swap cobra drive for alpha I

Great sight, lot's of info. I picked up a project boat, a 89 Renken seamaster 22'. The hull and transom are in good shape but needs a new motor.... It had a 4.3 with a cobra drive. I would like to replace it with a 350 with a alpha I drive. I'm guessing I need to remove the transom assembly? I have seen kits adapting cobra to fit alpha outdrive. It seems there are plenty of used units on the market and I think it would be better to go with a mercruiser drive system. How difficult is it to remove the cobra and replace it with the alpha? Does it require any major transom modifications? Any info would be great, thanks matt

Re: swap cobra drive for alpha I

If I'm not mistaken, I believe that year of OMC used the same keyhole as the Mercrusier. If you buy a complete Mercruiser transom assembly then it should be an easy swap. At that point you may want to also consider a brand new Sterndrive engineering outdrive as well.

Re: swap cobra drive for alpha I

Here is the kit to adapt the Alpha I Gen II outdrive to the Cobra transom shield.

http://www.sterndrive.cc/mm5/merchant.mvc?Screen=PROD&Product_Code=9D-116&Category_Code=Cobra

There is nothing wrong with using your transom shield and trim system. To change the transom shield you would also have to change the flywheel cover, Y pipe, exhaust system etc.

Re: swap cobra drive for alpha I

Thanks for the info. I'm leaning to the conversion kit, it would save time and $. I posted another question in the prop section about trolling speeds with this set up. I was wondering if someone has a similar sized boat (22' walkaround) and engine set up (350/alpha 1) can it run at 1.5-2mph? I know there are plenty of ways of slowing the vessel, dragging 5 gal buckets, ect, but my goal it to set the boat up to be able to run off the main engine when trolling. I know I could use a kicker, but my past experience is that without the main engine running, all the electronics drain the batteries since there not getting charged. If I were to use a kicker could I use a dual lever throttle control to operate both engines? I don't have a good place to mount a second throttle. Thanks for you time and knowledge, matt

Re: swap cobra drive for alpha I

Ayuh,... Keep yer prop questions in the prop forum,....
I answered ya there...

Few to no boats are able to be propped to run properly at wot, yet run slow enough to troll...
There are Many options, without runnin' a kicker...

On my barge, I use trim tabs, 'n drift socks...
I also have a torque-shift prop by Land & Sea...
It trolls at 11" of pitch, 'n shifts up to 'bout 20" at wot...
With the trim tabs full down, I can idle/ troll at 1.5/ 2 mph...
Throw out the drift socks, I get down to Sub-1mph...

Re: swap cobra drive for alpha I

but my past experience is that without the main engine running, all the electronics drain the batteries since there not getting charged.

Click to expand...

A simple two battery system with a selector switch would isolate your starting battery and not run it down, a kicker with a small charging system would help maintain the battery with the depth sounder on it.

If I were to use a kicker could I use a dual lever throttle control to operate both engines? I don't have a good place to mount a second throttle.

Click to expand...

Sure, looks like plenty of room left there for a dual lever control