1990 Force outboard lower drive issue question

[gica]

I have twins on my boat initially I rebuild one motor and then noticed the second was full of water and rusted bearings so I replaced the front bearing and gear and the top bearing. I put it back and when I put it in gear at idle it would kill the engine. I took it apart and compared to the second drive when off the outboard and it did not spin freely as easy so I took off the thicker shims at the clutch and it did spin the same and play was similar at the prop. The issue with the turning off at idle persisted.
I rebuilt the second motor because it's really easy to do and that motor is perfect drives as it should.
When I use the boat I usually start it with the port good motor and only turn on the one that dies when at speed. They work great together.
The motor that dies at idle is set up with a little higher idle adjustment. It sometimes does not die especially when hot.
I did notice that that motor runs hotter than the other oneBoth motors were rebuilt the same way with all the wires redone and electronics new. Stator and triggers too.
Question:
Is the issue related to the lower drive not being shimmed by the book?
Is there an easy way to shim this drive?
I do have the manual and there are tools needed.The boat is a 24 footer Trophy 2302. It is a great boat for my needs. I have improved everything on it from the dash set up to gauge.
Buying newer engines and or boat not an option right now. Thanks in advance guys.

 

[Nordin]

I suppose you have the dual exhaust two piece drive shaft LU.
The problem with these are that there is no shimming spec. for the LU.
They were computer measured and the forward, reverse and pinion gears, prop shaft and drive shaft has a code with letters and numbers. The same for the gear housing.
Depending on code of gear housing the gears with shaft as a unit you have to matched it from a table (in the factory service manual).
I have rebuilt two or three of these units and I have use spec. from Chrysler late 70.es one piece gear housing and Mercury 70.es/early 80.es spec.
Do not know if it a good way to go but the only way I have found to go.
I do not know if those LU that I did that way have fail, but nobody have complained.

 

[jerryjerry05]

What are you using as a service book or manual??
They put out a Service Manual, Lower Unit 85-150 H.P. OB 4527 Issued in 9/89.
It covers rebuilding the lower units.
I think(not positive) all manuals printed after 1990 all Horse Power have this info in these manuals.
Over heating? get a temp gun and take readings along the head as it runs, compare to the other motor??
Make sure the thermo is the right one.

 

[Nordin]

Jerry I have the factory service manual OB4642 for 85, 90, 120 and 125Hp 1988 through 1991.
OB4643 for the 150Hp 1988 through 1991 and I have the OB4527 9/89 for LU 85-150Hp.
Shimming these LU is not the same steps as "regular" shimming with dial indicator as the older Chrysler one piece LU or Mercury LU form 70.es and 80.es.
Shimming these LU depends on what code the gear housing has and what code the forward gear assembly has.

 

[jerryjerry05]

Nordin, that's what the manual I have covers.
The newer coded gear cases.