2nd Alternator on Yanmar 3JH4 E

[Abraxas33]

I've just fitted a new 39HP Yanmar with a Hitachi 60 amp alternator and now want to fit my old 105 amp Prestolite as a second unit (liveaboard boat with 550 amp/hour battery capacity). Has anyone experience of fitting a second alternator to this engine as good spots to attach brackets to seem few and far between?

Thanks
Garry

 

[pvb]

Use the Yanmar bracket...

I'm sure you'll find that using the genuine Yanmar second alternator bracket will be the easiest and most reliable way of adding another alternator. However, it might not work if your Prestolite is a large case unit, and you might need to go for a slightly lower output (say 90A) instead, which would still be fine for your battery bank size.

 

[temptress]

I have 2 alternators on mine and had a customised bracket and flyweel built and mounted on the engine.

Limiting factor is space around the engine. You will also need to review your charge regulators/splitting dioeds etc. otherwise you may not be able to benefit form all the potential extra AMPS.

If space permits it's not too difficult....

 

[David2452]

Or, if you don't already have one, you could look at a more sophisticated charging set up to get the best out of your existing alternator as standard setups are highly inefficient compared to the latest generation of solid state devices.



David

 

[Abraxas33]

There's plenty of space; the problem is where to bracket off this particular engine. I've mailed my local Yanmar agent to see if they can supply brackets. I've always used Adverc for smart charging but it failed on the new alternator so I purchased a less expensive Sterling which works most of the time but trips quite often, Sterling don't seem willing to accept it could be their fault but all readings are well within tolerence (measured with high end Fluke with data logging facilities. Don't know yet whether I'll go for one smart reg controlling both alternators or separate regs (to avoid common mode failure). Either way I'll get the Adverc repaired.

 

[pvb]

There are some prices on this US website for the add-on bracket etc. Looks much cheaper than the Volvo one I bought for my 2003T (that's a surprise!). The advantage of getting the manufacturer's bracket is that they'll have investigated all the possibilities and gone for the one which works best. I originally fitted a 130A large-case alternator on my engine as the second alternator, but it was too heavy for the bracket and vibrated alarmingly. Sold it and fitted a 90A Prestolite small-case unit, which works a treat. I have the original engine alternator (with its integral regulator) directly charging the start battery, and the 90A unit (with Adverc regulator) directly charging the 660Ah domestic bank.