Mercury Force History

Guys.... trying to clear up some misconceptions (maybe mine) regarding how much design change did Mercury influence Force when they took over until the phased them out. I always believed while Mercury made some changes including lower units, ignition etc. that the powerheads were indeed Force and not a Mercury design. At anytime did Mercury take one of their motors and put a Force badge on any of their models? Can someone like Frank A. clarify.

Thanks
Michael

Re: Mercury Force History

Force engine blocks remained West Bend/Chrysler design until Merc phased them out. Merc did change the mid and lower units to Merc design, and the crankshafts were re-splined to match Merc drive shafts.

The only blocks that Merc did meaningful changes on were the 70 and 75. Both these three cylinder engines were reworked with a single carb. Additionally, the 75 and the late '90s 90 hp were given long con rods and larger diameter wrist pins.

Re: Mercury Force History

Frank Acampora said:

Force engine blocks remained West Bend/Chrysler design until Merc phased them out. Merc did change the mid and lower units to Merc design, and the crankshafts were re-splined to match Merc drive shafts.

The only blocks that Merc did meaningful changes on were the 70 and 75. Both these three cylinder engines were reworked with a single carb. Additionally, the 75 and the late '90s 90 hp were given long con rods and larger diameter wrist pins.

Click to expand...

Damn you know your stuff!!!!

Re: Mercury Force History

Frank A , Since you are very well educated on Merc/Force engines I do have a question ... I have a 1994 90hp Sport jet , What engines have the same crank spline since I want more HP and performance ?

Re: Mercury Force History

I am good, but not great! You had to ask the one question to which I have no answer: I never worked on a jet drive Force.

Before we start though, reconsider. You do not have a lot of options. You can swap in a Force 120 or 125 block, or even a Chrysler 140--maybe.

Now, since a jet drive is only 75% as efficient as prop drive, any extra horsepower you swap in will be reduced by 25%. So even if you go whole hog,you can only expect maybe 4-5 MPH more. Now, if your engine is trashed, then it is worth getting the larger block. But otherwise, you are better off leaving it alone. AND: if you do swap in a bigger block, you still need to change the jet pump impeller to absorb the extra ponies.

NOW: IF and that's a big IF--If Merc did not change the splines on the jet drive crank, then, any Chrysler or early 90s Force 120, 125, 140 block will bolt up. And possibly the 5 cylinder 150--but then for sure you will need to "Massage" fiberglass

However they may have used a differently balanced crankshaft (like on the L-Drive, according to an old Chrysler mechanic)

All in all, If you want more performance it is really time to look for another boat.

Re: Mercury Force History

Thanks Frank , kinda of what I expected . Not worth it in the long run . My 90 is well tuned and runs like a champ . I just hate getting passed in the river by a boat with a 90 on it . I am limited to what I can get due to the tunnel I need to get out of from my canal.

Re: Mercury Force History

Sport jet cranks are different splines and totally different exhaust plate. To use a 4 cylunder engine you would neeed the matching exhaust.