Alternator working or not?

[sahona]

The Sev I have in stock came from an MD11d if that's a help.
Don't wish to counter Ash, but a small pulley on the alt is a bonus - well worth the cost of new belts (remember the spare!) if required, as it gives full amps earlier in the engine rev curve.

[aquaplane]

I was thinking it would be fairly easy to adapt a different alternator to fit. From the front of the mounting to the middle of the pully it's 25mm which sounds like it could be a standard size. I hope the pullys are interchangeable but I'll avoid a groved belt if I end up looking in a scrappers.

The mounting looks like this:


A 1.2 Clio alternator may work, they are 70 amp but the ones I have found new say they are 12V, will that mean they are for a 12V system but kick out 14V for charging when required?

[DaveS]

I was thinking it would be fairly easy to adapt a different alternator to fit. From the front of the mounting to the middle of the pully it's 25mm which sounds like it could be a standard size. I hope the pullys are interchangeable but I'll avoid a groved belt if I end up looking in a scrappers.

The mounting looks like this:


A 1.2 Clio alternator may work, they are 70 amp but the ones I have found new say they are 12V, will that mean they are for a 12V system but kick out 14V for charging when required?

Yes, the 12V here means the battery voltage, 12V as opposed to 24V. I would expect a charging voltage of between 14V and 14.4V.

I agree with Sahona - if you can get one with a smaller pulley that's a bonus. The only down side is possible high load when starting from cold stalling the engine, but if that's an issue you can put a switch into the field circuit to keep the alternator off until the engine's warmed up. I do this with the power supply to my "smart" alternator booster so that it can be switched off if the engine is struggling.

[sahona]

Yea, that green thing (is it the Mekon?) looks the same as the one we had. You'll notice how the pulleys are almost the same size which means not many whizzamps without your eyeballs being shaken out of your head.
I got a 2" diameter pulley made by a mate which helps.
I did see an alternator with a small pulley in a VW I think, but it was heavily offset so may not be suitable in this instance.

Good luck.

[ash]

OK guys - I'll concede the point on the alternator pulley size - I was thinking that the drive pulley was the outside of the flywheel - like this



Bob's picture shows that the drive pulley is much smaller



I don't know what the max revs of a MD11C, but it will be a lot less than a car or even the 3,600 rpm of a Beta so an alternator with a 'standard' pulley wouldn't be overrevved.

I leave my O/1/B/2 switch on start battery during manouvres with a cold engine because the load of recharging the domestic battery will slow the 13.5hp Beta down - even with the standard 40A alternator. My Beta will push 10A into a 85AHr domestic battery sitting at 70% charge when at idle speed.

This shows the pulley sizes on my BZ482, 13.5hp Beta



Ash

BTW - My engine is now fitted with a filter on the raw water intake.

[aquaplane]

Ash

OOOOOO that looks shiney and new!

With the current (no pun intended, well maybe ½) broken set up, I could hear the engine note change when the alternator decided to start working. If I end up with a >35 Amp alternator I may have to think about which battery is getting charge untill the engine is warm but I doubt it. The MD11c is supposed to be 23 Hp, even allowing for it's age I still think we are overpowered.

I tend to cruise at 2000 rpm, about 5 knots. I have been known to go at 2500 rpm, and nearly 6 knots, but not often. 1500 rpm and 4 knots is much more relaxed.

[aquaplane]

It's working now, I found a loose connection around the big +ve terminal by wiggling bits until the warning light came on when the engine was stood which it wasn't.

[ash]

It's working now, I found a loose connection around the big +ve terminal by wiggling bits until the warning light came on when the engine was stood which it wasn't.

Good. You need to keep those nice new domestics happy.

Ash