i/o stern section sealer

Joined
Jul 22, 2012
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59
hey guys, itching to get the boat out and start getting it finished up. I have an issue that needs to be dealt with. Last summer, I splashed the boat to make sure the hull didn't leak, and it didn't but I had water coming in at the top part of the bottom of the inner transom plate and then I noticed that the outer transom housing, wasn't sealed to the hull. The caulking or whatever was used to seal it to the transom was no longer sealing. What is the best way to seal that up and anyone have any other ideas on where it could possibly be leaking at? Do I need to tighten up the lower bolts and pull that outer transom housing tight to the hull?

One more question about charging system. I don't know much bout the marine charging system but this last summer, I installed an actual volt meter and draws it's voltage from the ignition switch. when the motor is running and is running at 3,000 rpm, my volt meter isn't showing anything over 12 volts if that. is the external voltage regulator bad????? the motor is a mercruiser 110 I/o. If that's the case, would it be wise to just upgrade to a internal regulated alternator? What do I do with the two big red wires that went through the ammeter? I am using one as a power feed for the ignition switch but what about the other?
 
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cj8mule

Senior Chief Petty Officer
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Apr 7, 2012
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Re: i/o stern section sealer

Pictures would help, but it sounds like you might have a rotten transom.

There is a seal on that housing that you cannot see . Sometimes people put sillycone around the housing, but it is not necessary. Now assuming you have a mercruiser there are 6 bolts that you could tighten. I recommend that you check the transom for rotten wood. Without pictures I'm just seeing the lower part of that keyhole being rotten
 
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Jul 22, 2012
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Re: i/o stern section sealer

i'll have to go out to storage and try to get some pics. As far as wood, I do not believe the wood for the transom is not rotten. The wood on the inside of the transom is good from what I have seen. Holds screws good and not spongy.
 
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jbcurt00

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Re: i/o stern section sealer

CJ8's got you headed in the right direction. Unless the mounting bolts are LOOSE, I doubt snugging them up will draw the transom plate tight enough to re-seal against the transom. I don't know what the torque spec is for those bolts, but don't snap the head off of 1 trying to over tighten it, or crack the housings.

As mentioned there is a seal on the inside of the exterior housing. You have to pull the outdrive to replace it. When you do, and I think you should, you'll have better access to determine if there is any water damage to the transom. If there's a water leak, the transom has gotten wet. It may not be severely damaged, yet, but that depends on how long it leaked before you noticed.

It doesn't sound like you've done a complete rebuild:
Here is my 1966 starcraft 18' with a 110 mercruiser i/o. Had been sitting for 3 yrs. before i bought it. got the motor freed up. floor in middle of being redone and some small stuff like trim hoses, carb rebuild and upholstry need to be done yet.
^^^ From Nov 2012, and you mention having the lower unit removed, but not the complete driveline assembly.

If the transom's never been replaced, it's bare, unsealed plywood, and has given nearly 50yrs of service. It's probably time for it to retire.

Since the boat sat for 3yrs, and needed some (perhaps more then you mentioned) decking replaced, I'd be surprised if the transom plywood is in as good a shape as you think it is. Many tin owners are surprised by what they find when they pull the transom.

It's had a re-spray:
attachment.php


And from your other posts: it's a Mercruiser 110, MC-1 outdrive, correct?
 
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Jul 22, 2012
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Re: i/o stern section sealer

correct. the boat is a 1966 starcraft 18ft with a mercruiser 110 engine and mc-1 out drive. I did end up having to pull the outdrive off the outer housing but not the housing due to a shifter issue. when I go out to take some pics for a clearer understanding of what I am talking bout, i'll snap some of the transom wood also. I do believe though that it has been replaced. The reason I say that is that the wood has been painted and the hull id tag is missing.
 

Watermann

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Re: i/o stern section sealer

Glad you didn't try to over tighten those aluminum bolts! You will most likely need to purchase a transom seal kit which includes everything you need including a new gimbal bearing. Also the goop smeared around the leaking outer transom mount means that someone tried to do a half @ssed repair to keep the water out. I hate to say it but most of the time when the leak is at the transom mount it's because the transom wood has become rotten otherwise it's a solid flat surface that seals well and there is no need for goop to be around that outer mount.

There is not a cap plate inside on the transom like an OB and no HIN on a 1966 boat because it wasn't required by the CG until 1972.
 

bob johnson

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Re: i/o stern section sealer

I don't think youll need to pull the engine to replace the transom wood.....but, you might have to pull the engine to help remove the outdrive to the motor connections...

I had the two bushings that connect the motor to the inside portion of the outdrive....what a total nightmare.... it was a 1971 straight 6...that sat or 20 years....I eventually broke some parts......but I was getting rid of it anyway
you will have to disassemble all the stuff mounted on the inside wall of the transom

bob
 

Watermann

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Re: i/o stern section sealer

so, to put a new transom in, you have to pull the engine right????

Well I would if it were me, I would pull the motor, it makes the job easier with it completely out of the way. Although you could just lift the motor and move it forward enough to get in and remove the inner mount.
 
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Re: i/o stern section sealer

ok, so can someone give me a step by step on replacing this transom wood? I have found how to videos on you tube but they have all been for outboards and fiberglass boats.
 

dozerII

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Re: i/o stern section sealer

So after doing more than a couple of these I can tell you, you do have to pull the motor to change the transom gasket or the transom. The rear motor mount bolts go into the inner transom assembly. If the seal is compromised just tightening the bolt swill most likely not help you as the wood has to be wet. Changing the transom is not real hard just time consuming. Pull the motor and everything bolted or screwed to the transom. The aluminum rear deck cover and supports, all the through bolts on the back of the transom. Bend up the rear most ends of the tops of the gunwales so you have clearance to pull the transom wood up and out. Use the old transom as a pattern, make two pieces out of 3/4 ply wood then glue and screw them together with Gorrila glue, make sure you dampen the wood surfaces so the glue will set. Sand and fit the new transom, don't forget the angled clearance for the steering arm, then seal with 3 coats of spar varnish, then reinstall the new transom, torque the mounting bolts to the required torque as stated in the manual for your model.
 

barato2

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Re: i/o stern section sealer

dang he makes it sound easy......:rolleyes:

ok, so can someone give me a step by step on replacing this transom wood? I have found how to videos on you tube but they have all been for outboards and fiberglass boats.
1966, what Bluefin was saying there is that virtually every single I/O thread on here has a step by step with pix, don't waste your time on youtube.
 
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dozerII

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Re: i/o stern section sealer

dang he makes it sound easy......:rolleyes:

ok, so can someone give me a step by step on replacing this transom wood? I have found how to videos on you tube but they have all been for outboards and fiberglass boats.
1966, what Bluefin was saying there is that virtually every single I/O thread on here has a step by step with pix, don't waste your time on youtube.

Well actually they are after you do a few.
 

Watermann

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Re: i/o stern section sealer

Well actually they are after you do a few.

When you do it too many times we just forget to explain a couple things. :D You also need to fab up and attach a horse collar on the inside of the transom wood just like the one you have, most likely 3/8" ply. When you cut the new transom wood to size with the saw, the top cut has to be an a 15 degree angle inboard to allow for the angle of the transom so the cover will fit back over the top of it all.

Sounds like some serious fun to me, not that tough at all!!!
 
Joined
Jul 22, 2012
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Re: i/o stern section sealer

ok. cool. thanks for the breakdown. it does sound easy. Is it smarter to pull the outdrive first before the motor? or other way around.
 

Watermann

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Re: i/o stern section sealer

Outdrive has to come off first, then go inside the boat and start disconnecting the motor. Pull motor and then back to work removing the inner transom mount.
 

jbcurt00

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Re: i/o stern section sealer

Ask for suggestions if you don't have access to an engine lift or overhead attachment for a hoist to get the motor up & out of the boat.

Depending on the height of the back of the boat & how high the boat sits above the trailer, some lifts can't clear the transom
 

barato2

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Re: i/o stern section sealer

Ask for suggestions if you don't have access to an engine lift

and how....lots of creative solutions here....trees, A-frames, backhoe buckets, tall stepladders with a beam laid across tops, etc etc etc
 

bob johnson

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Re: i/o stern section sealer

2zste85.jpg



I vote for the tree! preferably in, or near the driveway!

this is what you will be working on...
2vlku81.jpg



bob
 
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