150 Promax Franken Motor Help

[Supermoto65]

Hello!

I sent this in an email to Don but I thought maybe the collective could add some info as well while he is indisposed.

I just bought a 93 Cape Horn Offshore 19 with what was supposed to be a 1994 200 EFI Saltwater Series. I have tons of boating experience with every other type of propulsion but this is my first outboard. When I went to do some baseline maintenance, I noticed the BIG STICKER on the ECU that clearly says 150 Promax and thus began my searching for what the heck I actually have on this boat.


The details:


Supposed to be a 1993/4 Mercury 200 EFI Saltwater Series. The serial on the bracket is not readable so cannot confirm the outside other than the cowl looks like it … I know you can put stickers on anything lol.


Powerhead serial and all clues point to a 1994 150 Promax EFI. OG205168 on the cylinder case.


Pictures below to help but my main questions are:


Can you tell if the lower unit and cowlings are from the 200 EFI or something else? From my limited research …. It is possible to have the 150 powerhead and 200 lower combo .. as they are interchangeable?


Can you tell from the photos if all the Promax parts are correct or if they swapped other components in as well? Looks like oil injection disconnected (not sure if correctly done). A few other wires not connected. Fresh water flush (from 200) gone. No warning buzzers when key turned on. Trim switch on motor does not work … relays just crammed in there probably because they don’t work with that hood/cowl.


I want to order a new impeller and maybe reeds .. and anything else you can recommend for preventative measures as I don’t know the history of this motor. I have a lot of 2 stroke experience (jet skis and motocross) so I’m not a total newbie.


Not sure about impeller ordering … I assume that is part of the lower unit and would need to original serial? Or can you go off the powerhead?



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[JOE54]

cowl is mewer than 95 , lower is old has plastic intake cover inlets, same impeller (89984T4) and top hsing base may be diff though due to older gearcase dont even have anodes, promax parts look correct but you got lottttttttts a work to do , wiring ,hoses

[Supermoto65]

Thanks for the quick reply!

So .. any idea on the age of the lower? I did a little google searching and only thing I found close was a '78.

I hear ya on the work ... Looks like I need the Oil Pump block off kit from what I can see as well.

Wiring - Is that grey wire on the port side regulator supposed to attach to something? I looked at some diagrams and was not sure.

On the below image ... the wire was disconnected from the Fuel Filter bottom. I reconnected and it ran very rough when I put it back in the water .... on the water I removed it and it ran smoother (well .. as smooth as it did before I attached it). Any idea why it would do that? I will be replacing that filter but I don't know what that wire/probe is for ...

[Vandee]

Gray wire hanging from volt reg is for your tach. If the other voltage reg has the gray wire plugged in just tie the loose one up and should be good there.

[JOE54]

early 80s, that shouldnt efect running quality

[Supermoto65]

Thanks! Yeah. I downloaded the service manual and found the wiring dif ram that confirms the grey wire. Also checked out the oil injection system and can see what they did to disconnect it.

There is one wire that I cannot find a connection to anywhere in the motor. The diagram shows it as connected to the trim sender and the tach? It’s tan with a white stripe. Here is a picture. C2E4FA6F-7C29-4285-A631-4A1EC89D4042.jpeg

[JOE54]

trim sender unit only no tach

[SilverFox579]

That downloaded manual may, or may not, be for your engine as genuine Mercury service manuals are only available in paper form.