Mercury 500 siezed

[56north]

Hi, I have just bought a '73 Mercury 500 (kindly dated by a memeber of i-boats) I bought it blind from ebay as 'spares or repair' and it was said to be listed as such as the seller hadn't run it for a while and wasn't sure it would start. A friend of mine collected the engine from a long way away so I didn't get a chance to view it until it was actually in my hands.
The first thing I've discovered is that it is siezed. I tried to turn the propellor with it in gear but it wouldn't budge, even when I took the plugs out.
I have had it on its back now for a couple of days having poured some penetrating lubricant down each barrel but it still isn't shifting. I don't know if this engine was last used in salt of fresh water.
My questions are -

are mercury's (or any 2 stroke outboard for that matter) known to sieze easily if left for some time?

Could it be siezed in another area than the pistons i.e could it be the drive shaft from the propellor that's siezed.

Is there any way of 'easing' the pistons by turning the flywheel with a wrench?

Am I being impatient and should I expect it to take alot longer to unsieze.

Any advice in how to deal with this problem would be hugely appreciated. - thank you in advance.

 

[RogersJetboat454]

Re: Mercury 500 siezed

You're trying to turn over your motor from the entirely wrong end. Put a wrench on the flywheel nut, and see if it moves with no more then a reasonable amount of force. If it still won't budge, then pull the lower unit and repeat. If it spins with the lower unit out of the picture, then you have problems in the lower unit. If it is tight or still refuses to budge, start pulling it apart. You should get your self a factory service manual if you are serious about bringing this back to life.

 

[56north]

Re: Mercury 500 siezed

Many thanks for the advice. I was aware that I should be turning the motor over from the flywheel end and my next move was going to be to remove the pull start mechanism and try that. Am I not correct in thinking ,that if it wasn't seized , I should be able to turn the motor over by turning the prop' by hand especially if the plugs are removed? Or is it the case that there is a lot more torque, than I imagine, in four cylinders? I'm new to outboards - more used to single cylinder, 2 stroke bikes.

 

[Mi duckdown]

Re: Mercury 500 siezed

North. Do what Rogers said. ok? don't over think it. that would be like starting your truck by spinning the wheels in gear.???

 

[RogersJetboat454]

Re: Mercury 500 siezed

Many thanks for the advice. I was aware that I should be turning the motor over from the flywheel end and my next move was going to be to remove the pull start mechanism and try that. Am I not correct in thinking ,that if it wasn't seized , I should be able to turn the motor over by turning the prop' by hand especially if the plugs are removed? Or is it the case that there is a lot more torque, than I imagine, in four cylinders? I'm new to outboards - more used to single cylinder, 2 stroke bikes.

Might be able to pull that off with a smaller motor, or even your motor if it was in top shape, but it's the Rube Goldberg way of doing things, and will make spinning the engine over that much more difficult . Pull the rope starter off, and put a socket and breaker bar on the flywheel nut. If it doesn't break free with little force, pull the lower and repeat...

 

[56north]

Re: Mercury 500 siezed

Thanks everyone - as you said, I've managed to free it up with socket on the flywheel. Need to get a fuel line fitting and fingers crossed she goes! I've since heard that mercury 500's, pre '76, are prone to transmission problems because of a steel drive shaft which can rust. Hopefully that won't be the next problem! Many thanks again - this is a great site!