How much end play in lower unit Force 85?

[capri1600]

I have a white 1983 Force 85. I seem to have about 1/4" of endplay at the prop. That is, the prop shaft will push/pull fore and aft about 1/4". How much is too much and what can be done to reduce the play if this is too much? My white Force 125 has maybe an 1/8th of an inch play.

Marty
http://www.martyhammersmith.com

 

[Frank Acampora]

Re: How much end play in lower unit Force 85?

Both are too much! The end play or in and out movement of the propeller shaft should be about .006 to.010.

Do not confuse end play with an improperly mounted propeller. Some props require a spacer behind the nut and washer because the shaft splines are longer than the prop hub. Without this spacer, the prop will slide on the shaft somewhere around 1/8 to 1/4 inch. Sound familiar?

 

[capri1600]

Re: How much end play in lower unit Force 85?

The prop is not sliding on the shaft. The shaft and prop, solidly together, are moving fore and aft in the housing.

Both are too much! The end play or in and out movement of the propeller shaft should be about .006 to.010.

Do not confuse end play with an improperly mounted propeller. Some props require a spacer behind the nut and washer because the shaft splines are longer than the prop hub. Without this spacer, the prop will slide on the shaft somewhere around 1/8 to 1/4 inch. Sound familiar?

 

[TwoFish]

Re: How much end play in lower unit Force 85?

I have a 1998 75 Force which is doing the same .028.

Does this mean the gearbox needs to be reshimmed?

 

[Frank Acampora]

Re: How much end play in lower unit Force 85?

Capri: This is difficult to describe. Inside the lower unit, there is a shim ON the forward gear (in the center and over the prop shaft) which sets the end play. This shim is usually about .054 or so but can be quite a bit thicker depending upon the individual case and gear set.

In reverse, the shaft has a land on it which rides against the center of the reverse gear.

IF the shim is missing or if the land and center of the reverse gear is worn, or if both conditions exist, the end play will be excessive.

Coupled with that, the reverse gear is carried in an aluminum slug with a center needle bearing and a face thrust bearing with a hardened steel thrust plate. IF the thrust plate is missing, then end play will be excessive and in reverse, the thrust bearing rollers will wear the aluminum slug. The reverse gear will also not be in proper mesh with the pinion and the teeth will wear or break.

SO: the question becomes: Has anyone worked on the lower unit before or after you acquired it and do you trust them?

Excessive end play is a difficult call because it does not affect performance in forward gear, so it is difficult to say whether or not you need to disassemble the lower unit to find the reason. However, if you have the time It might be a good thing to check. It will only cost you the oil change (which you would do periodically anyway) and some time.

Twofish: As far as the .028, I don't know the specs on the 98 lower unit so can not answer you. You need to start a new thread about that question.

 

[capri1600]

Re: How much end play in lower unit Force 85?

Ok, I got a little more serious and precise about the endplay in the propshaft of my 1983 Force 85. It is actually about .094. A little looks like a lot I guess.

Marty

 

[capri1600]

Re: How much end play in lower unit Force 85?

Excessive end play is a difficult call because it does not affect performance in forward gear, so it is difficult to say whether or not you need to disassemble the lower unit to find the reason. However, if you have the time It might be a good thing to check. It will only cost you the oil change (which you would do periodically anyway) and some time.

Yeah, It'll be coming off for an impeller inspection/replacement this Winter and the Amsoil synthetic oil is coming out too. In regards to anyone working on the lower unit, I would have no idea. I bought it on the back of a Bayliner project boat about 5 years ago and only started using the motor a couple weeks ago. It's a 1983 model and who knows if this is even the original lower unit. It runs fantastic and shifts smoothly though. I had the lower unit out last year when I installed a complete water pump kit and I also drained and refilled the oil with the Amsoil synthetic. The oil that came out looked clean but not brand new and I don't recall any appreciable amount of filings. I would be sensitive to this as I am also an aircraft owner and we always sift through the old oil and filter to ID anything that might be wearing.
I am mechanically inclined so I'm not opposed to getting into the lower unit.

Marty
http://www.martyhammersmith.com

 

[capri1600]

Re: How much end play in lower unit Force 85?

Hey Frank, what do you think about .094 play. Do I need to tear into this?

Marty
http://www.martyhammersmith.com

 

[Frank Acampora]

Re: How much end play in lower unit Force 85?

Since it really only involves removing the four bolts that hold the spool in and the two semi circular clips that hold in the slug, it's worth investigating.

It is not quite as easy as I am making it sound: First the anode must be removed. Some times the spool is corroded into the case and pulling it takes a considerable amount of effort. This may very likely be the scenario if it has been used in salt or if it has never been removed before.

And of course, after you remove the reverse gear and prop shaft assembly, you will need to replace the shifter saddle which will fall off, but these are time consuming, not difficult.

On the plus side, you will not need to re-shim the gearpac since you will not be removing the forward gear and pinion. Current shimming will probably be correct as it will not affect end play and if it were incorrect, you would have already destroyed the gears.

So, my vote would be to disassemble when you have the time.