Vertical Extension plates: 20" engine on whaler transom

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Author Topic:   Vertical Extension plates: 20" engine on whaler transom

ToneDef posted 07-10-2012 09:13 PM ET (US)
I know this has probably been discussed ad nauseam, but I could not find this particular answer...
I've got an older 13 footer that I've been readying for the water and I've got a longshaft Merc 40 that I'm planning on hanging off the back. My original plan was to fab something like the Kentfab plate and fill/raise the notch in the transom, but I think something along the lines of the CMC 5" Vertical Extension would be a little cleaner, easier to fab, and easier to install/remove.
Here:
http://cook-mfg.net/cart/index.php?main_page=product_info&cPath=10_13&products_id=13
The engine weighs apprx. #180. My only concern is in the through-bolting of the Vertical Extension tabs. If I choose to make the extensions long enough to reach almost down to the waterline (so to distribute the force of the engine over the largest possible transom area), is it safe to through-bolt the lower ends of the Extensions?
They would no doubt extend down beyond the area that "bumps forward" about 1" in the motorwell (on the interior side of the transom), and therefore I would be drilling and bolting directly through this apprx. 1" thicker area. Is this area solid wood beneath the glass, or is it foam-cored over the uniform thickness of the transom wood?
If so, should I scratch the idea of through-bolting through this lower portion, as it would probably just compress and crack the glass/foam?

Thanks!
ToneDef posted 07-17-2012 08:09 AM ET (US)
anybody? bump.
contender posted 07-17-2012 05:10 PM ET (US)
More surface area is better to handle the load, What year whaler are you talking about? I did the same thing on my old (1975) 16 whaler, but I also just redid it and I reinforced the corners inside and out of my transom. I made a inside plate (1/8" aluminum) shaped like a trapezoid to cover the four bolt hole areas, Each of the holes were pre drilled 9/16 inch and then filled with a fiberglass paste mix. This was done to make sure there was a good seal all around the bolt so that no water could enter the transom. The holes were then re-drilled for the 1/2 inch bolts, and I use 3m 5200 to seal the holes as well, A bead of 5200 was place around each hole and a boarder around the plate as well. Hopefully this sealed my holes in the transom....I also have a smaller 11 whaler that I redid the transom and fiberglass (did the corners as well) the notch one inch to raise the engine one inch. But this was a 15 inch transom with a 15 inch shaft engine...I through bolted this engine as well but only use two bolts and a wide transom plate out of the same material. The engine also has two screw clamps as well...Take care

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Author	Topic: Vertical Extension plates: 20" engine on whaler transom
ToneDef	posted 07-10-2012 09:13 PM ET (US) I know this has probably been discussed ad nauseam, but I could not find this particular answer... I've got an older 13 footer that I've been readying for the water and I've got a longshaft Merc 40 that I'm planning on hanging off the back. My original plan was to fab something like the Kentfab plate and fill/raise the notch in the transom, but I think something along the lines of the CMC 5" Vertical Extension would be a little cleaner, easier to fab, and easier to install/remove. Here: http://cook-mfg.net/cart/index.php?main_page=product_info&cPath=10_13&products_id=13 The engine weighs apprx. #180. My only concern is in the through-bolting of the Vertical Extension tabs. If I choose to make the extensions long enough to reach almost down to the waterline (so to distribute the force of the engine over the largest possible transom area), is it safe to through-bolt the lower ends of the Extensions? They would no doubt extend down beyond the area that "bumps forward" about 1" in the motorwell (on the interior side of the transom), and therefore I would be drilling and bolting directly through this apprx. 1" thicker area. Is this area solid wood beneath the glass, or is it foam-cored over the uniform thickness of the transom wood? If so, should I scratch the idea of through-bolting through this lower portion, as it would probably just compress and crack the glass/foam? Thanks!
ToneDef	posted 07-17-2012 08:09 AM ET (US) anybody? bump.
contender	posted 07-17-2012 05:10 PM ET (US) More surface area is better to handle the load, What year whaler are you talking about? I did the same thing on my old (1975) 16 whaler, but I also just redid it and I reinforced the corners inside and out of my transom. I made a inside plate (1/8" aluminum) shaped like a trapezoid to cover the four bolt hole areas, Each of the holes were pre drilled 9/16 inch and then filled with a fiberglass paste mix. This was done to make sure there was a good seal all around the bolt so that no water could enter the transom. The holes were then re-drilled for the 1/2 inch bolts, and I use 3m 5200 to seal the holes as well, A bead of 5200 was place around each hole and a boarder around the plate as well. Hopefully this sealed my holes in the transom....I also have a smaller 11 whaler that I redid the transom and fiberglass (did the corners as well) the notch one inch to raise the engine one inch. But this was a 15 inch transom with a 15 inch shaft engine...I through bolted this engine as well but only use two bolts and a wide transom plate out of the same material. The engine also has two screw clamps as well...Take care