Help with Merc 20hp ML model year

[wdm2]

Just bought an older 20hp manual tiller Merc outboard. This engine is made in Ontorio Canada, so it has a Canadian sr# as follows 7159962 it also says thunderbolt ignition on the cover. Best I can tell from the sites I looked at to try to match the serial number is that its a 1981-83. If anyone can help with any more accurate info on this engines actual year it would be appriciated. If more info is needed I will try to find it on the power head. Thanks. Walt.

 

[achris]

Re: Help with Merc 20hp ML model year

1980.... Model number 1020200... and it's a short-shaft...

 

[wdm2]

Re: Help with Merc 20hp ML model year

1980.... Model number 1020200... and it's a short-shaft...

Thanks for that info achris. I started that 20hp merc today ran fine after over an hour of remove the grime on the block, and replacing the plugs,and cleaning the fuel filter. However it appears to need at least a new impeller, very little water coming out of the discharge hose, and hose lines not blocked. Bought new impeller today, will try to takcle replacing the impeller tomorrow or the next day. I have done a couple of omc, and one yamaha water pumps, but never a merc.
Any hints you could offer to make job easier would again be appreciated. I have a mercury manual that I borrowed from a friend, but it only covers 45hp and up, not sure if there is allot of difference between a two cylinder and three cylinder model as far as the water pump goes. Thanks again.....Walt.