How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

[capnstabbin]

How to replace exhaust gasket in 1998 75 HP Mercury/Force Tracker

Does anyone now hoe difficult it is?

I have oily/milky exhaust water

 

[Frank Acampora]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

It is not tremendously difficult unless you have stubborn bolts. It is relatively common to snap at least one bolt head off when removing them. I would expect less problems from a 1998 than from an engine in the 70s or 80s, unless it is a salt water engine.

When reinstalling, torque to 70 INCH pounds

 

[capnstabbin]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

Does the bottom part of the "pan" come off to do so, does the power head have to come off?

 

[Frank Acampora]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

You certainly do not need to remove the powerhead. The bottom of the cowl does not need to be removed unless you have no clearance for a wrench. The block is basically the same as any three cylinder Force so while I have removed a block for rebuilding, I forgot if there is enough clearance.

Anyway, you remove all the bolts and carefully pry out the cover. It just sits on the surface of the block, no protrusions stick inside. The gaskets will be destroyed because they are self gluing from the factory. There is a stainless plate andwiched between two gaskets, the cover plate, and the block. SO; Once you pry off the cover see if you need one or two gaskets.

The gasket between the stainless plate and the aluminum cover will only leak to the outside of the block SO: Usually the leaking gasket is the inside one. Thus: if the stainless plate does not separate from the cover, then you will only need one.

 

[capnstabbin]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

 

[Frank Acampora]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

Ahh! Cap'n---before you go replacing the exhaust cover gasket, check the lower unit seals. It is more likely to one of them than the exhaust cover plate gaskets.

Remove the prop first and see if oil is leaking out around the prop shaft. If that is clean, then drop the lower unit and check the shift rod seal. If that is OK, then remove the water pump and check the drive shaft seal.

I suspect that you will find the prop shaft seal leaking though.

 

[capnstabbin]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

OK, what if there is oil on the prop shaft before I droop the lower unit.

And is this a big deal, also before I drop the lower unit, do I just disconnect the shift rod linkage? or is there more to disconnect before I drop it?

I have few guys I am in contact with who are helping me also with this motor, is it all worth it, I dont have an expensive boat, with that said, I would not put a new $6000 yamaha motor on it, and with that said I dont want to spend more than $1000 to fix this one.

Is it all worth it?

 

[Frank Acampora]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

If there is oil leaking oil the drive shaft seal, there is no need to drop the lower unit. Drain the oil. You remove the prop then remove the anode behind it. Underneath you will see four bolts. You remove them. Notice the O rings under the washers--better to replace them too. Now, using a couple of pieces of threaded rod, thread into the two holes that were holding the anode. Make a plate or whatever and using the threaded rods, pull out the spool with the prop shaft seal. Replace the seal (around 20 bucks) and replace the spool being sure to line up the four bolt holes. replace the four bolts with new O rings under the washers and tighten. refill case with oil. Go have fun.

 

[capnstabbin]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

OK, that does not sound that hard, maybe. I also have this set of photos of the spark plugs, these plugs are brand new and just run for a 10-15 minutes on land, on ear muffs and in a bucket.



The top one looked the worst (dirtiest / oily) and and that cylinder measured over 120 on compression test
The middle one looked the best (cleanest not oily) and measured around 120 on compression test
The bottom one looked dirty but not as bad as the top one and measured around 115 on compression test.

I know I am removing the lower unit, I know thats where the oil is coming from, I removed the drain plug, it was milky, the same color thats coming out of the prop after testing at idle, and in gear in a bucket, it starts to drip from the prop as shown in this photo


The same color oily stuff seams to be on the plugs shown on the photos of these plugs above.

 

[Frank Acampora]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

I forgot that that was a 75 with the Merc lower unit and gave instructions for earlier lower units. Disregard!

The oil does indeed appear to be lower unit oil and most likely it is from the prop shaft seal. You can see the seal behind the prop thrust washer. No need to remove the lower unit. Remove the prop and remove the two allen head bolts holding the bearing carrier. tap it gently to rotate it a bit then using a wood block alternately tap on each ear to pop out the carrier--That's all it takes. The carrier is long and has the rear bearing and seal. It will also be coated in exhaust it is a thru-prop exhaust unit.
While you are replacing the seal, also replace the O ring at the back of the carrier. This seals the carrier to the case and keeps oil in the lower unit.
Total time if it doesn't fight you should be about 1/2 hour.

None of the plugs looks bad and any accumulation you see will be from oil in the fuel.

 

[capnstabbin]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

Thats good news and sounds easy enough, I am still taking the lower unit off as I still need to do the water pump and I want to check other seals or signs of other leaks, any suggestions or tips, what else should I look for?

 

[Frank Acampora]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

It is a Mercury lower unit but it has a push-pull shift rather than splined rotary, so you need to disconnect the shift rod. I have one downstairs but I am not dressed and don't remember how the shift rods are joined. But, I do remember that it was not difficult to separate them. I also don't remember exactly but there may be a hidden bolt under the trim tab. If yours had a speedometer impact hole, then the rubber tube between the leg and transom also needs to be disconnected. Stainless steel Mercury water pump body--never goes bad so you only need the impeller and special Mercury impeller key--don't lose it. Water pump bolts usually don't corrode into the case so they will usually not give much trouble in removing.

 

[capnstabbin]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

Frank, you're awesome!!!!! Wish me luck.

I'll start a new thread with more photos once the lower unit is down.

Put a fork in this one.

 

[terryjp]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

i have 1998 75hp force need to repace seals had water in lower unit is there a step by step directions anywhere thanks terry

 

[capnstabbin]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

I am currently in the process of re-doing the seals for the lower unit on this thread here

http://forums.iboats.com/showthread.php?t=465842&p=3150480

Read all and memorize the posts from Frank Acampora

 

[capnstabbin]

Re: How to replace exahaust gasket in 1998 75 HP Mercury/Force Tracker

Here's mine after a long winter, maybe even longer, this is the 1st year I owned it not sure how long it sat, but its a lot quieter than my old '76 Johnson 70 HP Seawhore.
http://www.youtube.com/watch?v=kxfGe2ZEQ2A