD-27 appears to have come from the factory with a 2GM, rated at 13hp. It's a nice fit in the engine room and is more than adequate for the 1-2 knot currents I experience on the Kennebunk River. It would be a worthwhile effort to upgrade if you can find a 2GM for a reasonable price. Otherwise, I would go with the newer 2GM20, which is also substantially lighter.

I run my 2GM at 2500 rpm and get a little over 4kts as verified by comparing gps and knotmeter. At 3200 rpm it goes about a half a knot faster. Reverse power is ok, but directional control in reverse is typically dicey until the the boat gets some way on. If I had the 2GM20 I would consider getting a 3 blade or repitching the prop I have.

I'd investigate a 3-blade because there's only so much push you can get out of a given amount of blade area, regardless of how much shaft horsepower is driving it. In fact, I'm fairly sure that's why I only get another half a knot or so out of the extra 700 RPM as explained above, e.g. a lot is lost through slippage. Both our boats are capable of close to 6 knots hull speed, and I bet we could both benefit from a three blade prop's extra area.

Note that high-performance fighter aircraft in WWII used 4 and 5 blade props with huge paddle blades to get all their thousands of HP translated into usefull push, despite the fact that a two-blade prop is theoretically more efficient.