Twin I/O to Twin Outboard Conversion Project

Yes, 200˚F + can be too hot . . . These pieces are getting up to 120-130˚F, so no worries.

 

One insert done and 1 to go . . .
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My newly formulated method is to set up about 16 layers, one at a time, insuring proper wet-out for each layer. Then I use the cut-out piece and some weights to 'squash' the resin/glass flat and allow it to cure. Then I add the remaining 6-7 layers to get it even to the surrounding material. And finally, a larger piece of 1808 to tie it all together.

It sure makes for a heavy piece, but the transom should be indestructible . . .

 

The solid fiberglass inserts are done . . .

Here are a couple of pictures for the folks at home.

In-process . . . rolling out each of about 25 layers by hand . . .

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Here is the completed transom piece . . .


On to the next step . . .

 

I've spent a fair amount of time over the past week working of the choice of engines. I have been mainly looking at 300HP models, but have considered some 350HP as well. My design parameters were for 350HP, so no worries about the bigger engines.

In total, I have 9 price quotes from 4 brands of engine . . . Mercury, Yamaha, Suzuki, and Honda. The Honda BF350 was a late contender, as they are having a sales promotion right now. Quotes are ranging from $117,000 to $88,000. I can get $20K off on the Honda 350's, which is super attractive, as it is the most powerful and at the lowest price. My only concern was the shear size of the engines. So, I did a mock-up drawing to see how they would do.
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They are a lot bigger than many of the 300's and extend further into the transom well. The Mercury 300's need about 24" of clearance vs. the 31.9" for the Honda. The Yamahas need about 26". It looks like the Honda will just touch the swim deck at its full tilt (68˚), but will be well out of the water. I'd be happy with a bigger engine (Honda is 4.95L V8, Mercury is a 4.6L V8) and the others are V6 in the 4.0-4.4L range). Presumably more torque, which this boat needs.

I could have grabbed a pair of 5 year-old Suzuki 350's for not much money, but I did not want to go down that road. I'd rather stay with new engines, since they will be integrated with the latest version of the controls.

 

Stern thrusters would have been an easy add.

 

The honda deal is a massive amount of power for the price with the current rebate.... but its so massive. Wanted one but there was no way to stuff it in my outboard well without almost new boat level reworking.

I do like the glendinning stainless control heads.

 

I have GD controls with two smart actuators. Pretty flawless thus far.

 

I think it was good for honda to work with them on the ist controls. Would think it would make optimus integration fairly straightforward as optimus works well with glendinning.

10k per outboard in rebate is non trivial money..... if they can be made to fit.

 

It looks like the Hondas (with the iST) integrate well with the Optimus vs. the Suzukis, based on the pricing I got. If I go with the Honda engines, I'll have to make sure the transom can support the bracket footprint and modify things accordingly.

 

I ordered the engines . . .
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Honda BF350A 30" Silver (350 HP 4.95L V8)

Optimus 360 Joystick System

A bit bigger than I had planned, but with boats, nobody says to "get a smaller engine".

With the V6 engines (Yamaha & Suzuki) I was concerned about the low-end torque. The Honda engines would be no worries.

 

A quick note about the larger engines . . .

My original design parameters were 700 lbs per engine and 350 HP worth of thrust. The Honda 350's come in at 775 lbs for the 30" shaft models. I re-ran my calculations with 800 lbs per engine and the 350 HP including the safety factors. The forces on the bracket structure will be about 6% higher and the localized forces on the transom will be 2% higher. The actual fiberglass laminate schedule is even greater than what the original calculations required.

So, no worries from a structural perspective.

 

I think rewording that as "...no calcuble worries from a structural perspective." may be more appropriate.
But, what do I know.
Carry-on.

 

Progress update . . .

I have almost finished off the glass work on the internal structure and surfaces. One more thing to add, moving onto the transom area.

 

I added the gussets on the inside of the planing surface and also installed the transom.
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Splashwell areas . . .

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Next up will be fillets and then tabbing of the transom to the stringers.

 

Transom Update . . .

I ran a couple layers of 1808 where the top plate meets the transom. This should provide a very positive hold on the top of the transom. A bit of an unusual approach, but I planned to put a 1/2 top-cap on the transom, but I wanted the glassing to go under it in those areas.

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The top cap is 1/2" Coosa - to be rounded.
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Here is the top cap rounded and a layer of 1708 over it. There will be quite a few more layers as my target thickness for the transom is 0.45" of glass each side, yielding ~ 1.9" total thickness.
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In another thread, I asked about 2415 cloth vs. 1808. I got 8 yards of 2415, so I thought to try it . . .
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It lays flatter than woven roving, as the bundles of glass appear to be flatter than what you get with woven roving. Anyway, with WR and often bi-axial cloths I apply a faint layer of spray glue and adhere 0.7 mil plastic sheeting so it is more manageable during measuring, cutting, and layup. Once the resin soaks through from the backside the glue is no more.
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Here is the 2415 as a final layer of tabbing.
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It uses a little bit more resin (per sq in), but not terribly so. It appears that the resulting thickness is about 2X the biaxial cloths, so it is good for bulking up.