Car alternator OK for my boat?

[Cromarty]

The alternator of my Volvo MD22 engine gave up after 26 years. A new one from Volvo costs a fortune, but I've been told that a car alternator will do just fine.

I've noticed, however, that a automotive alternator has fewer electrical contacts than the one on my Volvo (Perkins) engine. Apparently, there's a separate negative lead to the battery on the boat that is not there on a car.

Can I just go and buy a car alternator of the same capacity (60 Ah) and install it on my Volvo (Perkins) boat engine?

[Kalinka1]

have it rebuilt at an auto electric shop. Around a 100 to 200 here.

[Cromarty]

Originally Posted by Kalinka1

have it rebuilt at an auto electric shop. Around a 100 to 200 here.

I do not think any auto shop offers that service over here, but I'll certainly check. Boat dealers do offer refurbished ones but these are still 70% of the price of a new one...

[Neptune's Gear]

If its a factory alternator, and still internally regulated, then yes, many boats use automotive alts. Some boats use a -neg battery lead from the alt, some don't. Those that don't, rely on the engine block being connected to -neg.
If you have limited electricity demands on your boat, an automotive alt can be fine, but they are not designed to put lots of amp hours into a large bank....

[Cromarty]

Originally Posted by Neptune's Gear

If its a factory alternator, and still internally regulated, then yes, many boats use automotive alts. Some boats use a -neg battery lead from the alt, some don't. Those that don't, rely on the engine block being connected to -neg.
If you have limited electricity demands on your boat, an automotive alt can be fine, but they are not designed to put lots of amp hours into a large bank....

It's still the factory alternator, from Volvo. It puts 70ah in one bank of two service batteries (240 amps together) and one starter battery (120 Ah). This has worked fine for 26 years, so I guess the 60 Ah of the factory alternator is sufficient. Moreover, The boat has shore power most of the time and so batteries are trickle charged then.

But could there be a safety problem with a diesel engine and unshielded sparking from an automotive alternator? I did not think so, but correct me if I'm wrong.

[Neptune's Gear]

No, it will be fine. The original alternator is nothing special. Its actually just a standard automotive alt anyway.
For a boat that returns frequently to shore power, it will be fine, as the other one has been.
Its likely all the old alt needs is bearings and brushes....

[Cromarty]

Originally Posted by Neptune's Gear

No, it will be fine. The original alternator is nothing special. Its actually just a standard automotive alt anyway.
For a boat that returns frequently to shore power, it will be fine, as the other one has been.
Its likely all the old alt needs is bearings and brushes....

OK, thank you very much for this useful information. I might go and check if I can find a repair shop for the alt. But, given the relatively low prices of new automative ones, I doubt if it will be worth while the hassle of having the old one repaired...

[Dockhead]

Originally Posted by Cromarty

OK, thank you very much for this useful information. I might go and check if I can find a repair shop for the alt. But, given the relatively low prices of new automative ones, I doubt if it will be worth while the hassle of having the old one repaired...

You've gotten good advice.

As everyone said, no problem using a car alternator, BUT -- there are several different wiring schemes, and not just concerning the ground. If you don't want to do any rewiring, you want to match up the wiring scheme of the new one to the old one.

That being said - I would just rebuild the old one. Could be less than 100 euros depending on what is needed, and no hassle adapting anything or figuring out the wiring.. Should not be hard to find a shop - this is a very, very very common service.

On the money you save, invest into an external regulator.

[Island Time O25]

My 36 footer had an early 90s Powerline 120amp alternator. When it gave up the ghost my first inclination was to have it rebuilt. 3 shops gave me estimates of between $200 and $400 for what I thought would be a simple $100 job. The company was out of business by that time and the equivalent Motorola or Hitachi units were between $650 and $850 plus delivery, taxes, etc.

Upon advice of my diesel mechanic buddy, who at that time happened to be the head of maintenance for a large (80+ boats) charter sailing club here in the city, went with a brand new 110amp Chinese knockoff from ebay for $70 delivered. My idea was that if I had to replace that alternator every other season or so I'd still be ahead of the game compared to buying $800 one. Five seasons later it is still working fine charging a bank of 3 2X6Vs 115 Trojans. No shore power as I am on the mooring but 440W of solar sure helps and keeps the need to run the engine to a minimum - on rainy/cloudy days only, if at all.

[valhalla360]

Just a note for others reading: This applies to small diesel engines.

For gas inboard engines, it's a different ballgame as marine alternators are spark protected to protect against explosive fumes.

[Pete7]

Some alternatives:

http://www.parts4engines.com/volvo-penta-2000-series/

https://www.google.co.uk/url?sa=t&rc...-pz4o9FUBB8nPg

https://www.google.co.uk/url?sa=t&rc...KfD99YSJ7mJmJA

https://www.google.co.uk/url?sa=t&rc...HGaKpvWVthQmkA

If that doesn't produce a better price then lots on e bay UK.

Pete

[nigel1]

I had one of these to replace the alternator from my Volvo Penta TMD 22
https://www.dfjauto.com/DFJ010261?gc...SABEgLrAfD_BwE

Connections were exactly the same as original alternator, B+, B-, W and D.
The back of the original alternator is stamped VALEO. Volvo just paint them green, and triple the price.

I have an external regulator connected which does improve the efficiency of the alternator.

[nigel1]

If you look at this page
https://www.marinepartseurope.com/en...50-30-448.aspx
It indicates that the volvo alternator is 60A.

[Cheechako]

No worries with the car alternator. It must be one that fits and aligns properly though. Some marine alternators are more heavy duty, bigger diodes etc than some car alternators. Especially the typical modern car alternator which isnt designed for heavy charging at all. There are also new alternators on Ebay. Maybe search for a "Marine" alternator that fits your engine type.

[taxwizz]

Add the word "Marine" to any product and double the price.

Add the word "Aircraft" to any product and quintuple the price.

With no changes needed to the product.