1989 OMC Cobra 4.3L taking on water through transom area.

[DunbarLtd]

I am working on a 1989 Four Winns with a OMC 4.3L(v6) . I believe the outdrive is a cobra and when launching the boat last week I noticed a pretty good leak coming in through the transom area. It slows down when I gave it throttle for some odd reason but maybe thats relevant info.

This is my first inboard outboard so Im kinda new to these outdrives. Im not sure what part may be failing?

Any ideas how I can diagnose this problem without taking the whole darn thing apart?

 

[Scott Danforth]

first, you need to get your head in there and look to see where the leak is coming from

first thought is the fact its a 32 year old boat, specifically a 32 year old OMC branded boat. most likely the transom is soft

however you could have leaking bellows or other items.

at a minimum:
you need to look to see where the leak is coming in
you need to pull the drive and replace the bellows if you have not done so yet
you need to test drill your transom and look at the shavings.

 

[DunbarLtd]

How does the transom wood get wet? When they build these boats dont they seal all the raw edges of the wood with fiberglass or at least gelcoat before mounting the drive? Why is this such a problem with older boats glass boats? Seems like an oversight from the manufacturers. Im sure rotting transoms have been a problem since day one way before the 90s and they couldnt figure out the problem? Are the newer boats the same way or have they went away from wooden transoms? Just seems like an easily fixable problem by making sure to encase all the raw edges of wood with fiberglass. Maybe the manufacturers were just too cheap to spend the time to do it right?

 

[Scott Danforth]

How does the transom wood get wet? When they build these boats dont they seal all the raw edges of the wood with fiberglass or at least gelcoat before mounting the drive?

No, they cut the drive hole with the precision of a drunken lumberjack wielding a chainsaw and slap the drive on the back. they do not seal the edges of the keyhole. In the 80's there was less precision used.

Why is this such a problem with older boats glass boats? Seems like an oversight from the manufacturers.

Its a problem with all boats. design life is part of all manufactured components. They are designed to last x number of years then be replaced.

Cars have a design life of 15 years or 180,000 miles (about 300,000kms). Small boats have a design life of about 15 years as well. its not an oversight, its simply making a product as cheaply as possible that needs to be replaced in about 15 years so they can keep making boats (just like they continue making cars, lawn mowers, toasters and light bulbs).

remember, design life is the life expected with minimal service and maintenance. service life is what you actually get with the service and maintenance applied.

Are the newer boats the same way or have they went away from wooden transoms? Just seems like an easily fixable problem by making sure to encase all the raw edges of wood with fiberglass. Maybe the manufacturers were just too cheap to spend the time to do it right?

many modern boats in the past 5-10 years are wood free using various composites. however they still only have about a 15 year design life. the plexus or other glue that holds the stringer tubs together can only flex so many times prior to the joint failing.

remember, boats are slapped together as cheaply as possible to make the boat company money. they do not make money by using the best materials and having a design life longer than 15 years. most new boats will be sold before the warranty period is out. there is no incentive for boat companies past the first buyer.

However you still need to look to see where the water is coming from. you may be lucky and have a completely dry and rot free transom and be leaking thru the drive bellows. until you look, you wont know.

 

[DunbarLtd]

Well alright then. That about says it all. Ill see what I can find. Thank you sir.