Good evening all. I have joy to report, today My engine started and ran only a short time as the was no seawater cooling available. Getting there one step at a time. However, it seems the alternator hasn’t fared as good during it’s dormancy. During the short engine run, there was no tach reading and it was discovered that the alternator was smoking. So I think I’m now faced with locating a replacement, and that is why I am calling upon anyone with the same experience for guidance. I have already determined that the engine is a Mitsubishi K2A and the alternator is stamped with Mitsubishi. Does anyone here know of a source or even cross reference information for this alternator?
I am hoping to launch before the end of January so I have some time plus I still have a few more outstanding projects to complete.
Any help would be mucho appreciated.
I suggest finding a local alternator shop and take your old one in. They are pretty commonly available, but if you look to purchase a ‘Westerbeke’ you will pay a massive premium.
Bob Gehrman
NS30U #396 “Quickbeam”
Baltimore, Maryland
You can get them rebuilt for a reasonable price. It makes a good spare and when you have a spare you never need it… that is the "rule of spares’
As previously mentioned $160 is about right, there is nothing special about these alternators. A 90 amp alternator will run cooler than a 50 across the same battery bank.
Don’t everyone get too generous with Ron’s horsepower. According to Westerbeke’s specs the W-10 can give 10hp but it is rated at 9 at 3600 rpm.At a more reasonable 24-2600 rpm it is putting out between 7 and 8 hp. 90 amps is about 1.45 hp. Let us assume low batteries so the alternator is putting out power. Further assume if the alternator pulleys are sized to give full rpm at 3600 we can say about 60 amps at 2500 rpm. With loss due to heat that will be using up about 1hp or about 12.5% of available power. With losses due to inefficiencies in the prop and the angle of the prop shaft Ron could be down to 5 hp to move the boat.
Ron take careful measurements of the available space before you invest in a larger alternator. Some of the engine designs simply don’t have room for a larger alternator.
Don’t forget that you should not run lead acid batteries (this includes Gel and AGM) below about 50% on a regular basis. The charge acceptance rate of this type of battery drops rapidly once you get into the 65% to 70% state of charge. Here is a link to an article in Marine How To about charging AGM batteries. how-fast-can-an-agm-battery-be-charged
He is charging a 105 amp hr battery. At about 63% state of charge the battery would not accept more than 41.5 amps.
The general rule of sizing an alternator is to have between 20 and 40% of your battery bank. So 20 to 40 amp alternator for a 100 amp hr battery bank. You do need to allow for some efficiency so probably 30 to 50 amp alternator for a 100 amp hr battery bank is considered good. IF you have 200 amp hr bank then double but keep in mind the limits on hp and mounting room.
La Reina has a 75 amp alternator but I have yet to see more than 30 amps going into the batteries.
I don’t want to bend the thread here but I am curious about something. Ron - Sorry if I missed this but what battery(s) are you running ? Are you on a slip with shorepower and, if so, what kind of charger do you have and what shape is it in ?
Hey, thanks all for such an outpouring of information. Today I explored the possibility of getting mine rebuilt and as Mariner’s Cat suggested to use as a spare, but there are no shops in my neighborhood that can do a rebuild. I am zeroing in on some possible sources for a new one - Westerbeke wants $850.00 for theirs.
Joe - that number 30594 keeps popping up in my research, but my impression is that it is for the W27, please correct me if I am mistaken. If it works on my W10 that would enhance my chances of getting a replacement - I’ve seen a number of those.
Mark - I welcome your technical perspective, something I would not have known to consider as I am sure most would be recommending upping the output, and above all I want this to be a long term reliable solution. I will be reading your links this evening.
Ernie - I will be replacing my batteries with two Mastervolt 90AH group 31. I will be installing a 100 watt solar panel, and I rarely use shore power. We are pretty power frugal as all the lights are LED, underway we use a small GPS and depth finder. The biggest consumer on the boat is the 35qt Engel fridge with a power consumption of 2.5 amps so I figure less than 2 amps average, and I turn it off late at night after it will no longer be opened. I gave my wife all the technical reasons that we can’t have a microwave onboard (shucks Honey I wish we could).
I would like to add a side note, something obviously you all are already aware of but it feels good to say . I’ve owned 10 boats over the years, all small and ranging from trimarans to slow poke pocket cruisers, but none of these boats had the level of quality of design and build that my N22 has. I have done extensive renovations and upfitting and this boat hasn’t made any of these tasks unnecessarily difficult and the results have been just what I had hoped. This boat really does have the heart of a fine yacht and I am excited to feel her reaction to wind and waves.
I will provide an update as soon as I resolve the alternator issue. Thanks again all.
Joe - thanks for that, however my W10 has a 35 amp original part #32939 (no longer available) replaced with part #39268. I don’t know the difference, except that the 50amp model is much cheaper and more readily available than this puny little 35 amp model. It seems that API may be the only manufacturer for this model. So I will probably order the API ($355.00) and try to find a rebuild shop in my part of Florida to see if they can refurbish my old one for a spare.
Once again - thanks to all for your valuable information.
Westerbeke show the same alternator for many designs of engines and gen sets that used that same Mitsubishi block. The original alternator is most likely a Nipponedo as was the lift pump. They are now part of Denso. But I had no luck trying to cross reference the Westerbeke part at Denso.
Thank you for your research. I did locate and have ordered a new alternator manufactured by IPA. The original alt on my W10 was a 35 amp. The bigger Westerbekes had bigger alts and were mostly 50 amp, that is the 30594 part number mentioned above. I think the difference may be that the windings are bigger and require a bigger case, so the foot bracket is wider (2 1/8"). I would have tried one of those like the ARCO, but was concerned that there may not be adequate clearance on my motor, and I’m not so sure any of these companies would be willing to accept the return of an alternator.
Hopefully I will receive it this week and it will fit. If everything goes well I will absolutely provide all the details incase any one finds themselves in the same predicament. I’m guessing they are hard to find because this K2 block seems to be the only one to use this particular model alternator. As I have the time I will be searching for an alternative source, as you suggest a tractor our industrial equipment parts place.
Once again thanks all and I will share an update.
I think I had the same engine as you when I bought N22 #35. It was locked up, and in spite of my best efforts I ended up getting her a new diesel. I have the Westerbeke W10 parts list which includes a beautiful (to me) electrical schematic. Also the operator’s manual, but it has been temporarily misplaced. If you want these let me know and I will send them to you USPS.
After a ton of web diving and with the help of folks here on this forum I learned some basics. The W10 is based on a Mitsubishi K2 block. The original alternator was 35 amps and had a proportionately smaller case than alternators of higher out put. Many of the bigger Westerbekes shared a common alternator which is still readily available and not too pricey. Finding a replacement alternator for the W10 was a challenge, and when I attempted to install it today, it proved to be less than a drop in replacement, although the modifications required to make it fit are manageable. The only sources I didn’t investigate are farm or industrial equipment parts suppliers as this K2 block was used for many such applications. Through it all I did learn important things about my boat that will certainly come in handy in the future, hopefully not the too near future. A part of what I learned is that the older diesels like the W10 employed mechanical fuel injection as opposed to electronic fuel injection so once they are started need no electrical current to operate. So instead of carrying a spare alternator, my two group 31 batteries and a 100watt solar panel should provide redundancy enough to get me safely to where ever I can find a cold beer.
Thank you for the offer of the manuals, but the previous owners of my N22 like most Nonsuch owners were conscientious and handed down those two manuals in good order. They have proved to be worth their weight in gold or even stainless steel.
When you get your new alternator installed, please ensure that 12v and ground are correctly attached to the alternator leads.
From what I read, if there is no connection to the batteries when the alternator is turning, it can burn out. No experience, just from what I’ve read. My NS26 still has the diode isolator permanently connected in, and I’ll replace it (most likely) with a FET based one. It has good points and bad points, but the good point is no matter what I do, the alternator always has a path to the battery.
Same with old battery switches, the “1” - “both” - “2” - “off” style; if it gets worn or dirty, switching it when the engine is running can lead to a temporary disconnect - with resulting troubles.
There’s a good youtube channel by pacific yacht systems, if you are bored sometime, go and watch a video or two; very informative.
Thanks for the heads up. Mine has a “Professional Marine” device which I am guessing is the protection you are referring to. My original alternator burned out when the motor was first started after sitting for over a year. The battery switch was definitely connected as the motor had just been started. I’m thinking it must have been it’s time as it looked pretty old. Seems like electrical things break when not used for a while.
One additional note: I had to modify this “replacement” alternator to physically fit. I had to grind off a bushing which protruded from the mounting foot, and the original adjuster arm (bracket) doesn’t connect because the ear on the new unit is shorter than the old one and the arm doesn’t clear the case. I purchased a universal bracket that is curved and will cut it to length. Hopefully that will work, but I will need a longer belt.
