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I’m curious if anybody has elected to put a smaller engine in the 424 or a similar sized boat? I ask as that seldom do I see vessels operated at their continuous rating RPM but often much less. The W60 is rated at 53 hp at 2500 rpm’s. When motoring I run around 1850 and attain 6.5 knots (I’m probably lightly overpitched). My thought is I’m using maybe 40 hp to move the boat. When I’m motorsailing, running even less rpms.
I’m toying with the idea of putting a 3JH5 in there rated at 39 hp at 3000 rpms. The engine is almost half the weight of the W60.The trend I see is getting the biggest engine in there that will fit. You guys with the >60hp engines, you use all that?
Chuck
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I haven’t done any calculations like Pete, but after dealing with all the currents in the ICW and trying to get though the cuts and passages in the Bahamas with my W58, My gut feeling is GO BIG. You might want to contact Jack Tyler the former owner of WHOOSH and see how he came up with his choice. He’s a pretty smart and articulate guy.
YMMV
ALan
UNABATED— On Sun, 2/12/12, Chuck Ruble wrote:
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Chuck,
I have a 75hp Yanmar. I never use 75hp but having the extra power doesn’t
hurt. I can back-off on the throttle to where the engine is just limping
along at what feels like a slow cruising speed. The boat will be doing
7.3kts. The engine is purring along at about 2500 RPm vs 3800 rmp for
full-throttle. At this throttle setting, the engine is pretty quiet. With
a good alignment, there is almost no vibration.The alternator uses about 6hp at full charge rate and the engine-driven
regrigeration loads another 6hp when the reefer gets cold. These usually
happen at opposite ends of a cruise period so I can usually figure a max 6hp
load from the accessories but its still 12 hp worst-case. Accessory loads
should be considered when sizing the engine. That’s why I went up a size.
Given that the cost of the engine can be less than half the cost of a
repower I see no reason to skimp there.I had a W60 previously. I don’t think that thing was really 53hp. I’d
guess it was really about 45hp. 75hp is probably overkill, but I wouldn’t
recommend anything smaller than 60hp.Hope this helps
Regards RichQuote:
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Chuck,
A friend of mine has a 42′ Hinckley and another has a 40′ Endeavour. They are both powered by a Perkins 4-108 engine. The HP is 51HP @ 4000rpm and substantially less at 2500rpm. They struggle against wind and current. I have motored with one eastward along the south coast of Grenada when the tradewinds were on the nose at 15kts and we barely achieved one knot going 2500 rpm. Not a good situation.
I repowered with a Yanmar 54 hp engine, naturally aspirated, and I have plenty of torque to match my previous engine, a Perkins 4-154, which was 62HP.. Torque is even more important than horsepower. This engine has performed very well. I preferred a naturally aspirated one vs a turbo so I don’t have to run at 3800 RPM every 10 hours to burn off carbon buildup. I was worried about possibly stressing out the drive train at that RPM level. This engine is the same as the 75HP turbo but its top RPM is 3000 rather than 3800. At 2500 rpm both engines deliver the same torque and HP and at that level, noise and vibration is low enough for a comfortable, and strong, ride.
Hope this helps,
Joe
Half Moon________________________________
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