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Been toying with the idea of mounting a 90 etec to a 15" mid and nitro lower for a while. I have a blown 75 etec here I was thinking of just switching to carbs and making something crazy out of but if anyone can find me a 90hp ecm, I'd kind of like to try that and see how it works stock with the short mid and nitro lower

Kevin

Kevin
I have been thinking along the same lines as you but it will be a long project. I have had an adapter plate cast up similar to the ones you make for the OMC SST 60. Have a E-Tec drive shaft which I found out is a bigger diameter than the 3 cylinder OMC, so I will have to think about the water pump end. I have a guy that can adapt the E-Tec drive shaft to the 3 cylinder OMC bottom end. This guy has already made a couple of SST 60 drive shafts for me. I have a Long Shaft mid section for the E-Tec and intend to take a silicone mould off either side up top and then make a 2 pack foam pattern that can be adapted to the SST 60 midsection. I have already taken a silicone mould of the SST 60 midsection and made a foam pattern. I will cut and shut and form to a reasonable shape. There is a local foundry near me who will be able to cast up the midsection but that will be some time away. Still in thought mode with a bit of sorting out to do.

Stephen Medaris

There is a company called Bay Manufacturing they manufacture 5 inch drive shaft extensions for the outboards. One way to keep all of the original water pump etc. would be to buy the extension for the E-TEC and then machine the other end of the extension for the gear case drive shaft. I have done this matching a 90 to a 70 Yamaha. You can even use a pin to join the two. A real advantage is you can reuse the connector if you need to replace the gear case.

The plan was to make an adapter to slide over the end of the drive shaft like Hounddog mentioned. Even if I have to cut it shorter, I can still mill flats on the drive shaft to make it square and slide and adapter over. The 3 cylinder mid doesn't really have the room to put the etec powerhead on with an adapter plate but the 2 cylinder one has more room to fit the tuner and everything in. I just need to draw up the bolt pattern and everything from the etec and make an adapter plate and tuner for it to go on the 2 cylinder mid. That's kind of what I had in mind anyway

Kevin

For those who do not have a machine shop and only want to do the adaptor once here is how I did it. It helps if the powerhead drive shaft is larger than the gear case. Some gear cases are cheap compared to others and some perform better. The gear case you use must have a water pump capable of cooling the powerhead. On the 90 hp Yamaha the small 55 hp Yamaha bolts right on and the pump is fine. The drive shaft of the 90 is much larger. You mount the 55 on either a 15 or 20 mid. You can use a long shaft 55 for both mids.
Both ends of the 90 extension are the same spline.
When your finished it must line up perfect.
I cut the top 4 to 5 inches off the junk 90 drive shaft.
The machine shop used a lath and made a hole in it the same size as the 55 hp drive shaft.
I cut the 55 drive shaft to the proper length.
Inserted it into the drilled sleeve of the 90 drive shaft.
To pin it you can go thru the sleeve or go thru the extension and the sleeve which is stronger.
To replace the gear case after that. You remove the pin, cut the new gear case drive shaft the length put it in the adaptor and drill a new hole for the pin.
I am sure there are other methods, but this works.

Are you saying the 55 shaft fits up into the 90 shaft that's been Bored out to exact size. ?
what is the diameter of the 55 shaft and what diameter is the 90 shaft.

It was several years ago that I did it. The 90 shaft is larger and the 55 does fit inside it. There was not a lot of meat left so the 55 shaft did not go all the way to the top and I did file the 55 shaft down a bit to fit.
Remember it is the thick walls of the extension and the pin that make it strong.
The pin was made from an ARP rod bolt.
What other people did was weld the top of the 90 shaft to the lower portion of a junk 55 crank. They cut the 55 shaft to length.

Here's an idea, what if you took the bottom of forge crankshaft from an early 56er or a late Stinger to make your shaft adapter, have it machined out and splined to E-Tec specs.

If you were mounting a nitro case on a 20 inch e-tec to try it provided it bolts on, you would use a 15 inch nitro. You use the lower portion of a 4 spline crank and weld the correct length top portion of the e-tec driveshaft. If it does not work you have not hurt anything. Tough part is finding a junk e-tec drive shaft.

When I bought my first Stinger, it was converted to a long shaft, the guy told me his father was a machinist and did it all himself. The shift rod was extended with a small 7" long threaded bushing, he lengthen the water tube with a piece of copper tube and coupling, the drive shaft extension was all machined out of one piece, no signed of welding, not sure how he cut the internal spline but theirs different ways to go about it, the mid was lengthen at the very bottom between the mid and the gear case with a fiberglass casting. I have to admit that he did a good job but at the time it was more like what the f...k, why would you do this to nice little short shaft especially that they are getting harder to find.