Renewing a rotting transom- What is the best entry point?

Sinkingslow

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[/ATTACH]049.jpgRe: Removing tilt trim and 115 Mercury outboard for a newbee.



I now have a question on where to start on the repair of the transom. I am including pictures of the condition of the transom. I have seen u tube videos talking about grinding off the outer transom and finding the rotten wood thru the backside and I had a person suggest that I cut the cap just above the rear wheel step to remove the cap to get to the rotten wood. Not sure where to begin. Very open to suggestions!
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bigdirty

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Re: Renewing a rotting transom- What is the best entry point?

I will say, my experience has always been with I/O and I'm not sure if there are any major differences with an outboard setup, but my thought would be to remove the cap, or you could just cut remove the section over the transom, and then re+re the wood from the inside and re glass.. that leaves the original outer glass work intact, and you can easily make up new transom wood to fit nicely. Also, even if the new glass job doesn't look pretty, its hidden in the end.. although there will be a cut cap to repair and make look nice, if you did it that way.
 

Woodonglass

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Re: Renewing a rotting transom- What is the best entry point?

There are many methods for repairing your transom. You've mentioned a few. If you spend some time searching the Threads on Transom Repair here on the forum you'll discover that the preferred method discussed here, is to remove the top cap of the boat to gain access to the transom and the second most preferred method is to cut the gunwales slightly forward of the splashwell. I would also mention that if your transom is in this condition there's a HIGH probability that the stringer system below deck is also in a bad state of affairs and you should be prepared to do a full restoration of the boat. In order to remove the old transom and replace it you will need at the very least to remove the rear portion of the deck to gain access to the transom and at this time you'll be able to ascertain the condition of the stringers near the stern of the boat. What kind of boat is this? What year, size etc...
 

Sinkingslow

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Re: Renewing a rotting transom- What is the best entry point?

The boat is a 1974 19 ft Star fiberglass with a 115 horse Mercury outboard.
 

Woodonglass

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Re: Renewing a rotting transom- What is the best entry point?

Since she's 40 yrs old, I'm betting the stringer system is rotten as well. If it were me, I'd be planning on a total restoration. Deck, Stringers and Transom. This link will help explain some things...Fabricating Decks, Stringers, and Transoms"
 

Sinkingslow

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Re: Renewing a rotting transom- What is the best entry point?

Thanks. I will go that direction. Should be able to knock it out in a day, right?:) Just kidding. I really am going to put more time, effort and money into it. The hulll is no good to anyone the way it is. I appreciate the link. It already answered some questions. Thanks
 

Sinkingslow

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Re: Renewing a rotting transom- What is the best entry point?

Got the rub rail off. I am wondering about the wiring. When I lift the cap off after taking off the windows. I wonder how to best keep the cables and wires in tact. New territory for me, but I am willing to try. Any suggestions?
 

Woodonglass

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Re: Renewing a rotting transom- What is the best entry point?

Label em with Tape and cut em. You can put em back on the go back!!!!;)
 

Sinkingslow

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Re: Renewing a rotting transom- What is the best entry point?

Now ready to start cutting out the rotten wood of the transom. I am likely going to have to replace the stringers and deck. Are they any suggestions about the type of wood or products. Never done this before. What is the best way to make a template, cardboard, styrofoam board?
 

Sinkingslow

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Re: Renewing a rotting transom- What is the best entry point?

Thanks that is a good thread. After reading it seems the GT1000000 thread suggests to go with exterior 3/4 inch plywood for the transom. Why would a penny saving person use marine grade plywood? Does it save time in preparation. I assume it would last longer, right?
 

Sinkingslow

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Re: Renewing a rotting transom- What is the best entry point?

Next question. I have the cap off the boat. The gas tank is full. I noticed that the manufacturing date was 1972 on the tank. I do not sense that the tank is bad but I am wondering about having it inspected. I am in Idaho. Any thoughts?
 
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greenbush future

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Re: Renewing a rotting transom- What is the best entry point?

Next question. I have the cap off the boat. The gas tank is full. I noticed that the manufacturing date was 1972 on the tank. I do not sense that the tank is bad but I am wondering about having it inspected. I am in Idaho. Any thoughts?

Empty the tank and inspect what comes out, may be good gas, may be a mess. Pressure test the tank to ensure it's good, or replace with new. You have it tore down, now is the time to make sure it's in safe running condition. I would replace all hoses with Ethanol friendly types so you don't have rubber gunk entering your engine.
 

Sinkingslow

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Re: Renewing a rotting transom- What is the best entry point?

Thanks. I have never "pressure tested" a gas tank. How do you do that? Great idea about replacing the hoses with Ethanol friendly types. I did not know they existed.

Also, I am going to replace the carpet. Do you recommend any type?
 

jbcurt00

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Re: Renewing a rotting transom- What is the best entry point?

Many radiator shops will pressure test a gas tank, but it needs to be empty & probably fume free. A good cleaning after you get the gas out is a good idea anyway.

This ^^^ supposes that it's an aluminum/metal tank not poly/plastic. A radiator shop may not test a plastic tank.
 

GT1000000

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Re: Renewing a rotting transom- What is the best entry point?

Pressure testing a fuel tank is fairly easy...
You only need to raise the pressure in the tank to 3 psi or if there is a label on the tank that specifies what the test pressure should be, follow that recommendation.
By sealing off the openings, you can hook up a bicycle pump [some redneck engineering may be required] and pumping it up to about 3-5 psi...don't go over that because you can damage the tank...then use some soapy water around any suspected areas of leakage, around the welded seams, the sending unit, etc...
Here are some of the USCG technical specs for pressure testing a fuel tank...Fuel Systems - Tests

 

73Chrysler105

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Re: Renewing a rotting transom- What is the best entry point?

I thought the tank pressure test was to be done at 4psi??
 

GT1000000

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Re: Renewing a rotting transom- What is the best entry point?

I thought the tank pressure test was to be done at 4psi??

Been looking thru the interweb for where I read the way to do it, but most tanks will show leaks at 3psi, but like I said, or I should say, like the Coast Guard specs say, if there is a manufacturers label on the tank that specifies test pressure, then that should be your guide...

OK, I found this...
http://ia600402.us.archive.org/7/it...93/abyc.H-24.1993.pdf#page=10&zoom=auto,0,797
http://ia600402.us.archive.org/7/items/gov.law.abyc.H-24.1993/abyc.H-24.1993.pdf
Go to page 10...look under 24.17.4
 
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Sinkingslow

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Re: Renewing a rotting transom- What is the best entry point?

My tank shows that 4 psi should be the pressure. I called a couple of radiator shops and they do not test them anymore. One boat place suggested putting water in the tank and looking for leaks. I likely try the bycycle pump and some soapy water.

Also, I have now a good look at the transom which has some firmness but shows rot. I can not see the stringers and there are no soft spots on the deck. My curiousity tells me to cut out some of the deck to see if there is stringer damage. It is 42 years old. Advice?
 
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