Re: Engine Swap Merc/Force
NO! Although Mercury Bought the Force line and later put their lower units on the engines, The Mercury and Force blocks have different mounting patterns and will not swap with each other. NOW: I could not tell from the photo, but on the outboards Later Force used a special match plate to mount the force block to the Merc midleg. Thus, If there is a match plate on your jet drive it MAY-- but it is unlikely--may just be possible to swap in a Merc block. This would take a bit of "massaging" though. More fuss than it would be worth.
Depending upon year, Mercury did change the number of splines in the crankshaft SO: You can swap in almost any Force 3 or 4 cylinder block IF the crankshaft splines are the same.
Cute little James Bond type boat.
Force did make a 5 cylinder 150 (that's the largest they ever made) and that block could be swapped in if the jet pump has the old number of splines. But, it will be about 6 inches taller and you most likely would need to do some cutting of the hull to make it fit. Also, you would need a complete block with electronic ignition since it is 5 not 4 cylinders. Again, possibly more fuss than it is worth.
Now, remember: the jet pump is sized to accomodate the 120. Any sizeable increase or decrease in power will require a change of impeller--and I don't know if there are aftermarket parts for these units. If the engine is running well, stick with what you have and be satisfied. That little squirter will probably do a good solid 50.
I went back and looked at the engine again. There is a special exhaust adapter on the block. Without making another different one, no other block will easily swap in. Again, if the engine is running, stick with what you have.
