Will a 1989 115hp powerhead swap to my 1993 90hp lower unit?

[93nitro]

Been having a time trying to find a replacement motor. Can someone please let me know if this setup will bolt together and work. What problems will this cause, if any?

 

[Frank Acampora]

Re: Will a 1989 115hp powerhead swap to my 1993 90hp lower unit?

That is a difficult question because right around that time, 1993, Mercury started monkeying around with things.

Physically, the 4 cylinder block will mount in the same way as the three cylinder 90. HOWEVER: There is a possibility that Merc changed the crankshaft splines. If you have the option, count your 90 HP drive shaft splines and the 1989 crankshaft splines. Obviously, the 4 cylinder block is taller and you will need a bigger hood to cover it. While the electrical system is similar, you will need a 4 cylinder trigger and another coil unless the four cylinder block is complete with ignition.

AND---If the 1993 has Merc control cables, you may need to jury rig them on the 1989 or buy an earlier US Marine control box and cables. If you have the option, examine and compare both blocks before starting.

Lastly, did Force Make a 115 in 1989? I thought they only made 120 and 125 in the 4 cylinder engines

 

[93nitro]

Re: Will a 1989 115hp powerhead swap to my 1993 90hp lower unit?

I had a guy e-mail me and said he had an 89 115 Merc and maybe I just assumed it was a force. I might be a little under-informed here but did they make a mercury force, and a mercury line at the same time? Is the spline and hood all I have to worry about? I looked up some stuff on them online and it says both motors have a 15 spline shaft. He said he blew the lower unit so all up top should be good.

 

[Frank Acampora]

Re: Will a 1989 115hp powerhead swap to my 1993 90hp lower unit?

Mercury did buy or was bought by AMF Brunswick and during the kater years of the Force brand did make Force engines. Some people do refer to them as Mercury Force or even Mercury. The truth is that Mercury kept most of the original design and made modifications in small increments. Almost nothing on a Force engine is swappable with either a Mercury or Mariner engine.

If the engine is indeed a 115, it is most likely a "Tower of Power" inline Mercury six cylinder. Before you buy, write back for further clarification because there is almost no way to mount this block on your leg.

 

[93nitro]

Re: Will a 1989 115hp powerhead swap to my 1993 90hp lower unit?

Ok thanks a million for the info. If I get close to buying it I will for sure check back with you to see what we are dealing with.
Thanks again for the help!