Engine stalls when raising or lowering anchor

[Building a boat]

Hello,
I have a weird issue which has me and the mechanic and several people I have asked stumped.
I have a 1998 Hunter 310, it has the original Yanmar 2GM20F 18hp motor in it. 2400hrs on motor. I have a single cranking battery for starting and 2 6 volt batteries for the house.
Anchor is wired to run off the house bank.

Issue is whenever I go to use the anchor, if the engine is only idling the engine stalls. Normal idle on tac is about 1000RPM, set by mechanic. I can rev engine up and use anchor, but slow down to change gear it stalls, so slowly down from a fast reverse or forward and engine stalls if still letting out or raising.

When engine stalls, it starts up right away, no hesitation, no smoking, runs perfect heat at full revs for long periods. Mechanic says engine is running great and I kinda agree.

I did some voltage tests with smart meter.
engine running - batteries at 14.2 v. When I raise anchor (rated to draw 80amps)
1600rpm, 20amp draw from batteries, alternator supplies 55amps
1200rpm 35-40 amp draw from batteries
1000rpm 55 - 80 amp draw from batteries. Engine stalls.
We just redid governer, all springs and such, cleaned air filter. Have redone fuel filters twice.
Anchor raises and lowers fine with motor off.

Ideas ????????

[Uncle Bob]

Originally Posted by Building a boat

Hello,
I have a weird issue which has me and the mechanic and several people I have asked stumped.
I have a 1998 Hunter 310, it has the original Yanmar 2GM20F 18hp motor in it. 2400hrs on motor. I have a single cranking battery for starting and 2 6 volt batteries for the house.
Anchor is wired to run off the house bank.

Issue is whenever I go to use the anchor, if the engine is only idling the engine stalls. Normal idle on tac is about 1000RPM, set by mechanic. I can rev engine up and use anchor, but slow down to change gear it stalls, so slowly down from a fast reverse or forward and engine stalls if still letting out or raising.

When engine stalls, it starts up right away, no hesitation, no smoking, runs perfect heat at full revs for long periods. Mechanic says engine is running great and I kinda agree.

I did some voltage tests with smart meter.
engine running - batteries at 14.2 v. When I raise anchor (rated to draw 80amps)
1600rpm, 20amp draw from batteries, alternator supplies 55amps
1200rpm 35-40 amp draw from batteries
1000rpm 55 - 80 amp draw from batteries. Engine stalls.
We just redid governer, all springs and such, cleaned air filter. Have redone fuel filters twice.
Anchor raises and lowers fine with motor off.

Ideas ????????

My take on it would be the windlass is drawing more than the alternator is producing at idle, loading it up and causing the engine to stall. Is the windlass wired to the start or house batteries, is the alt wired to the start or house batteries and how is the other battery wired for charging.

[Building a boat]

I will chase wire ng down , may take me a couple weeks. Other problems :0)

[Building a boat]

Managed to quick check, windlass is connected right to house bank so alternator is behind. Checking on other battery

[jeanathon]

I agree with Uncle Bob. Try using the windlass with your battery selector set to isolate the different banks to see if it makes a difference. A side note I am surprised it would draw so much while letting chain out...

[Antares]

A couple of questions on this mystery. What is the voltage when the windlass is operating? How much does it drop? Also what is the amp output of the alternator? I can see a circumstance where the windlass causes a significant voltage drop and then a large alternator kicks in and overpowers the engine at idle rpms. At higher rpms the engine is making enough power to keep up with the alternator demands.

I've seen similar sized diesels stopped at idle by a large alternator coming online quickly.

[sailorboy1]

Well the windlass load, acturally any electrical load should have no effect on a diesel engine running. The only thing that can make the engine just stop is loss of air or power and that windlass load is not enough to stall the diesel!

So ........................ do you an electrical fuel booster pump?

[Rumrace]

Windlass are power pigs. Can eat a whole 100Amp battery. It’s really hard on you’re alternator which are often designed to peak at twice the rpm your engine will run at. 1800-2000 rpm may solve it but as windlass motors get old they use more juice.
Most times swapping out the motor and even old relays can dramatically reduce the demand.

[Cheechako]

You might have a bad battery, only holding a surface charge, which then allows the windlass to require the alternator to go to maximum when you use the windlass. (or it could be battery or cable connections are dirty)
The little 2 cyl Yanmar has little HP at idle.
The windlass SHOULD work off a single battery fine for normal anchoring. (Many large boats just use a battery in the bow)

[Sam Woodbridge]

Have you considered that your engine might have low compression? Once the windlass engages it puts such a load on the alternator that the engine stops because it’s weak?

Just my two cents and I’m no machanic!

[NYSail]

Older Diesels don’t need power after they start. They are compression based. Start and remove batteries alt etc…… and engine will run. Unless someone put in a dedicated electric fuel pump and removed stock fuel pump.

[Cheechako]

Originally Posted by sailorboy1

Well the windlass load, acturally any electrical load should have no effect on a diesel engine running. The only thing that can make the engine just stop is loss of air or power and that windlass load is not enough to stall the diesel!

So ........................ do you an electrical fuel booster pump?

Nah, I have stopped a 6 hp Kubota diesel running at low rpm with a big load on the alternator several times. Too much HP required for not enough HP in the engine.

[HeywoodJ]

I second or third the idea that the alternator is loading up and stalling the engine. You say at 1000 RPM the batteries provide 55-80A, which means at the low end the alternator could still be providing 25A. That's half a horsepower output, which means 1HP input for most alternators.

According to the power curve for the 2GM20 (conveniently posted by Wottie) the engine is probably only producing 2HP total at that speed, and the engine itself needs most of that to keep itself going.

To test, disconnect the house bank so that it cannot charge in any way from the engine/alternator/start battery. Run engine and windlass and see what happens.

[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.

[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!