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Identify Year and HP by serial number

T

thebubba

Regular Contributor
This forum has really been helpful, Thank you in advance for your help. I have one more motor to identify. I looked at the Mercury charts and cannot find it. Here is the SN that is checked and double checked A172118. I think is about a 1986 7.5HP. It seems that other A serial numbers were 1986. Please help, I need to get a manual and replace the impeller.
 
Thank you so much for your help. This forum and all the members have saved me many times over. Hats off to you all. Now I will order a manual and a new impellar and have a great trolling motor for my boat.

Best Regards,
 
So I am having difficulty looking up parts by my serial number. I finally found a website that took my model number 1007205. I am looking for an impeller and two were listed. 47-89981 and 47-89980. They are different dimensions so I assume they cannot be interchanged. Any help would be appreciated.
 
Just take the old impeller out !!---Most have a part # on them ----------then order the new impeller.--------------Or measure the diameter of the shaft where the impeller sits and post that value.
 
So I finally got around to removing the impeller to look for the part number. This motor is the easiest to change an impeller on I have ever seen. You just take off two nuts and the lower unit slides right off. The shift linkage just separates on its own. I had it off in less than a minute. The part number was right on the impeller between two fins. 47-89980. The older impeller was still intact, but almost every flap was torn and it was stuck in a deformed way when I removed it. Also two large junks of carbon like material came out, which would have clogged the water from circulating at all. These definitely need to be replaced every couple of years at a minimum depending on use. I blew out all the lines and did not find any obstructions. I know when these impellers come apart they can clog things up. Luckily I bought this engine before it happened. I also changed the lower unit fluid while I was at it. It was dark black. Obviously this motor has seen some use without any maintenance. Once I put it back together we will see if the carb needs some attention. I love saving motors from abusive situations and bringing them back to life, this one should be easy.
 
It is possibly the worst / shortest lifespan impeller in outboard motor land.------Like I said you will find the number on there.
 
So I replaced the impeller, blew out the lines that I removed and tried running it. Still no water pumping. I opened up the flush port and a bunch of tiny white little pebbles came out. It still doesn't pump water, so it must have some pebble clogging the motor. How do I clean out the motor ports on this engine so water will circulate? When I run the motor briefly I can feel exhaust coming out the pee hole.
 
On severe overheat on these you may need to remove the powerhead.------------There may be a plastic washer around top of the water tube.-------It melts and block water supply to the engine.------Replacement is better material for the job.-----------Or make your own.
 
So I finally got back to this motor. I have had a cold and the weather turned from fall to winter here in a hurry. As I took it apart this time and really studied the lower unit and how it connects in with the motor, I realized the water tube may not be engaging into the powerhead at all. The water tube was coming out with the lower unit, so When I assembled it I assumed it would just go back together correctly (never assume anything). I pulled the water tube out of the lower unit and with the help of a flashlight put it into the hole in the bottom of the powerhead and slowly slid the lower unit together making sure the water tube went into the impeller housing as it fit together. I had some difficulty getting the main shaft to find the power head hole, but finally after some gentle struggling and walking away for awhile it slid right together without any issues. I made sure to apply a little grease on the ends of the drive shaft and shift shaft so they will come apart again some day. Now I just need to tank test it this weekend to see if it pees water. I posted this to help others with a similar motor not make the same simple mistake I did. I will report the results. Once it is pumping water I may need additional help to get her running perfectly.

Does anyone know if this model has a thermostat? I cannot seem to locate one. I can post a picture later if needed.
 
A thermostat would be right above the exhaust cover.------A spring affair keeps the cover on , makes it easy to inspect / clean out / replace.
 
The cold weather has slowed me down, here is an update. This unit does not have a thermostat, but some models like this one do. I got it out in a barrel and started it up. It pumps water like crazy now. It is amazing what happens when you connect the copper tube correctly. It seems to run pretty well, but every now and then it misses. I am thinking it may need a carb cleaning to get it running smoothly all the time. I did a compression check and get 98 PSI in both cylinders. I still need to make or get a spark tester. The carb is an easy thing to start on though.
 
Some forum members don't like my method of simple carb cleaning. :confused: It works well on a fuel gummed carb that is not flooding. Just remove the fuel hose at the carb and shoot Seafoam spray w/a nozzle into the opening and fill the carb. Let it sit overnight and run it the next day. It will smoke like crazy but the interior of the carb will be clean and throttle response will improve greatly.
 
I hope you are able to assist. I have just bought a boat with a Mariner 90hp 2 stroke (3 cylinder). The seller had no information on the motor whatsoever.
I cannot find a serial number plate anywhere, I have looked on the transom as well.
The numbers I have found are:-
On the block – 42885-C2
On the side engine plate – 832753A6 1567
On the starter 50-66015 (also a date stamp of 07/15/1997)
Bottom rhs of engine 993352
854515 1347 on what looks like the solenoid block.
And also:-
MA-90-ELPTO
7090412GB
Are you able to identify the motor from these please?
 
Here are the results of filling the Carb with Seafoam. I drained any remaining fuel out of the carb through the drain screw, I removed the fuel line and filled the carb up with spray in seafoam. I wasn't able to get to it the next day so it sat for two nights soaking. I hooked up the fuel line pumped the ball and it fired right up smoking like crazy for a few minutes and ran smooth as a baby. It now idles down without missing, and responds well to a quick throttle up. In my situation the sea foam trick worked extremely well. Thank you guyjg for the idea! I didn't have to buy any parts this time. By the way, this motor hasn't been started since 1995. It was given a full tuneup with new coils, points, spark plugs, and a carb tuneup then, but that is a long time to just sit without running. It runs great now.
 
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Sorry, I got my motors confused (or my posts confused rather), I tried this on my 1968 Evinrude 9.5 hp, which I also have a thread for under Evinrude/Johnson. I do also have a 1985 Mercury that I have been working on, which I will try this on the Mercury too this weekend.
cleardot.gif
 
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...this motor hasn't been started since 1995...filled the carb up with spray in seafoam...it sat for two nights soaking.
Click to expand...

The long soak was needed. Amazing stuff that Seafoam. I use it in the fuel supply for every gas powered toy I have--never had a gummed up carb. Glad it worked for you.
 
Looking for a download of in particular the lower gear case and how to dis assemble it.

Mine is stuck in gear so I need to sort out what has gone wrong.

Thanks
Jeff
Loving owning of Four "Gnats"
 
I realize the post should have been a new topic, but yesterday this damned site would not let me add new topics, so I had to add to an existing one.
 
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