Twin I/O to Twin Outboard Conversion Project

Thanks for the recommendation @fallguy Looks pricey, but I'll check it out.

As for the 2" step . . . I am not surprised about no comments, because some of these design aspects would require testing. It looked like going with no step was going to be a more predictable result. Again, hard to say exactly. Since the extension pod is going to be even with the existing hull there won't be an angle of incline to consider. In my earlier design revisions with the step it as about a 2˚ 'angle of attack'.

 

It has been about 20 years since I pulled an engine out of my boat (454 V8 Mercruiser). . . only took a few hours.

As for this boat/engines, it is way more challenging, since there is more 'stuff' about the engine. The cooling system is way more complicated as is the electrical system. There are about 14 items that need to be disconnected: hoses, electrical wiring, bolts, etc. Referencing the service manual, I made a list. Some things are easier than the 'days of old' and some things are harder. I spent much of the day unbuttoning and labeling things . . . got about 2/3 of the way done.


.
At the back of the engine buried beneath the hoses and wiring there are the rear mount bolts. I'll need to take the poppet valve and hoses off to gain access. I've already removed some things, but there is more to go. I decided to cut the large ground wires, rather than wrestle with them. There should be enough slack in them upon re-working the transom.

Since things are taking longer than I had planned, I'll have to re-visit my schedule. I'd really like to be sending the boat off to the re-power shop in January/February.
.

 

It took a few hours disassembling things, but I finally got the rear mount bolts out.
.

.
The older Mercruisers did not have much stuff at the rear of the engine and the bolts were much more accessible. New engines . . . not so much.

 

Starboard engine is out. . .

.

.
I found a couple of wires that were still connected as I lifted, but that was quickly resolved. On to Engine #2.

 

Two full turn strap up top, nice.

Good job, you're lucky there where only two wires still attached !

 

And engine #2 is out and down. . .


.

.
The port engine needed to be guided out since it was partially obstructed by the rear settee frame.

All set. I'm glad the heavy lifting is done for a while.

 

Transom assemblies are out. . .

I took the engine mounts and transom assemblies out today.
.

.
The transom core is a medium gray foam material. I'm thinking it might be Divinycell?
.

.
Thinking that it might flex a bit . . .I am considering glassing a flange around where I will have the cut-out openings as an extra stiffener along the fastener edges. Not sure if that would be overkill.

 

This transom is not designed for outboards forces load.
Again I'm against bracket idea .

 

Pretty hard to go overkill on a transom.
Arguably the weakest, most vulnerable, part of a boat.

 

Wonder what density it is, are you going to do internal stiffeners on the inside? Seems like most the thrust will eventually be on the new transom and transfer to the hull bottom and sides.

Cool to see the progress.

 

Here is what I plan on the transom stiffening. (previously posted) . . . just looking at it now, it may be enough.

 

I'm guessing either H80 or H100 Divinycell. Those are the densities for transoms.

 

Understood . . . Keep in mind that this boat also comes in an outboard version done via a bracket.

.
I'm not a fan of how the manufacturer has done their outboard version. It also seems that the factory version acknowledges that there is not enough planing surface as indicated by the 10" static plates attached to the hull.

Your comment has prompted me to take another look at what the manufacturer of the boat does structurally to accommodate the bracketed outboards.

.
I have not given it too much thought previously, but it is apparent that they add additional stringers (and knee braces) directly in line with the engine spacing and run those within the swim deck cavity (red arrows). My design is to tie into the outside engine stringers with knee braces. (purple lines).

I may want to add those additional stringers, given the foam core transom 'discovery', as that modification will also help with installing/supporting a flat surface within the former engine compartment.

 

I would think two, full height stringers running all the way forward from engine centre lines ( or close to them ) would be the way to go.

Where are you at with the 2" step?
Given the planing issues you've had, I would eliminate it.

Looks like you're making good progress.

 

Yes, the step was eliminated (post #52)