Re: 2005 ELH 25hp Murcury extra long shaft
Thanks for posting those pics. It helps. One thing I see might be a problem is that even if you put a jack plate on it to raise the outboard up which is needed or the cavitation plate (the large plate on the bottom of the lower leg). If its underwater it will drag and kick up a lot of spray. Mine rides on top of the water or a little below when boat is up on plane.
What I woul;d be concerned with is the style of that transom. Most rigs have a higher transom with a cutout that you hang the outboard on. That cutout when measured from top to the bottom of the transom is usually 20 inches.
If you were using say a 9.9 and slowed down real quick its not going to kick up much of a wake that bounces off the back of the transom. But a 25 hp and being a 2 stroke is nice and light and it will make that rig move pretty quick. So when you slow down real fast the wave washing back against the transom might come over the back. Same thing can happen if you're fishing and some jerk flys by you behind your rig on a big boat and throws off a big wake. . . If its a heavy 4 stroke you could be in trouble as the water line is high up on the transom. Your 2 stroke might not be as much of an issue but you have to get it in the water and see where the water line is?
I'm no expert on this stuff I'm just speaking from experience with small aluminum boats and outboards that are too heavy for them.
This is why when they build a boat, they attach a capacity plate on them. Problem is when you buy an older boat those plates were for 2 strokes that are much lighter than the newer 4 strokes. Most decent boats have whats called a splash well. If a wave washes over the transom most of it catches in the splash well and drains out the holes on each side back into the lake. From you pics and being homemade I don't see a splash well which makes it even more dangerous. This is why I sold a 13 foot aluminum because it had no splash well and waves would wash in from boats flying by when we would be sitting there fishing and it only had a 9.9 Merc 4 stroke on it.
Your boat being wood or fiiberglass would probably be OK for a 25 2 stroke. I'd still drive into a boat dealer and ask them their opinion as to that motor on your style homemade boat. All hulls are different.
If you are dead set on using that long shaft they make splash shields in plexiglass that attach to the left and right side of the transom which prevent waves splashing in. I think Lundboats.com search their baot catalog as I saw some of their models coming with splash shields last season. You are going to have to use a jack plate or build up the transom higher. I raised my outboard 1.5 inches by have an alumium bar made up a t a local metal shop. I'd also be concerned if you raised it higher you are throwing the center of gravity off. Can't tell until you try it as all hulls are different.
I'd put the outboard on the boat and see how it handles at low speed. Don't try and plane with it. Start another thread saying you need to know how much to ask for on Craigs List for a 2005 extra long shaft 2 stroke Merc? There are a lot of 2 stroke lovers out there so it will sell.
A shaft can be shortened but the cost is too much. You can also go to a boat rental place and rent a 25 hp for a few hours for a 20 inch transom, put it on your boat and see how it handles. Used ones pop up you just have to be patient and willing to drive out of town to pick one up.
Here is a link to what a transom splash shield looks like:
http://www.wavewackers.com/
I was going to add the plexiglass splash shield to my 13 foot aluminum (or make one myself) which had real low sides (called freeboard) but with all the expense, time and effort . . . I sold that boat and bought a brand new Sylvan 13 foot aluminum Alaskan deluxe complete with a full vinyl covered deck for like $1200! This model had real high sides. I already had the Merc 9.9 4 stroke for it.
