OMC to Merc with Seacast pt. 1

[wire2]

I wanted to modernize my drive, pulled the stringer out and acquired alpha gen 2 parts to replace it.



I discovered the plywood below the waterline was mush. Got it all out in ~3 hours.



I made a 3-D template to mimic the Merc opening. Saves Seacast, saves a lot of cutting after. I mounted it on a piece of laminate on the X dimension.



Template board fastened to boat.



From inside.



2 layers of glass cloth & resin on the open area.



I have to stop at 6 pics, will follow up with "OMC to Merc with Seacast pt. 2" at http://forums.iboats.com/boat-restoration-building-hull-repair/omc-merc-seacast-pt-2-a-225271.html and pt 3 at http://forums.iboats.com/boat-restoration-building-hull-repair/omc-merc-seacast-pt-3-a-225745.html

[Gary H NC]

Nice work! Seacast is some good stuff.Should last forever when its finished..

[Boomyal]

How thick was the outer glass of the transom? What did you use to make your merc cutout template? How did you determine the height of placement in relation to your motor mount stringers and all the merc engine mounts?

Also, will the width of the seacast be sufficient for a transom mounted O/D? With your transom config, I don't see how they would have built a thick transom all the way across. Were you ever able to see a model of your boat that originally came with a merc?

[wire2]

How thick was the outer glass of the transom?

Half inch

What did you use to make your merc cutout template?

I found a picture of template on the web, blew it up so that the bolt centers equalled my transom assembly. Was 1325%. I glued a piece of 5/8 plywood to a 2x8, cut it to the template. Then made a 1-3/4" dowel on a lathe, cut 2 pieces to 45° and fit them at the top for the steering arm clearance.

How did you determine the height of placement in relation to your motor mount stringers and all the merc engine mounts?

So far it's strictly based on the X dimension. I will adjust the motor mounts as required.

Also, will the width of the seacast be sufficient for a transom mounted O/D? With your transom config, I don't see how they would have built a thick transom all the way across. Were you ever able to see a model of your boat that originally came with a merc?

The plywood that was there was essentially the same as what I've formed, it never went all the way across. No need to. Glastron made the boat with no opening, the dealer cuts the opening for the customer's choice. At the time, the salesman pointed out that the OMC had a much smaller turning radius, was supposedly quieter, so I said ok.

Did I cover it all?

[79Glastron]

Wire,

Wow, this is just the thread I'm looking for! I have a `79 Glastron that I would like to convert to a merc too. Keep up the good work, can't wait to see how it turns out. What engine are you using? I'd like to use the alpha w/ 4.3 V6.
Thanks

Randy

[Boomyal]

Did I cover it all?

Sure did wire, thanks! Interesting re the transom. My 20 ftr came with a stringer. The transom would not have accomodated a transom mounted O/D. I would have to build it out from side to side to do what you did. I think my glass was only 1/4" thick and of course it only had the wood around the immediate boot opening.

[wire2]

Wire,

Wow, this is just the thread I'm looking for! I have a `79 Glastron that I would like to convert to a merc too. Keep up the good work, can't wait to see how it turns out. What engine are you using? I'd like to use the alpha w/ 4.3 V6.
Thanks

Randy

Thanks, Randy. Engine is 5.7
Have a look at http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/stainless-manifolds-risers-225140.html for a picture of it. I think you'll like it.

[79Glastron]

wow wow wow, very nice work! Another reason why I wish I had a tig and more time. Great work!

[Manipulator]

Wire2, I have never seen thru-hull exhaust on a Stringer. Was that hooked up to the Stringer setup or did you recently install it for the merc setup.

[wire2]

Wire2, I have never seen thru-hull exhaust on a Stringer. Was that hooked up to the Stringer setup or did you recently install it for the merc setup.

Ah, you picked up on that! Yes, I had it on the stringer.

It took a bit of creative thinking, to allow the headers to tilt with the engine trim while the transom pipes remained stationary. I first considered an accordian style, kind of restrictive.

I settled on a piece of smooth (inside & out) rad hose 3" ID clamped to the transom pipe 10" long. There's a piece of 3" OD stainless tube clamped on the header outlet, also 10", inside the hose. The tube slides in/out with trim.

I lube it once a season with clear synthetic grease. It fits perfectly, not a drop leaks. Header cooling water is mixed with exhaust so temp stays under 130°, hose is rated for 300° F.

[Manipulator]

Wow! That's a pretty cool setup. I often thought about converting to thru-hull exhaust but the fact that the motor goes up and down posed a problem. I cannot see doing it with the log setup and the stock elbows. I have the GM 5.7L and I was going to get new merc manifolds with center risers. Then use exhaust hose. I did find an exhaust tip that had a SS flange and a rubber diaphragm that the tip slides through. This would allow the tip to pivot up or down as the motor raised and lowered. Not sure if it would allow the tip to slid though. Still considering converting it some day. What did you use to close the connections at the intermediate? Some sort of cap I imagine??

[wire2]

.... What did you use to close the connections at the intermediate? Some sort of cap I imagine??

No, the intermediate is still connected as well so I can run quiet. But I did get rid of the OMC cast iron pipes down to the mid drive though. They were 12 lbs each! I replaced then with 4" aluminum tube, 1/8" wall. About 1 lb for both of them.
There's a pic of my diverter at http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/simple-thru-hull-exhaust-225442.html