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‘78 Merc 110 (9.8hp) carb rebuild

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PeteM

New member
I’m working on my Dad’s old Mercury 110. It hasn’t been run in a few years and wasn’t stored properly. Also, it was “serviced professionally” the last summer it was used, and it never ran quite right after that. I’m comfortable getting my hands dirty wrenching on engines, but I’m not especially familiar with outboards. I pulled the float bowl and it was all full of crud (varnish and some pretty crusty solids). I’m working on rebuilding the carb now. It’s the type with the integrated fuel pump. I picked up a full rebuild kit and I’m working from an old Mercury service manual. I’m going through the disassembly and I have a few questions.

First, the kit came with three tiny brass plugs. I can only find two of these pressed into holes in the carb body. Is there a third one someplace, or did they just put an extra one in the kit? Should I try to extract these plugs for cleaning or leave them alone?

The service manual lists an “Inlet Needle and Spring”, but there doesn’t appear to be a spring shown in the figure. There was no spring present when I disassembled my needle-and-seat (the one controlled by the float). Is there supposed to be a spring?

I’m sure I’ll have more questions as I go, but this is good start. Thanks in advance for your help.
-Pete
 
There's lots of parts in that very expensive kit, many that don't go on your particular motor. (The idea is to make one, universal kit.) Some carbs use the spring, some do not so don't sweat that. Since there was so much crud in there, you need to blow out/ poke out all tiny passages, such as the idle tube.

Jeff

PS: Those are overlooked, excellent motors!
 
I need a little more help. I finally got the carb rebuilt and installed. The engine started on the second pull! But there was no water from the tell tale so I shut it off quick. I checked the impeller and it was shot. I put a new impeller in today and fired it up - still no water coming out. What should I look at next?
 
I pulled the hose from inside the housing and blew some air through it. Air flowed through fine - lots of bubbles down in the water. I started it up, and water flowed out great for a few seconds, then stopped. I shut it down, blew some more air in the hose from the top, fired it up, and the same thing happened. Water flowed for a few seconds, then stopped. Maybe a piece of debris (old impeller?) is lodged in the tube somewhere? I’m pulling the lower unit to inspect now. Let me know if anyone has further advice.
 
Pull the tell tale fitting off the block and start it and see if it does the same thing? You can run it a couple minutes safely just put your hand on the cover the plugs go through. Shut it down if it gets too hot to hold your hand there.
 
When I tried my '77 7.5 this spring, it only peed at higher speed. I ran it in a strong mixture of Salt-Away in a garbage can . That worked. The motor is made up with parts from a '77 and a '76. The '77 was a local, B.C. salty with a seized gearcase and the '76 was a Ontario freshy with a blown powerhead. The 75 (7.5) and the 110 are basically same.

Congats on getting the carb back together right.
 
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