transom/engine question

SonOfABeach · #1 08-25-2008, 04:31 PM

This is probably a simple question but I'm new to the world of boat owning/repairs. I have a 74' 20' CC with a questionable transom. Questionable because with the Johnson 200 that is currently on it there is no flex when putting pressure on the engine, can stand on it and no problems, but drilling a thru-hull for the bilge pump (the previous owner never plumbed the pump) in the mid-upper starboard side of the transom what came out was disturbingly wet falling apart wood.

I was planning on repowering the boat soon, but I am not made of money, so am only able to tackle one project at a time. I've been glued to the posts on here like stricks legend of a post, fishjacks, and oldbluesplayer trying to absorb as much info as I can. I see that most (if not all) of the transom rebuilds on here was a change to enclose the entire transom or at least raise it up 5". I like the idea of both of these, specifically the enclosing the transom, just the idea of having to purchase a bracket (I'm afraid my fiberglass skills aren't nearly on par with anyone else on this site to be able to construct one) on top of the cost of the transom repairs is not appealing (but not impossible).

My real question is my current engine is a 20" model, if I raise the transom or enclose it, would I be able to use my current engine on the modified transom (either 5" higher or on a bracket if closed) or would I have to repower before I could use the boat again? I'm leaning towards closing the transom for cosmetic and safety appeal but am unsure about brackets and engine length application. Any info would be greatly appreciated. Thanks all.

--Beach

Ryank · #2 08-26-2008, 06:42 PM

I had a 20 and ran several different engines on it. I was slightly worried about a 30 yr old transom myself even though it had little flex. I had an aluminum plate cut out to the shape of the transom and a smaller plate on the inside and it had raised the height by about 5-6 inches kind of as a splash shield. I had to use a jack plate to do this and use a 20 inch shaft engine. When I purchased a new engine I purchased a 25" shaft and then had to adjust / raise the jack plate which helped to get the cav plate about 1 1/2 inches above the bottom and proper trim, and it also raised the power head up and out of the water quite a bit helping to protect it from salt water etc. Boat handled great for several years and I never ever worried about the transom again. If yuo are worried about the transom a great deal I would not put a large bracket on it without having it inspected by a pro first. A jack plate is not quite as much stress.
Just my .02 cents. Hope this helps

SonOfABeach · #3 08-27-2008, 11:13 AM

Thanks for the reply. So if I had the transom replaced/closed in, and put a bracket on it, I could use a 20" or 25" engine on the bracket, just depending on the engine height I would mount the bracket higher or lower on the transom?

Bushwacker · #4 08-27-2008, 12:05 PM

Most brackets are made for 25" shafts. Normal formula for mounting on brackets is, starting with cav plate flush with bottom of hull for non-bracket mount, raise motor 1" for each 12" of setback. That's still just a starting point, as I was able to raise mine 2 holes from there.

A bracket also spreads engine load across entire transom, instead of concentrating all the load in the center like a conventional mount does.

SonOfABeach · #5 08-27-2008, 03:25 PM

I see. I'm asking all of this because I'm getting my transom inspected this week and if it is in need of repair I'm going to bite the bullet and rebuild it. Which then the decision has to be made whether to leave it open like it was from the factory in 1974, raise it 5" like some people have done on here, or close it up completely. I've been all over the rebuild threads on here and haven't found anyone that I can remember that has kept it at the same height.

As I understand it right now if I leave it the same height I'll have no issues using the current 20" engine, but will have to do some modifications (add a bracket or jack plate) if I closed it or raised it, correct? And being that most brackets are made for the 25" shaft engines, would my best choice be a jack plate in those situations? Would I even be able to install say a 6-8" setback jack plate if I closed my transom in and be able to tilt the engine up w/o the powerhead hitting the back of the transom?

Sorry for all the beginner questions, long time boater, first time boat owner, not used to being the one making all these decisions. This site has been an amazing resource so far and will continue to be.

dlb511 · #6 08-27-2008, 04:25 PM

You could probably have the shaft extended on your current engine to 25". Most engines have an extension kit available. That way you could rebuild the transom to 25", as it should be, and still keep your current engine. At least until the funds are available for an upgrade. No sense rebuilding a transom or buying a bracket for 20" shaft. If you ever sell, the new owner will certainly balk at a 20" transom, rebuilt or not.

SonOfABeach · #7 08-27-2008, 04:39 PM

What would be the negative of rebuilding the transom, and getting a bracket or jack plate for a 20"? What would be the benefit of having a 25" on a bracket or jack plate with a closed transom vs a 20" on a bracket or jack plate with a closed transom?

If there wouldn't be a difference then when I repowered I'd just put a new 20" on it, vs modifying my current engine and then buying a new 25" engine.

Ryank · #8 08-27-2008, 05:04 PM

I was only able to use a 20" motor because all I did was raise the top of the transom 5-6" and still had to use a jack plate to get the adjustment right. If had my choice I would close in the transom and use a scissor lift hydraulic jack plate that would be the ticket.

SonOfABeach · #9 08-27-2008, 05:17 PM

So closing in the transom and putting say a portabracket or something similar from bob's on it like this one I found in the for sale ads:

Would accommodate my current 20" and in the future I could repower with another 20"?

Bushwacker · #10 08-27-2008, 06:02 PM

Quote:

. . And being that most brackets are made for the 25" shaft engines, would my best choice be a jack plate in those situations? Would I even be able to install say a 6-8" setback jack plate if I closed my transom in and be able to tilt the engine up w/o the powerhead hitting the back of the transom?

I gather you want to use existing 20" shaft engine on a 25" transom or bracket, which makes sense if it's still in good shape. The main idea of a 25" shaft is to get powerhead higher above waterline so it's less likely to get dunked by a following sea, or when backing down on a fish, etc. A jack plate would probably work. Check Island Trader's posts for one on a Porta Bracket, which would probably allow you to tilt engine with a solid transom. Another, and possibly cheaper, option is to simply add a 5" extension kit to existing motor. I believe a forum member in Hawaii converted a 20" 115 E-Tec into a 25" motor a few months ago. Don't know who makes them but probably worth investigating. Maybe your local dealer could point you in right direction.