85HP force prop modification question

[john from md]

I have a 1985 85hp Force with solid, non exhaust prop. My hub is a smaller diameter than the newer 1990's engines. Can I take a newer prop that has 15 splines (like mine) and mill the front down to fit my engine as a spare?

The newer props I believe have a 4.5 inch hub but the same pitch and and spline count as far as I can tell. They are thru exhaust types but that shouldn't matter. There are a few of these locally that can be had for $30. Obviously the larger hub will not enter my lower end and that is why I am asking the question.

I have a milling machine so cutting it down is not a problem. If I have too, I can also make thrust washers also.

Any suggestions would be appreciated.

Thanks,

John

 

[Frank Acampora]

Re: 85HP force prop modification question

The answer is a qualified yes. Since you do not have thru-hub exhaust it does not matter if the prop hub does not enter the gearcase like the stock one.

If I remember correctly, the thrust washer is the same diameter inside the prop hub so if the length of the rubber hub is the same, then it will fit your shaft. Only thing, the 4 1/2 hub will be wider than the Force gearcase adding a bit more drag. Some of the smaller Mercs (I think 80-90 hp) have the same sized hub diameter but the flange that enters the merc gearcase is larger than the Force internal diameter. These props will fit if you cut off the flange. I have a nice blue 13 X 21 test prop like this that I picked up for 25 bucks and when I get a "round tuit" I will modify it.

 

[john from md]

Re: 85HP force prop modification question

Thanks Frank. I don't care about the drag as I only want the prop for a "get me home" type of application. I don't want to spend $150 on a prop that will sit in my well for most of its lifetime.

Regards,

John