Replacing transom seal on a 1985 3.8 omc

Status
Not open for further replies.

Newbie@boats

Chief Petty Officer
Joined
Apr 6, 2010
Messages
536
I just bought the boat. Everything works but the transom seal is shot.

How hard is it to change out? Does the out drive have to come off? The guy took the old one off with out taking the outdrive off and didnt damage it...

I paid 300$ for the boat and trailer, and besides the broken windshield its actually in great shape.

Thnaks!
 

mrlassi1

Petty Officer 3rd Class
Joined
Aug 30, 2009
Messages
97
Re: Replacing transom seal on a 1985 3.8 omc

Although my OMC is a 1976 model it may not a lot different than yours. I replaced mine during a complete rebuild last year.

Remove the upper/lower drive (leg). On my stringer unit this takes about 15 minutes. Can't advise about yours. I don't think you will be able to get the new seal over the drive otherwise. I guess you could always cut the old seal away withouth having to work it over the leg. So, once you have leg removed. Remove the screws connecting the seal to the transom. Remove the outer seal aluminum support ring from the seal. Now is a good time to clean that ring up and put a fresh coat of paint on it. Rustoleum appliance epoxy (black) does a nice job.

With the ring removed. Peel back the outer edges until the seal is loose all the way around. A putty knife may help. Once the seal is free, pull it back away from the transom to expose the stainless steel band securing the inner lip of the seal to the intermediate drive. This band is on the transom side of the seal. It is the same type of clamp you've seen used on radiator hoses - just much larger in diameter. Once the clamp is loose you can slip it off the tansom seal and leave it hanging on the intermediate drive.

Make sure you buy the correct seal. There are a different number of screw holes around the perimeter of them. Count yours and make sure the one you are buying has the same number.

Make sure you clean the seal contact area on the transom. I used lacquer thinner and a scotchbrite pad. A narrow bead of yellow contact cement was used on mine and it's tough to get clean.

Slip the new seal over the intermediate drive making sure you pay attention to the "top" orientation on the seal. Install the inner seal clamp. Install the outer seal support ring. Add a narrow bead of weather stripping adhesive on the transom surface around the perimeter of the outer seal. Put a dab of silcone sealant in each screw hole and install the screws around the outer perimeter. Tighten each screw a little and go all the way around until they are all snug.

Reinstall your drive leg. Let it dry overnight and test for leaks.
 

Newbie@boats

Chief Petty Officer
Joined
Apr 6, 2010
Messages
536
Re: Replacing transom seal on a 1985 3.8 omc

Great thanks!

So thats basically like im doing the impeller in the bottom end of the outdrive take that half off?

On my old merc's I have taken that off before so I am pretty comfortable with doing that.

I have the 22 hole. I will go to my local marina tomorrow and have them order it for me.

I just wanted to make sure it ran and everything worked before I bought it...outdrive engages, trim and tilt works, motor runs great and does not over heat.
 

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
Re: Replacing transom seal on a 1985 3.8 omc

Great thanks!

So thats basically like im doing the impeller in the bottom end of the outdrive take that half off? On my old merc's

not even remotely similar to a merc - the lower unit steers around the upper of an OMC stringer...the shift cable snakes through the upper and you either remove the whole outdrive (get a factory manual to see how to disconnect your shift cable- need to be careful - it's over $600 for a cable), or use lots of hot soapy water and you can carefully work the boot over the drive with the prop and trim tab/anode and water directors removed.
 

Newbie@boats

Chief Petty Officer
Joined
Apr 6, 2010
Messages
536
Re: Replacing transom seal on a 1985 3.8 omc

Yes, I have been reading around online and it seems a few people actaully snake it around the outdrive with hot and soapy water...

I will go order one today at the marina, and then start preping the transom,...

"prop and trim tab/anode and water directors removed"

Can you explain what thoes are, prop I know and I will remove it....trim tab anode and water directors?
 

Newbie@boats

Chief Petty Officer
Joined
Apr 6, 2010
Messages
536
Re: Replacing transom seal on a 1985 3.8 omc

Quick question, I ordered the seal off eBay. Almost half the price from the dealer.

How do I prep the transom to seal it properly? Where can I get the silicone type sealer?
 

Charliemike 06

Recruit
Joined
Apr 18, 2011
Messages
3
Re: Replacing transom seal on a 1985 3.8 omc

I'm in the process of replacing my transom seals as well on a 1983 3.8L Searay. Unfortunately, the rings were bad as well and would not fit over the outdrive, so the drives had to come completely off. Getting the shift cable back through he channels and hooked up correctly is a real pain in the bass! 3M 5200 Marine sealant (West Marine $12.99) really did the trick as far as sealing everything up.
 

Newbie@boats

Chief Petty Officer
Joined
Apr 6, 2010
Messages
536
Re: Replacing transom seal on a 1985 3.8 omc

Ahh sorry to hear that, mine is still good, and all the screws are accounted for.

I ordered the seal and it should be here by this weekend, the thing I am worried about is since the boat sat for about a year and a half before I salvaged it, the seal was off I hope when I put the screws in they thread in right and the wood is not rotted out even though its appearing pretty solid
 

Newbie@boats

Chief Petty Officer
Joined
Apr 6, 2010
Messages
536
Re: Replacing transom seal on a 1985 3.8 omc

Well I got the new seal over the outdrive EASILY.

Getting it on the transon sealed up was a PAIN.

So we will see how it goes :)
 

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
Re: Replacing transom seal on a 1985 3.8 omc

if you have selectrim, trim the unit full up and down a bunch of times after installation and make sure the big clamp around the intermediate stays put
 

Newbie@boats

Chief Petty Officer
Joined
Apr 6, 2010
Messages
536
Re: Replacing transom seal on a 1985 3.8 omc

I have raised it up and down many times so far, tomorrow I plan on taking it out.

Gonna back it into the water first leave it on the trailer for a little bit and see it any water comes in...

Now I see the motor itself goes up and down...I have never see this before...is there a reason for this?
 

cr2k

Captain
Joined
Mar 19, 2009
Messages
3,730
Re: Replacing transom seal on a 1985 3.8 omc

A few things. Use Life Seal to seal it. If the rear of your stringers are bad the rear of the engine/drive will be lower then it should be and make it hard to get the new seal aligned properly.

Yes it goes over the drive and be a pain for the newbie. After awhile it only takes about 30 min to change one. DO service your tilt cavity often like everytime you haul it out of the water. failure to do so can result in oil/water in the tilt motor and a replacment is a $300 part.
 
Joined
Oct 11, 2010
Messages
18
Re: Replacing transom seal on a 1985 3.8 omc

the "motor goes up and down" that is your trim, trim is there to adjust the angle of your stern drive in relation to you boats hull with very small movements without taking it out of allingment with the driveshaft or engine, so your stern drive stays in the fully down position and the entire system motor and sterndrive tilt slightly to suit your needs eg. heavy loads, slower speeds, you would adjust this and it would help with planing, chop, fuel consumption, pulling bow up or down etc.
 
Status
Not open for further replies.
Top