1983 Mercury 3.5hp outboard repair

[naturelover]

Well, a 1983? (ser. 6243...) Merc 3.5hp has come in for hard starting issue....

Haven't started it yet, but have a couple of questions beforehand.

Will replace impeller, as previous owner told current owner that it was air cooled. Looks like its been hot, guess I'll check compression also. Know the older motors service limit was around 60psi, same for these, or do these have a little more compression?

Guessing it can be accessed by removing gearcase unit from lower unit? What gaskets/seals should I get also?

Eh, after thinking about it, will probably have to remove powerhead because of gearshift I'm guessing..

Its draining out the gearcase oil/water now, along with the flywheel off for cleaning of magnets and ignition coil module. Gas has been drained and will be replaced with fresh mix, along with a new fuel filter and new spark plug.

Speaking of, there is an extra nipple on the carb with no hose attached. What's this for? Its a Mikuni carb, but don't have it off yet for cleaning to see what model...

 

[naturelover]

Re: 1983 Mercury 3.5hp outboard repair

Well, got it apart and came up with a couple questions..

Split the motor from the l/u, don't believe that it was necessary, but hopefully will make it easier to line up.

Pulled the gearcase from the lower unit to reveal the water pump.



Believe to have found the pumping problem...



So, after cleaning out all the bits of the impeller, took out the water pump sleeve to clean out underneath it, and the first question arises.



Not how its supposed to look is it? And how do you replace the seal as it doesn't appear to come out from the bottom, nor does it look to come up out the top? :noidea:

Did find water in the gearcase oil, looks like this seal is what keeps them separated, along with the prop seal. Appears the whole pump is NLA.

Anyway, got the carb apart. Also applied some heat shrink to the wiring from the module to the coil in the spots it was rubbing.

Carb apart for cleaning.



Looked a little closer at the extra plastic nipple, and it goes below the throat of the carb into the main jet passage.

Any ideas what it is?

 

[CharlieB]

Re: 1983 Mercury 3.5hp outboard repair

Hopefully I read this correctly.

Check out item 14, insert, and pressed in immediately before it the seal.

http://www.mercruiserparts.com/Show...r=713&bnbr=9&bdesc=GEAR+HOUSING+(DRIVE+SHAFT)

 

[naturelover]

Re: 1983 Mercury 3.5hp outboard repair

Well, I removed the metal insert cup the impeller rides in, and that is what is underneath it. Does it come out also? Looked like it was all moulded together as one piece.

 

[CharlieB]

Re: 1983 Mercury 3.5hp outboard repair

With a sharp blade carefully carve out the melted portions that are blocking the seal, inspect that metal cup, if it has a line worn in it that matches the raised sealing ring on the side of the new impeller, replace the cup.

Since this housing is NLA it may be a good idea to start checking marine recyclers for a good used housing. When I was in the NW I found a lot of NLA parts available at Sea-Way Marine in Seattle. Seems they learn what is going NLA and start buying up parts and stocking them. Some Merc dealers are tied into Merc parts and can locate stock items at any participating dealership. I may be possible for a dealer that handles a lot of small motors to have one or two still on the shelf even tho Merc no longer handles it. It is worth making a few phone calls.

 

[naturelover]

Re: 1983 Mercury 3.5hp outboard repair

Well, the owner was able to find a NOS water pump and I was able to get it back together with some new seals and such. Will say that the pictures taken during disassembly came in handy for reassembly.

Made a stand for it also. I should have made that a long time ago, makes it so easy to run in the trash can and to work on it.

I did have to plug that extra nipple on the carb, it just runs too lean, and won't start without many pulls. Plugged, it seems to start a lot easier, but still need to do a couple cold test starts. Never did figure out why its there either.

The fuel valve is shot also, so it's just plumbed straight, with a new fuel filter. Might be able to find one where he found the w/p, or could just put an inline valve in.

I did run it for half an hour or so and it runs well and cool, with a nice spray out the exhaust holes.

Course they always run well in the bucket....