1979 Mercury 115 HP, inline 6 carb help

[biggjohnjeremy]

Hello everyone, today I have bought my first boat. Its a 1979 as far as I can tell with a 115hp Mercury inline 6. The "tower of Power" I have come to find out. Anyways I wanted to start with the fact that I have a decent history of wrenching on motorcycles but no experience with boat motors, so I have a ton of learning to do. I am excited about this new journey, and I need some help from the Iboat Community to start me in the right direction. Ive done some searching and havent found the info I need. For starters, I picked this boat up in decent condition for $700 from a guy who parked it after he broke his back and its been sitting for around 2 years. The gas tank still has gas in it that has since gone bad. And he was able to run it off of an auxiliary gas tank about a year ago, but a friend of his tried to start it with the bad gas and now the carbs need to come off and receive a good cleaning. Also it will probably be good to do an oil change before putting it on the water.

What I Need to know is how Difficult are these carbs to take off and clean? Will I need a new carb gasket kit, and if so can I get links to some? I dont trust my knowledge on how to identify the parts well enough to be sure I buy the Right ones. Also if anyone had a used service manual they would sell me, that would be AWESOME. Or maybe a link to one on the Internet would also be Fantastic.

Thanks,
NOOB Bigg John

 

[merc850]

You can get manuals here http://store.oldmercs.com/category_s/2109.htm. I would first replace the waterpump impeller then at the same time the LU gear oil, after this check for spark with a timing light on a plug wire; a trick I use to check the fuel system is tilt the motor onto the locks at the side then pump fresh gas into the motor and it should run out of the carb throats and help loosen the floats. It will help you decide whether to mess with the carbs. You'll also need muffs to supply water to the motor from a garden hose - don't run it without them.

 

[Chris1956]

The carbs are pretty simply. They are tricky to remove, however. You will need to remove the wrap cowl, top cowl, top and front cowling support, choke wire and starter. Disconnect the battery as well. Remove the three carb bowl covers as a unit. The middle and bottom carbs will come off easier than the top carb. The top carb has a lever connecting it to the distributor. It will wiggle off.

Remove the brass hex plug to clean the main jet. Remove the top brass plug to clean the idle restrictor tube. There are three pinholes in the carb throat, for the idle circuit. Make sure they are clean. Replace all gaskets, inlet needles and seats and floats. Adjust per the service manual.

 

[tavacska]

It took me 2 days to remove the carbs the first time.

But now it takes me only 15 min to take them off.

 

[biggjohnjeremy]

OK thank you for your responses. I am in the process of getting a list of parts together. So far I'm getting a water pump rebuild kit, fuel pump rebuild kit and 3 sets of carb rebuild kits. If there is anything else I shold probably go ahead and replace in yalls opinion, please let me know. I wanna try and be on the water by memoral day.

Anot her question I had about the motor is that when I got the ear muffs and put them on the LU, the water didn't seem to be going anywhere. It just flooded out the sides of the muffs... nothing coming out of tell tail hole or the prop. What should I be looming for?

 

[Chris1956]

Carb kits don't always come with floats. Make sure you buy carb gaskets, inlet needle and seat and floats.

Water should be sucked into motor initially when you start the motor. Some water will always escape from flusher, when the motor is idling. Water should exit gratings above antiventilation plate, and maybe thru prop. The telltales clog easily.

 

[racerone]

?-----Vanes in the pump will block the flow of water if the motor is NOT running.

 

[biggjohnjeremy]

So if the motor isn't running, there won't be any circulation of water? That's good to know. I was turning it just see if it would start with only fresh gas in it. But no, I only saw gas dripping from top carb. I'm in the process of getting to the carbs to remove. Will I need to take off this coil to get the bottom one out? And do I have to take the starter off too?

 

[Chris1956]

Gee, my post #3 tells exactly how to remove carbs....

 

[biggjohnjeremy]

Gee, my post #3 tells exactly how to remove carbs....

I for sure read it, but as I was in the process of taking them off I didn't see why the starter needed to come off. Juse a few hours ago I got them off and am now waiting on parts. When I get to taking them apart should I be aware of any set screw or tuning screws I should count rotation of?I saw one, but is there any other tuning screws I need to be looking for? And I think there are 3 brass caps or screw's that have some sort of red sealer on them. Can I leave them be, or should I take them off and really seal them with loc tite? Thank you for taking time to repond

 

[biggjohnjeremy]

BTW I went back and got new floats, that was a good call that I didn't notice they don't sent with the kit. I can't than yall anough for helping me get a grasp of this motor. It's been helpful. Although I'd like to clarify where this anti ventilation plate is that you mentioned? And also be sure that when I had the muffs of without the motor running, the water shouldn't be going anywhere at all, right?

 

[Chris1956]

You need to clean the main jet and idle restrictor jet in the carbs, as well as the idle circuit. Thye main jet is under the hex bolt at the base of the bowl. Blast it with gumout. On top of the carb is a brass plug at a 45* angle. That covers the idle restrictor. Remove it and blast the idle restrictor jet.

Blast the idle air intake in carb throat and see the stuff come out three drilled holes in the throat.

Seal the plug with wifey's nail polish. It is best to use her favorite polish for this!

Or if not that brave, use some silicone caulk.

After you clean the carbs, set the idle mixture screws to 1-1/2 turns open. You will need to adjust them manually, in the water, motor warm and in gear to complete the repair.

Antiventilation plate is the horizontal plate above the prop. It should run on the surface of the water, and helps keep the prop from sucking air.

If the motor is not running, it will not allow water to circulate, when using the flusher.