Mercury I6 Powerhead ID

[Nateshoe]

Recently purchased a boat w/ a claimed '78 90hp mercury lower unit and a '86 115hp mercury powerhead. I am attempting to confirm what powerhead it is. Welsh plug on block shows A149297. Intake stamp is 9718435. Serial no. on transom mount is 5034059. Any help would be greatly appreciated!

Thanks,
Nate

 

[Chris1956]

The Maxrules web site has a model year guide for Mercs. That should ID your powerhead. As for the gearcase....a '78 gearcase will have the straight down trailing edge on the skeg. The newer gearcase will likely have the swept back skeg.

 

[Nateshoe]

Yes I checked there first. Confirms that the lower unit is a ‘78 and power head is an ‘85 (not an ‘86). How to decipher power rating of the power head though? Serial number on welsh plug means is could be an ‘85 115hp or ‘85 90hp. Maybe I’m missing something

 

[Chris1956]

Block part number should tell you that info. It used to be stamped (moulded?) near where crankcase and crankcase cover bolt together, on transfer cover side. Check Crowleymarine parts list for both 115 and 90HP models of that year.

Block serial number should also tell, but I am not sure what site to look at.

 

[racerone]

Carburetor jet size may offer a clue as well.

 

[Nateshoe]

8311 on the block so looks like a 90hp. Got hosed on this one, live and learn I guess

 

[roscoe]

I have a similar issue and can't seem to locate that number.
I just spent 15 minutes looking for it.

Could you perhaps show me exactly where the block number is located ?

Thanks.

 

[Nateshoe]

Just an inch or two below the welsh plug on crankcase

 

[roscoe]

thankyou

 

[roscoe]

OK, well my main motor is 8310, 115.
Spare parts motor is 115 as well, but doubt there are many part I could use.
The other almost complete motor, (missing solenoid and cdI) is a 90 as labeled, but is an external tilt pump model.

Thanks for the help.