Lower Unit Compatability - 1989 Force 85

[RebelRidin]

Please bear with me. I have just purchased a boat with an 1989 85 HP Force that needs a lower unit. I do not yet have any shop manuals for it but would like to start looking for one. I understand that these units were made by Merc? Can anyone tell me the years and engine sizes for Force and Merc with lower units compatible with this 1989 Force 85 HP?<br /><br />Thanks for your time.<br /><br />George

 

[Realgun]

Re: Lower Unit Compatability - 1989 Force 85

Were going to need a bit more information such as model# on that motor. I beleive in 1989 they could have been the single exhaust or dual exhaust models. <br /><br />This means that the exhaust exited only from the snout-single or snout and through the prop-duel.<br /><br />Merc only updated the Force motors a bit in 89 after 91 they were more Merc that Force but were stil esentially the Chrysler design.<br /><br />And that design was not that bad.

 

[RebelRidin]

Re: Lower Unit Compatability - 1989 Force 85

Hi Admiral,<br /><br />Thanks for the reply and the info. I guess I've been spoiled by my experience with Johnsons and Evinrudes. A lot of times there it was easier to just remember when changes were made. <br /><br />I believe this is a single exhaust through the snout on this Force. I will be picking the boat up on Monday and I'll have to get back with more info. <br /><br />I was afraid I had gotten into a area of confusion when I heard that was about the time Merc took them over. With model number in hand it shouldn't be any problem ordering new parts but when looking for used items it sounds like this could be a pain.<br /><br />Until later, thanks again.<br /><br />George

 

[phonedrn8]

Re: Lower Unit Compatability - 1989 Force 85

is there ny update to this?
I have the same issue looking to replace my L/U on my force 85.
looks like i need to replace mine prev owner tried to drive his enging on the road or desert some thing like that need replaced

 

[Frank Acampora]

Re: Lower Unit Compatability - 1989 Force 85

The same lower unit with VERY MINOR changes, was used on all Chrysler 3 and 4 cylinder engines from late '79 --say '80 right through Force '89. Although Merc started making changes in 1990 (two piece drive shaft and slightly different water pump) That same lower unit will fit the 1990 3 and 4 cylinder Force with possibly the exception of the 3 cylinder 70 HP.

Engines: ALL 75 through 140 HP.

The only major difference was that some 85HP and 90 HP engines had 2-1 gearing instead of 1.78-1. Not sure about 75s. So if your engine has 2-1 gearing and you use a 1.78-1 lower unit, you will notice a loss in performance to the tune of 3-5 MPH.

So in summation, As long as you check the gear ratio, You can use the late Chrysler 1 piece lower unit, the early white Force 1 piece lower unit, or the Dark Force (NO, not Star Wars) up to '90 and possibly as late as '92 lower unit. Not sure the exact year Merc went to the Merc midleg and lower unit--but it was later than '90, of that I am certain. Single and dual exhaust are interchangeable; that is, the bolt pattern is the same. However, there may be an extra sleeve inside the midleg and of course, you must use a thru hub propeller.
I prefer the single though.

NOTE: It is quite acceptable and even preferable to use a 2-1 gear ratio to replace a 1.78 to 1 ratio. Just get a prop with 2 inches more pitch. For example: if you have a prop with a 17 pitch, use a prop with 19 pitch. You will notice a gain in speed.