MD11C Alternator

[mjscottinnc]

I'm just wondering if anyone has worked on the alternator on the Volvo MD11C. I just purchased the boat and have found that the alternator is putting out very high voltage, actually killed all the electronics except the VHF. In researching it seems that the voltage regulator is bolted to / and part of the alternator. Has anyone gone down this road before? Is it worth fixing or should I just purchase a new one?

[rbrtfeld]

Is this an original Volvo Alternator? That does not sound good. I replaced my original with a 100 amp high output Alternator. Anything at 100 or more should have an external regulator. Are you sure it was the Alternator that fried your electronics? I think it would be worth your time and money since you just purchased the boat to hire a professional marine electrician to look over your entire system. I learned more in a couple of hours from my electrician than I could have in a year reading about what to do about a problem. Good luck

[mjscottinnc]

I'm guessing that it is the original alternator with an internal voltage regulator and it does not appear that anyone has performed 'boatyard engineering'

I whole hearted agree a professional assessment is needed... so since I've been an electrical design engineer for over 45 years and own an electronics manufacturing company, I'm going to go with my assessment. With the boat motoring and the volt meter over 20 volts, your only real choice is the voltage regulator.

As for killing the electronics, I opened up the depth finder and saw that the main controller chip has a large piece missing from the middle of the plastic chip package. That only happens when the voltage to the chip is so high that it literally blows its top.

I'm just wondering what other people have found with a similar failure.

[rbrtfeld]

Sounds like you have it figured out. I am headed to my boat on the 28th for a week. If you cant find a fix,I still have my original alternator in a locker somewhere, you are welcome to it if you pay the shipping. It was working when I replaced it for the 100 amp one I currently have. Send me your contact info to rbrtfeld@aol.com.

[mjscottinnc]

I bought a 100 amps as well. I found that the OEM tensioning bracket will not fit correctly as is. The new alternator has a slightly bigger body diameter (they say it is still a DELCO 10SI type) and the stock alternator bracket for the MD11 does not have a radiused slot to follow the arc of the mounting, it has a straight slot. Must have been a production cost issue, or bad engineering. I figure I have two options, the first one is to loosen up bracket and rotate the bracket a bit higher and put a small twist in the arm to get the straight slot on the same plane as the mounting hole. If that fails, I'll have to remove the bracket, take some measurements and design a new bracket with the correct arc slot, get my metal guy to CNC cut it, two bends at the office and it should be an exact fit.

[dmellon]

What do you use for a drive belt (belts) on the 100 amp alt? Some have slippage with single belt.