Replacing 1977 Evinrude 140 with 1995 Johnson 150

I?m replacing my 1977 model Evinrude Cross-Flow 140 HP V-4 with a Johnson 1995 model 150 HP Loop Charged motor and have a few questions.

The wiring harness connector plug inside each motor looks identical to each other including the location of every connector pin. Are these plugs compatible with each pin providing the same function? The control box that?s on my pontoon boat has the wiring harness going into it including the ignition switch and I was planning on using it if possible. The wiring harness that?s on the boat where the newer Johnson 150 came from is built into the boat and I can?t see removing it along with the throttle box and control cables (which are too short) if I don?t have to. Could it be as easy as just plugging in the main wiring harness connector and using my existing throttle and shift cables? The cables look the same but I don?t have them disconnected yet for a complete view.

I know I?ll have to do some work on the power trim wiring but I don?t think that will be too big of a deal but any input on that would be appreciated also.

The Johnson 150 HP is a new motor to me and I tested the compression (with all plugs out) and all cylinders showed about 95 PSI across the board. All of the spark plugs looked the same with very little discoloration. Does this look like good compression? The motor has not been run in a year or so.

Thanks for any help in this conversion

Re: Replacing 1977 Evinrude 140 with 1995 Johnson 150

The control boxes all have the same plug up through the 1995 model year- so the box will work. They changed plugs in 1996. You'll have to check the throttle and shift cable ends on the engine end. The cable ends changed in 1979. The only thing your 77 box does not have is a safety lanyard cut-off switch. Your 77 has a remotely-mounted power trim box under the back deck of the boat. You'll remove it, as the 95 has that box inside the cowling. (The two trim systems are not compatible with each other.) The compression will depend on whether it is a G, S, H model or not. Those were the Intruder models and used the higher compression 175 heads. Somewhere around 1995 or 1996, the factory changed those heads. The bottom cyl on each had a larger chamber and ran lower compression than the two top cyls. That's normal. Had to do with firing temps/reliability, etc.

Re: Replacing 1977 Evinrude 140 with 1995 Johnson 150

Thanks for the reply. It looks like it will swap out fairly easy except for the trim controls. I should be able to find the up and down wires from the new harness and it looks like I could add a trim gauge if I want.

Lower unit - Rebuilt vs Aftermarket:
I’ve got to replace the lower unit and I’m thinking about an aftermarket from SEI or a rebuilt unit from one of several rebuilders. I installed an SEI unit about 3 years ago on my 175 Johnson and it’s been working fine. Does anyone have a rebuilder they would recommend? Any input??

Changing to a long shaft motor:
I would like to change this into a long shaft motor if possible while I’m ordering a lower unit. It’s going on a pontoon boat and although the transom is built for a standard 20 inch motor, I would like to have a long shaft to get down a bit deeper and I could always raise it up from the lowest setting. I saw a conversion kit for one or maybe there’s a lower unit rebuilder that would sell me a unit and whatever else it takes. Does anyone have experience on what it takes to convert one?

Re: Replacing 1977 Evinrude 140 with 1995 Johnson 150

The factory may specify a drive shaft swap and a midsection spacer. It's the drive shaft conversion that's the expense. For inexpensive X-long shaft conversion kits, check out this website: www.baymfg.com

Re: Replacing 1977 Evinrude 140 with 1995 Johnson 150

You mentioned your cables being to short - you should contact these guys for longer ones www.cccables.com