Need help identifying Mercury motor

bkeys · Oct 6, 2012

I recently purchased a Mercury 40 Thunderbolt 4hp outboard. The serial number is 2200771. There is no year numbers under the serial number and all of the sites I've found do not include that serial number range. Any idea what year the motor is??

Dave1027 · Oct 6, 2012

Re: Need help identifying Mercury motor

Is it a 1 cylinder or 2? Post a pic.

Laddies · Oct 6, 2012

Re: Need help identifying Mercury motor

That serial number is for a 1967 3.9 HP is it possible that someone just put a 40 bonnet on it? A 4HP thunderbolt has a coil right above the sparkplug and a 39 the coil is under the flywheel.

bkeys · Oct 7, 2012

Re: Need help identifying Mercury motor

It is a one cylinder. I'll try and get a picture posted. I was wondering if somebody changed the cowl...but was also wondering if somebody changed the serial number tag. Thanks for giving me some more to go by. I got it for $60.00 from a guy and don't even know if it runs. I figure first step is getting a manual and schematics.

bkeys · Oct 8, 2012

Re: Need help identifying Mercury motor

Here are the pics

Laddies · Oct 8, 2012

Re: Need help identifying Mercury motor

Someone has installed a later model 4HP powerhead on a 3.9 HP torque tube and lower unit I believe, check on the area above the exhaust plate of where the crankcases bolt together for a different serial number. If that don't work we can come close with the carb model and look up under the flywheel at the type of stator the engine has.

Chinewalker · Oct 9, 2012

Re: Need help identifying Mercury motor

Hi think someone has changed out the swivel bracket as the motor appears to match the cowling. Look for a 7 digit number stamped in the cylinder block. It won't be a cast number - it WILL be stamped, much like the number on the tag.

bkeys · Oct 9, 2012

Re: Need help identifying Mercury motor

I found 3656012 stamped on the side of the cylinder case

Chinewalker · Oct 9, 2012

Re: Need help identifying Mercury motor

That's your "real" serial number. Your motor is a 1973, which gibes with the external coil and the cowling decals...

bkeys · Oct 10, 2012

Re: Need help identifying Mercury motor

Thank you for the help. I'll see what I can do to get a manual for it now. Also...since I have no idea what I really have here....$60.00 shot in the dark and all....is there a compatibility issue with the '67 lower unit and the '73 powerhead or will they play together just fine?

Chinewalker · Oct 11, 2012

Re: Need help identifying Mercury motor

Mercury played some games with their mids and lowers during that period. Earlier ones had a full-length shift rod that extended up into the belly pan, while others had a splined coupling below the swivel bracket. Earlier mids also had a shorter "snout" at the rear of the leg where it meets up with the gearcase, with the mating gearcase also have a shorter top surface to match. I believe, but am not 100% certain, the '67 will have the short, and the '73 will have the long. You can tell by looking as the "short" will have the AV plate extending about an inch beyond the rear of top surface the gearcase housing, while the "long" will have the AV plate about flush with the rear of the top surface of the housing. These pics should illustrate what I mean.

Need help identifying Mercury motor

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