71 stringer voltage regulator smoking when I turn key

[Knoll42]

I think I am in over my head with this boat. Out on the water running great and the motor dies. Wont start so i checked ignition fuse. Blown. Replaced 14 amp turned key motor fired then died blown fuse. I smelled smoke to the rear and removed engine cover. alternator has black soot around the front pulley wheel and the regulator smokes when fuse is replaced and key is turned then fuse blows.

It looks like the alternator may have been replaced in the past by the way it is rigged to the motor. It is rigged past the limit of the mount. Maybe the belt was streched or something anyway it seemed to work fine untill today.

I would hate to buy a new one just to watch it fry. Any input is realy appreciated
Motor Model nufm 12ax
Regulator Number VSH 6201
Alternator Number ALK 6210

 

[Howard Sterndrive]

Re: 71 stringer voltage regulator smoking when I turn key

the service replacement for those Prestolite externally regulated alternators is a 1-wire Delco with an internal regulator. It is a fairly strightforward conversion. You toss the regulator and alt overboard and the Delco mounts up and just 1 wire leaves it and goes to the batt terminal on the starter. (your existing 10 ga. alt output wire)- you eliminate all the rest.

It does sound like something failed in your alt. The regulator feels the added load, and then the fuse saves you from a fire.

here's a recent thread on conversion to Delco
http://forums.iboats.com/showthread.php?t=515416

the 1 - wire alternators are pretty reasonably priced these days... see them on eBay for under $100 - just make sure the one you get is marine

most of the ebay units are 100 - 110A, so you would also need to upgrade to a 100A breaker in the alt output wire (probably a 50A there now)

 

[Knoll42]

Re: 71 stringer voltage regulator smoking when I turn key

the service replacement for those Prestolite externally regulated alternators is a 1-wire Delco with an internal regulator. It is a fairly strightforward conversion. You toss the regulator and alt overboard and the Delco mounts up and just 1 wire leaves it and goes to the batt terminal on the starter. (your existing 10 ga. alt output wire)- you eliminate all the rest.

It does sound like something failed in your alt. The regulator feels the added load, and then the fuse saves you from a fire.

here's a recent thread on conversion to Delco
http://forums.iboats.com/showthread.php?t=515416

the 1 - wire alternators are pretty reasonably priced these days... see them on eBay for under $100 - just make sure the one you get is marine

most of the ebay units are 100 - 110A, so you would also need to upgrade to a 100A breaker in the alt output wire (probably a 50A there now)

The regulator smokes when the key is turned to the on position without the motor running. Would that by any chance be indicative of some other problem?
Thanks Sir

 

[Howard Sterndrive]

Re: 71 stringer voltage regulator smoking when I turn key

maybe, probably not, but the solution is the same regardless... spend $55 on a new, modern reliable alternator to replace the 40 year old antique.

 

[Knoll42]

Re: 71 stringer voltage regulator smoking when I turn key

RGR that. Thank you. I will post after I replace the parts.

 

[Knoll42]

Re: 71 stringer voltage regulator smoking when I turn key

Thank you Howard. The alternator brushes were grounded. Problem solved