Yanmar 4JH57 - Battery Voltage Too High

[Pstofberg]

Hi everyone,

I hope someone can help. Today, while motoring down a narrow channel, we got our prop fouled on a line/rope in the water. I dived and untangled the rope which was fortunately not too tightly wrapped around the prop.

However, when I started the engine again, The engine controls started emitting a high pitches warning sound and showing the message “bT VOLT” which, according to the Yanmar operations manual means “Battery Voltage Too High”.

Does anyone know if this is something I can fix or should I get expert help? Am I looking at a possible haul out? (I really hope not!!) Other than the warning sound the engine sounds fine. It did cut out at one point while docking, but started again without any problem.

I’ll greatly appreciate any advice!

[Privilege]

You seem to have two separate issues here. Firstly, what sort of drive do you have on your Yanmar? Is it a saildrive? If so, there seems to be a good possibility that you have sheared the prop. The saildrive props have a bushing, often rubber which shear when the prop is forced to stop. It is better that you lose a prop than a gearbox. From looking at the prop it is often hard to tell that you have sheared them as there is sufficient left inside to turn it without a load but when the boat is under load the prop will spin on the spindle. This could lead to your engine over-revving and possible an increase in the alternator output....however, I cannot see any realistic correlation between any damage to the engine/prop and the alternator putting out excessive voltage. You will have to put a voltage meter on your alternator output.