'71 Merc 115hp outboard - couple issues

Kizzelwhix

Recruit
Joined
Jul 29, 2010
Messages
1
I just traded my bike for this boat - My first boat. I'm extremely mechanically inclined but so far, have not ever messed with a boat.

When I bought it, the guy hooked up ears and started it up for me, ran fine, ran great.

got it home, did a quick once-over look, saw nothing wrong. took it to a buddies (who does know a little about boats) and he said first thing we should do is change the gear oil in the lower unit to see what it looks like. thats where the first problem comes in.

Milk

So we change it, put it in the water to see what she can do - thats where the second problem comes in - not much. Runs very boggy once there's pressure on it.

Get it out of the water, gear oil is milk. I know there's something wrong down there, but just for diagnosis purposes I've put it in the water a couple more times for no more than say 20 min just to run it and diagnose this boggy problem. From my experience and reading on these forums I figured it was a fuel issue.

3 carbs and 2 fuel pumps just recently rebuilt, however the carbs were nowhere near syncronized - I could tell just by looking at the jet screws. After some fiddling around, I very un-proffessionally syncronized them (found a setup that ran pretty good, then did the count the turns trick on all the screws across the 3 carbs)

So now it will run great for about 2 or 3 minutes, then start running boggy (from my auto experience, sounds like a cylinder or two isn't getting fuel, or isnt getting spark) - All spark plug and wires look good. Pulled the dist. cap, cleaned all points.

Its still running boggy, and I still have water getting into my gearcase.

So my questions are:

What can I do to diagnose the possible fuel shortage problem?
and
What can be letting water into my gearcase?

As I said, I'm a boat engine noob, so go easy on me.

I should mention I red the FAQ on "Testing your boats fuel system" - and intend on checking for air in the lines tomorrow, then maybe next week when I get paid getting the equipment to do a vacuum check.

its a 71 merc inline 6 (1150 or 115 horse)
 

Coloradolakeboy

Petty Officer 2nd Class
Joined
Jun 21, 2010
Messages
197
Re: '71 Merc 115hp outboard - couple issues

Sounds like you can do all the work. A Merc service manual would allow you to do just that with confidence. Plus, after you read it and some stuff isn't clear, somebody here can help. You are going to have to start from the beginning and assume NOTHING has been maintained. Read the wakening a sleeping motor thread in the repair and maintenance section (before you get here) in the frequently asked question thread.

Fuel shortage... replace all the old fuel lines, bulb, filter and connectors. Air is most likely entering the carbs causing a lean condition. Rebuild the carbs, which means: disasemble, clean like crazy and new gaskets and needle seats. check the floats. Get a spark gap tester and set to 7/16" gap and check for spark. Check for compression, maybe first, before you waste alot of time and money.
 
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