1978 Black Max 150 hp Rectifier

[kevinj]

I'm posting this for a coworker.

He has a 1978 Black Max 150. We were talking today about getting boats prepped for the Memorial weekend and he mentioned he has the battery charging. He later said the battery is pretty much down every time they go out and unless he disconnects the battery, it will be completely drained. So, he removes the battery connections and charges it every time they use the boat.

So I asked him, "does you tach work". He said it does intermittently but most often it doesn't. This has been going on for the last 7 years he's owned the boat.

I've always owned Johnson/Evinrude engines, and I know on those if you're battery won't stay charged and the tach doesn't work that it's a sure sign the rectifier is shot. Would the same apply to this Merc 150? Are these engines CDI or were they still coil/condenser/points? Final question: Where is the rectifier on this engine? Is it on the stator base plate under the flywheel or is it on accessible on the side of the block of the engine?

Thanks.

KJ

 

[galamb]

Re: 1978 Black Max 150 Rectifier

The rectifier is a black diamond shaped, 3 post (thing) on the side of the powerhead.

It's fed by two (normally yellow or a yellow and grey) wire from under the flywheel.

It will have a red wire feeding over to the starter and a grey wire (or sometimes brown and sometimes purple) going to the harness (for the tach).

They are a generic part for many Merc outboards and sell (aftermarket) for about 35 bucks.

However, since the battery will "drain", it could also be a bad connection somewhere that's sucking the power...