Perkins Prima M50 Alternator

[joemac4sail]

Hi all
I'm looking for a bit of help identifying the Alternator that was fitted as standard to the Perkins Prima M50 The engine in question is a 1991 vintage, and I think that replacing the regulator and brushes will rectify a minor problem (not charging) unfortunatly I'm nowhere near the boat to check and my next visit will be to do the service.
Any help would be appreciated.
Regards Joe McDonnell

[Kyoko]

Hi
I have the same engine and it had a Prestolite 127 (same as Lucas) alternator.
mine was a 70 amp but it could be a 55 amp.
You can find regulator/brush set on Ebay.

[joemac4sail]

Thanks Kyoko for the information, hopefully the brushes will sort out the problem of the alternatoer not charging. Its just another one of the bits added on to the engine that we have had to work on in the past year. I intend bringing out to the boat (in Alghero), a Bosch 120 amp alternator and smart charger, but having the original alt. as a back-up will ease my concerns.
Regards Joe

[Kyoko]

Hi again !
Good thinking, I bought a 100 amp alternator and fitted a Sterling pdar external regulator, works great, It keeps my batteres almost fully charged when motoring for a while, I also fitted 2 x 100w solar to maintain the autopilot and navigation when sailing

[JWK]

I have a similar intermittent problem with a Perkins M50 engine and instrument panel. The ignition key is a simple on/off switch that powers up the panel. There are momentary contact push button switches for the glow plugs, starter and stop solenoid. When the key is turned on the alarm buzzer sounds and the "battery" light the fuel gauge come on; depressing the start button activates the starter or nothing happens.

If the starter engages the engine starts immediately but the battery light does not go out and the Tach does not operate. As the engine warms and is operated at normal RPM the Tach eventually comes on and the battery light goes out and everything operates correctly.

The alternator was rebuilt a few months ago when the intermittent problem first arose; it puts out 14+ volts at an idle. The shop doing the work said they didn’t find anything wrong. I’ve checked and cleaned all the connectors, harness plugs etc., and concluded that the problem is likely in one off the three relays in the system or possibly one or more of the switches.

The switches look ok and appear to function correctly so I’ve ordered new relays assuming that they are the likely failure point. I’d be interested in other M50 owner’s experiences with the panel, switches and relays.

Jim

[Stu Jackson]

Originally Posted by JWK

If the starter engages the engine starts immediately but the battery light does not go out and the Tach does not operate. As the engine warms and is operated at normal RPM the Tach eventually comes on and the battery light goes out and everything operates correctly.

Jim, does your regulator have a built in delay? Ours has a 45 second (adjustable) delay.

[JWK]

Stu, I don't know about an automatic delay. It takes minutes before the light goes out and the Tach starts working.

How do you adjust the delay?

Jim

[twinboat]

Sounds like loose belt.

[JWK]

Thanks for the comment about the belt; it's adjusted properly.

[JdaleH]

Check out the ground fuses in the wiring harness. Look for two lumps in the harness near the starter. Dale