Swapping power head units or midsection lower units or swivel transom mounts between Mercury 83 50 HP 4 cylinder and 93 40 HP

[sjpitts]

So I have a 1983 Mercury 50 HP 4 cylinder outboard, but I have just about decided that I really want an outboard with BIA transom bolt pattern and power tilt and trim that mounts between the BIA transom mounts to be fully compatible with a hydraulic jack plate I have. Next I found a guy with a 1993 40 HP 4 Cylinder with no compression in one cylinder.

What I want to know if there is some reasonable way to combine my working 83 power head unit with the BIA transom mount and power trim unit from the 93. So I am wondering if I could:

1. Transfer my good 1983 power head unit to the 1993 Outboard
2. Transfer the whole midsection/lower unit from the 1993 to the 1983 (that might just be saying the same thing a different way)
3. Transfer the swivel and/or BIA mounts and tilt trim cylinders from the 1993 to the 1983 Motor.
4. Some other way?

Are any of those options reasonable? Which is easier or better?

Or should I just--

5. Sell everything and buy a good Mercury 50/45/40 with the BIA pattern transom mount and power trim I want.

Picts below of my good 1983 50 HP head unit, the bad 1993 40 HP, and the BIA power tilt trim I want on whatever motor I use.

 

[jimmbo]

Have you checked out any Parts Catologs to see if there are any Parts of the Motors that are in Common?

https://www.marineengine.com/parts/mercury-outboard/

 

[sjpitts]

Have you checked out any Parts Catologs to see if there are any Parts of the Motors that are in Common?

https://www.marineengine.com/parts/mercury-outboard/

That is a good question. I took a look at some of those part diagrams, and I did figure out that the power head gaskets (8 and 9 in these two diagrams) are the same, and the exhaust gaskets (26 and 10) are the same, but the actual adapter plates (number 1 in both) are different.

That is as far as I got.

 

[sjpitts]

And looking at the problem from the other direction--

The bumper plates (6 and 10) and the bolts (7 and 19) that attach the top of the swivel bracket are the same.

And the yoke ( 13 and 7) that attach the bottom of the swivel bracket are the same

It really seems like just swapping the swivel bracket/transom brackets from the 93 to the 83 would be the easiest, but when I google this it seems like that is still pretty complicated.

 

[jimmbo]

What about 5 and 9? They appear to have a different shape, so Clearance with the Cowl might become an issue?
You have to pull Powerheads to undo the upper Motor Mounts, so 6 of One, 1/2 Dozen the other

 

[cyclops222]

At 20 years old I changed a lot of parts from different engines.
In my head.
Had a great marine mechanic near by. He did conversions with parts prices. And cost to unscrew up, if I ran to trouble. I could put the pistons from a Rolls Royce 2200 hp engine into my Evinrude 30 hp.
All mental B S dreams.

 

[sjpitts]

What about 5 and 9? They appear to have a different shape, so Clearance with the Cowl might become an issue?
You have to pull Powerheads to undo the upper Motor Mounts, so 6 of One, 1/2 Dozen the other

I think you are possibly right about 5 and 9. I didn't think of that.

I am not sure what you are referring to as "upper motor mounts". Where are those?

 

[racerone]

Some of the different parts are due to the difference in the cowlings.----Which cowling set -up are you going with ?

 

[jimmbo]

I think you are possibly right about 5 and 9. I didn't think of that.

I am not sure what you are referring to as "upper motor mounts". Where are those?

The Bolts 7/19, are bolted to the Upper Mounts which are hidden inside the Exhaust Plate Extension, with is between the Block and Driveshaft Housing

 

[sjpitts]

Some of the different parts are due to the difference in the cowlings.----Which cowling set -up are you going with ?

I would do either cowling-- whatever is easier or better.

The only thing I really care about is the BIA mounting and the power tilt and trim that goes with it. And an engine with good compression in all four cylinders.

Although maybe I should research this--- I don't know if there are other differences between the 83 and 93 that I should consider. Are the electronics more reliable in one than the other?

The 93 does include oil injection that the 83 does not-- but I have had multiple people tell me that Oil Injection in an older outboard is unreliable and should not be used. And maybe that is why that engine has low compression in one cylinder.

 

[jimmbo]

If one cylinder is bad on your Engine, I doubt the Oil System is the Problem. It is not Oil Injection, it is a System where Oil is added to the Gas before it gets to the Carbs, so all Cylinders would be Oil Starved and Damaged
Some will Insist that the Oil is Injected into the Gas, so, Oil Injection

I think you should be able to just swap the Powerheads. Both are 44 in. 4 cylinders.

 

[redneck joe]

Oil injection is a Chevy Ford Dodge discussion. I personally want less systems that can fail so even if I had one I'd disable and premix. There is a semi current thread about it that contains the usual arguments.

 

[jimmbo]

Oil injection is a Chevy Ford Dodge discussion. I personally want less systems that can fail so even if I had one I'd disable and premix. There is a semi current thread about it that contains the usual arguments.

Often the Operator fails to add the Oil or adds the incorrect amount, or fails to adequately mix it...

 

[redneck joe]

Often the Operator fails to add the Oil or adds the incorrect amount, or fails to adequately mix it...

Can't argue that at all as one who has forgotten the plug multiple times as recently as last year and have lauches a boat to the ramp twice as recently as three years ago. Human error is prob 70% of the failure.

 

[Faztbullet]

Power heads are the same, just a lil updated on electronics...swap and go