Twin I/O to Twin Outboard Conversion Project

Would think that's plenty. Or at least stronger than the rest of the hull....

Kinda surprised its a lower weight core for the outdrive. At any rate with all yhe internal bracing in the bracket as well as the support in the existing hull, it looks very much like suspenders and a belt.

I see plenty strong and a tremendous amount of fairing work...


As an aside note, got drafted to help run and unload some freight for a friend of the wifes on a Particularly miserable weather day. Rig was setup with Optimus joysticks and 300b suzukis. Thought of your project as it was a boat previously outdrive powered (alloy boat converted 10 years ago on its third ob repower). Owner loved the duo props, but admitted they were new enough to not have seen long term wear issues. He had existing accusteer hpu pump and hydraulic Helms as well as a nmea 2000 gyro compass so his jog lever installs wasnt crazy expensive. Seemed like a system that worked seamless, despite being an amalgamation of pieces and parts. Still can't get over how well those duo props work in the slower range of speed.

 

It's good to know about the Optimus Joystick. I'm leaning toward the Mercury V8 . . . I know there were some issues early on with the Suzuki dual prop motors but they've made some improvements. Kind of a toss-up between more cylinders (V8 vs. V6) or more props

 

A quick follow-up on the paint remover question . . . it needed to be 'non-caustic' so as not to harm the anodized surface of the drive.

I got some of this stuff and tested it . . . seemed to be OK in softening up the anti-fouling paint (Trilux 33) not harming the metal surface.

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I will say that the SeaCore version of outdrives and engines is the real-deal if you are going in ocean waters. This boat/engine has been in ocean waters seasonally for 10 years and all the bits and pieces came apart easily with very little signs of corrosion. The Y-pipes look as if they were new.

 

Note to self . . . and any folks doing this type of conversion:

When the engines and associated drive components were taken out of the boat, the tongue weight of the trailer increased dramatically. My estimation, based on 2,250 lbs being removed from the stern, increased the tongue weight by about 1,000 lbs.

I know many folks do the conversion with the boat on blocks & stands . . . I just happen to have the boat on a trailer and have been using such to move the boat in and out of the way while the gantry remained in place.

Anyway, "-1" tongue jack. A new (more heavy duty) one is on order and I ordered a tongue weight scale thingy.

 

A bunch of material is on order. I have six 4'x8' sheets of Coosa board arriving tomorrow and some VE resin and fiberglass cloth arriving later in the week. Soon it will be time to start building the extension pod, rather than merely talking about it.

 

A quick update on the paint remover . . .
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It works well . You can see the black anodized surface under the lifted paint. I let the "SmartStrip" sit for a couple of days and then I'm using the pressure washer to clean it all off. Some areas need a second treatment, but overall it works well.

 

Nothing like having too much to do . . .

I've been working on getting the (former) engine bay cleaned out, The sterndrive engines cleaned up, and the extension pod material ordered.

I have the engines pretty well cleaned up . . . still working on the outdrives, then will be the transom assemblies

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I plan on pulling all of the wiring in the engine bay back . . . some of it originates at the helm

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For some reason, I did not realize there was a ventilation duct on the port side. . . pretty well hidden by the engine. I'm thinking that I'll be re-routing some of the ducting. Not sure how necessary the ventilation is with outboards, but the below deck fuel tank is a consideration. I'll still have ventilation when I put things back together.

The Coosa board arrived today

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Fun to see the project going along. Boy that's fast shipping for full sheets. I always forget how fast stuff moves in the normal world.

 

There is a specialty plywood retailer (https://www.premiumply.com/) about 20 miles away. They stock Coosa board. Pricing was pretty reasonable and they delivered at no extra charge. I called them Monday for a next day delivery. ($2,300) for 6 4'x8' sheets.

There is also another retailer (LBI Fiberglass) not too far away (Groton, CT) - they had another product called Endura, but I was not too sure about it for this application.

 

Speaking of Coosa board . . .

I have read about a couple of instances where fiberglass had poor adhesion to the Coosa board and eventually delaminated. Not sure about the details, but I am wondering if those with experience using Coosa (or similar) have any guidance in making sure there is a strong bond of Coosa and the fiberglass laminate. Supposedly surface sanding is not needed, but I am wondering if that helps (or hurts).

I'll be using Vinyl Ester resin and 1708 cloth for the most part.

 

Coosa seems to absorb dust like a sponge. My theory has been that its the reason for the adhesion issues. Combination of an air nozzle and and shop vac with diligent cleaning before a layup has been my solution, so far seems to work. Aside from that my initial issues were from not getting the coosa completely wet and getting a dry bond.

 

I used Thermo-Lite board with epoxy and 1708 for my cockpit sole replacement. Thermo-Lite seems to be an exact replacement for Coosa. Their product videos call for a quick sanding with 60 grit and then a blow with air, vacuum, and a wipe with an acetone cloth before lamination. I've done some testing on off cuts and there is no delamination.

 

Thank you for the information on prepping the Coosa. I may sand it, since I got to round off a few corners, etc. Air and vacuum to remove the dust

I did some measuring of the transom to verify a few things . . .


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The underside of the swim deck is parallel to the keel.

The swim deck extends 44" beyond the transom (at the keel). There was some discrepancies in the drawings that I had from the boat manufacturer. 44" is the number.

The transom is a 12˚ slant. The outboard motors generally call for a 14˚ transom . . . no issue there.

The odd angle of the transom inset is 120˚, knowing that I can make the bevel cuts on the joining pieces there, 60˚ each

I'm going to be away for a few days . . . will be back at it next week.

 

Update . . .

I am starting in on fabricating the Coosa board pieces to make up the extension pod. Based of the transom's shape complexity, I used paper to create a template for the mating shapes.

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I just need to verify the bevel angles on the cuts and I should be good to go. There is a 'top' piece the mates to the underside of the swim deck. I figured I could get reasonable dimensions for that piece with some basic measurements.

My understanding with cutting Coosa is that the fiber content can dull normal blades fairly quickly. I got some carbide tipped blades for the various saws that I'll be using.

 

You've alread done the jigs, for future reference a friend got us going on ripped hardboard strips and a glue gun. Hardboard is about 11$ from Lowes and cut into 3/4 inch strips is the fastest jig method weve found for complex shapes and curves. Might have a few done up in the garage, it moves fast and holds a better edge than paper.

Coosa does dull blades, but continues to cut coosa fine for a long time. Your just not cutting anything other than foam with that blade afterwards. We ripped a sheet of 1 inch for beams and then attempted to make a small cut in some thin ply.... used hacksaw blades advance quicker. Ive got a dedicated fine tooth blade that gets coosa abused.