Re: mercury 200 thunderbolt
Assume this is for the 20hp, I did not see the year I think.
Great motors, agree with above. One of the most popular Mercury made, right up there with the 4 cyl 50hp.
If from the seventies, couple of thoughts to look for:
*check the lower unit oil. the lower unit was the weak spot of the motor relatively speaking. You can bend the prop shaft if you run over enough snags, logs ect. This is likely true with any motor though.
*up until 74, the drive shaft was all carbon steel and so rusts. swap out to the ss shaft if possible. Or Grubbs makes a ss sleeve for the carbon steel drive shaft if you want to go that way.
*wiring tends to rot if original, the wires were a fine aluminum and corode over time.
Good luck!
