We put in a 3JH5E -- same engine, but 3 cyl vs 4 -- this time last year. We studied the 4JH5E, but decided the 3 was adequate for our 24,000 lb boat, and it turned out well.
Thought briefly about that generator, but it was only availble for 220V, 50Hz, which didn't suit, and we didn't really need it. We have a 1500 W. inverter
which meets all our needs. I agree with the previous post on that.
We also passed on the option of a high output alternator
and spent the money
to upgrade our solar panels
. Now we only run the engine to move the boat; for us, a better option. So, as intriguing as that generator was, we're glad we didn't do it.
We ordered the KM35A2 trans. with 2.33 ratio, but that depends on your boat and prop. As a starting point, calculate the prop shaft RPM
at your normal cruising RPM
for the old engine. Then, figure the likely cruising RPM for the new engine. The 3 and 4JH5Es both have WOT RPM of 3000. We used a 75% cruise
RPM, or 2250. Divide the cruise
RPM of the new engine by the desired prop shaft RPM, and you'll get the gear
ratio. It won't come out exactly, but it will give you a good idea of what you need.
That assumes that the old prop was performing satisfactorily. If you're going with a new prop as well, start from there. A larger diameter prop turning more slowly is generally more efficient, but you probably need the help of a good prop shop if you want to get into that. Our shaft rotation changed from LH to RH, so we needed a new prop anyway, but our max diameter is limited by the aperture. We stayed at the same diameter and shaft RPM and bought a slightly different pitch
. Our performance under power improved dramatically, mostly because we were overpropped with the old arrangement. Our cruise RPM is about 2200, and we can reach hull speed
at the 3000 RPM WOT with no problem and no engine overload.
Lots of detail, photos, etc. on the engine project
on our blog. The link is below. We usually spend every hurricane
season aboard in Grenada
. It's probably our favorite island. Good luck.