Mercury, 90 HP

[Crazyman1225]

I would like to know where to look on this motor to find the numbers , so that I can find out exactly what motor it is? I would like to know so that I can order a repair manual for it. Thank you.

 

[SeaKaye12]

Re: Mercury, 90 HP

You need the serial number. It's located on the engine mount. If you're in the boat facing the motor...it's under the front of the cowling....just above where the bolts mount the engine to the transom.

It's usually really dirty under there..you'll probably have to wipe away a bunch of accumulated dirt to see the plate.

If that plate is missing; or you suspect that the engine has been part-swapped and the mount may not be the same "issue" as the powerhead; the number also appears on the powerhead as well. Not sure exactly where on your particular engine.

Chuck

 

[SeaKaye12]

Re: Mercury, 90 HP

You boat on Twin Lakes Crazyman? I learned to water ski on that lake in the 70's...behind a 45hp Chrysler on an Alpex boat.

The best years of my life.

Chuck

 

[Crazyman1225]

Re: Mercury, 90 HP

SeaKaye12,
I haven't been on Twin Lakes yet. That is going to be one of the places that the SS will be seen on when the restoration is done. It will also be in the Hudson river for stripers. Is that where you still boat? I hear there are some monster trout in the lake, 10#er's plus.

 

[Crazyman1225]

Re: Mercury, 90 HP

Went and picked up another boat and the 90 hp Merc today. A little embarrassed to say that the boat is a fiberglass tri hull, but I wasn't after that part. The Merc is a " 1979 Mercury 90 (DI ) or (D1) , it was a little hard to distinquish. The serial # is 5163895. It has a Thunderbolt Ignition, along with the tilt trim on it. I am going to do a spark test, plus a compression test on the motor. Would anyone happen to know what the compression should be running at? After those two test, I'll set up a water source for it and try to fire it up. Hoping that I won't have to pull the carbs and clean them. That looks like it may be a little tricky. Not the rebuilding and cleaning part, but the removal and installation. Thank you in advance for the information.

 

[Crazyman1225]

Re: Mercury, 90 HP

I tinkered with my Merc 90 today, and got it running. I have a question that I am a little mystified about. On the upper two carbs there are choke plates that close when the button is pushed. Although there is no choke plate on the lower carb, shouldn't there be one on this carb also? The motor ran fairly sweet after sitting for a little over a year. I wouldn't give it full throttle because even with muffs on it and a good water supply, I couldn't find any water outlet coming out of the motor to indicate the pump was working. So I shut her right down quick before it got hot and caused damage. Would anyone be able to tell me where the water outlet would be on it, until I get my manual? Thank you.

 

[narvlebenoit]

Re: Mercury, 90 HP

I have a1981 90h.p. the bottom carb does not have a choke plate.Looking from the back of the motor the pee hole outlet is on the right.

 

[Crazyman1225]

Re: Mercury, 90 HP

Thank you for the information.