New Yanmar With or Without Generator ???

[Greg Debi Josh]

We are re-powering with a new Yanmar 4JH5E and notice that it is offered with the option of a generator built in between the engine and and the geabox.

Does anyone have any advice on this engine and on this gearbox option please.
Much appreciate it as we are about to spend big bucks. Thanks.

[nauticalnomad]

Originally Posted by Greg Debi Josh

We are re-powering with a new Yanmar 4JH5E and notice that it is offered with the option of a generator built in between the engine and and the geabox.

Does anyone have any advice on this engine and on this gearbox option please.
Much appreciate it as we are about to spend big bucks. Thanks.

Ive just bought a nanni 43hp to replace a 4107 and they had that option.
I couldnt justify the extra expense for what i use,
It depends on what boat you have,
I have a sailing boat im prepping for long distance etc
So i the only things i have is laptop and nav stuff,
I dont watch tv etc.
I went hydraulic propulsion as well to replace a vee drive and there is an otption for a 10kva hydraulic genset i still couldnt justify the expense for the extra fuel for what i need power for.
If i had a power boat and wasnt looking for long distance i would have got one for sure.

[Play Actor]

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.

[Greg Debi Josh]

Thanks again Bud, our present propellor is marked 17 x 12 three blade? What in fact does this indicate? Staff at Budget and Island Water World don't seem to know either....
Do you also perhaps know if there are shaft extensions as the new motor is very much smaller than the old Ford? I really don't wish to buy a new shaft. Our present shaft seems a strange size - 32mm, maybe it is imperial one and a quarter?
Thanks Greg

[Cheechako]

That would be 17" diameter and 12" pitch. The pitch being the theoretical amount of travel forward in one revolution. A shaft usually isnt too expensive, and you might find you have a pretty good grove worn in your old one inside the packing area. Worth checking anyway.

[delmarrey]

I'd skip the gen, between the motor and trams, setup. If you need extra DC power there is the two, front mounted, alternator option, that allows EZ access for repairs. If something happens to the middle one, it would be a nightmare to work on.

With the motor being shorter you can move it back a bit but either way you'll probably need the motor bed reworked. I'd go with a new prop shaft either english or metric, depending on your strut. If the strut cutless bearing OD is metric, stick with it. And just re-prop to match the boat and running gear.

Sometimes it's better to just go all new then trying to re-rig old equipment to match up.

If the old prop is out of pitch but in good shape, some shops will give you a trade in value when purchasing a new prop. Or it could be sold online.

[Play Actor]

Greg,

Cheechako answered the prop question. Is it LH or RH? LH rotates counterclockwise in forward. The Yanmars rotate clockwise in forward.

Did you figure out the gear ratio?

And I have to ask if you're sure you need the 4JH5. That was my first choice, until I really dug into it, and I'm glad I did. The dealer is likely to err on the side of the larger one. Find out what hp engines other folks with your boat or similar are using, and how they're performing. The extra size and weight, not to mention cost to buy and run make it worth studying.

Once you've got the engine and transmission picked out, spend some time on the phone with a good prop shop -- I can recommend West by North, up in British Columbia. Google will get you there. Norm is a walking encyclopedia of what prop works with what boat and engine. Even if you don't buy a prop, it's a sanity check.

A good machinist might make a shaft extension, but I'm not sure that would save you much, and it's one more spot for flex and misalignment. The metric shaft will have a metric taper for the prop, unless somebody machined it to an SAE taper. That could be another headache if you need to swap the prop. A new shaft isn't much in the scheme of replacing the engine. I paid about $600 US for an 8 foot length of 1 1/4" shaft at Budget in St. Martin. It already had a taper for the prop. I had it cut to length and had a keyway machined in for another $75. I know it seems like an endless stream of expense, but, if you have to do it, it's worth doing a first class job. Mine gets cheaper everytime I use it.

You could probably save some money and have access to more skilled help if you could get the boat to St. Martin. As much as we love Grenada, the difference in working on the boat in St. Martin vs. there really is dramatic.

Good Luck,
Bud