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sailorboy1 · 31-03-2022, 13:14

Quote:

Originally Posted by Rumrace

Alternators use buckets of horse power. The older they get they use more. So the engine stalls because of load. It’s 18hp and the Alt prolly uses 5hp. So up the horse power so the diesel combustion is not staggered by the load.

Come on, do the math! My windlass is 50 amps. At 12v that is 0.8hp. My alternator is 100a, so 1.6hp.

bil56 · 31-03-2022, 13:37

what are the capacities of the batteries in Ah?

Timryl · 31-03-2022, 13:50

I had a similar problem where when using a stern thruster would stall a V10 MAN -thruster was wired to that start bank, and the bank was faulty. Replaced batteries - didn’t happen again.

GreenWave · 31-03-2022, 14:02

Quote:

Originally Posted by sailorboy1

You people saying you can stall your engine by loading your alternator have an issue! And if you can do it by operating your windlass and not trip its breaker you have another problem!

That too!

jeanathon · 31-03-2022, 14:34

Quote:

Originally Posted by sailorboy1

You people saying you can stall your engine by loading your alternator have an issue! And if you can do it by operating your windlass and not trip its breaker you have another problem!

The whole point of him starting this thread is that there is an issue, and he was hoping someone could help figure it out.

**Jim Cate** · 31-03-2022, 14:46

Well, one way to avoid the problem is to run the engine at higher rpm whilst using the windlass. We do that anyhow, just to keep the available voltage at the windlass a bit higher during loaded operation.

And perhaps just setting the idle speed a bit higher would do the trick!

Jim

bensolomon · 31-03-2022, 15:09

Your having a fuel delivery problem to the cylinders at low idle. This why at higher rpm, your engine doesn't quit. You have a 1998 hunter with original engine (I have a 1990). The anchor raises and lowers with engine off (load not a problem), and you stall when idling down to change gears.

Your lifter pump might be weak so that at low rpm, you don't draw enough fuel or your injectors are slightly clogged enough to restrict fuel at low rpm. Lastly, make sure your fuel cutoff goes all the way back to wide open after you pull. Sometimes, there is a little residual restriction left after engine shutdown due to cable wear.

The simplest is to do what Jim cate said: Idle at higher rpm or adjust your idle at the engine so you don't have to think about it. Also, do the simple stuff like checking your fuel shut off cable returns to wide open after you pull on it. It wouldn't be a bad idea to put on a new lifter pump for good measure since yours is old (I did that). The last thing to do would be to have the injectors cleaned, but that is more involved.

I am more concerned for you that this is a real safety issue. I could envision a scenario where you're trying to raise or lower anchor in a crowded anchorage in a stiff wind and having your engine quit could have devastating consequences. Or worse, waiting for a bridge opening and your engine stalls and you have to deal with that in close quarter navigation.

Full disclosure, I am not a diesel mechanic by any stretch. I am just an owner of a hunter around the same vintage of yours.

All the best,
Ben

HeywoodJ · 31-03-2022, 15:51

Quote:

Originally Posted by sailorboy1

Come on, do the math! My windlass is 50 amps. At 12v that is 0.8hp. My alternator is 100a, so 1.6hp.

I did do the math. You seem to have forgotten that alternators are not 100% efficient. Most are in the realm of 50% efficient, so yours takes 1.6 to 3.2HP from the engine. As posted, at the OP's idle the 2GM20 engine might be capable of 2HP. Electrical power loads up very rapidly. Dump an extra 50% load on the engine in electrical time without any additional fuel and presto - stall. Bigger engines generally don't have this issue, but the 2GM20 tops out at 16-18HP on a good day.

Quote:

Originally Posted by Jim Cate

Well, one way to avoid the problem is to run the engine at higher rpm whilst using the windlass. We do that anyhow, just to keep the available voltage at the windlass a bit higher during loaded operation.

And perhaps just setting the idle speed a bit higher would do the trick!

Jim

Exactly. Many operations manuals for boats with engine-windlass interlocks (I really dislike those, but they exist) recommend running in neutral at high idle or above to improve alternator output. This also reduces the chance of a stall.

David Mathis · 31-03-2022, 19:26

The short guess is that the 80 amp load of the windlass is being passed instantly to the alternator which loads the diesel. Any lag in the governor allows the engine to lose rpm and stall before the governor opens the injectors to compensate for the load.