1976 mercury 1150 inline carbs!

[Tduv]

I have a 1976 mercury 1150 inline 6 that I just recently purchased with a boat. The first problem I have is that the primer bulb won't stay hard and when I do get it hard the top carb leaks gas. Is this calling for a carb rebuild? If so do I need a whole rebuild kit with new jets and such or Just the kit with new gaskets,washers and float needle? Lastly, it takes about five minutes to get going and when I cut it off for about ten minutes, it's hard to start again warm. Is this also due to dirty carbs? The guy I bought it off of must have been running like a 3-1 mix for the gas, as when I pumped the old gas out it was almost black!!! Guessing that probably gummed up the engine pretty good. Lastly what reasons would my gas gauge automatically goes to 3/4ths a tank when I turn the boat on no matter the amount of gas in the tank? And my rpm gauge does not read right as it will stat around 1000 rpms at idle then I rev it and it goes up to 2000. When I back off the throttle and back to idle the gauge sticks at 2000. What could be the issue?

 

[Chris1956]

OK, first things first. Get 3 gaskets sets, three floats and three inlet needles and seats for the carbs. Should be $50 or so. Now disconnect the battery and remove the top cowling support and rear cowling support. Now remove the carb bowl covers as a unit. Now the carbs will come off, after you wiggle them past the distributor levers. Careful not to break the plastic throttle levers that connect them.

Clean the carbs up well. Install the new inlet needle and seat. Set the carb float height and install the new float and gaskets. Set the idle mixture needle to 1-1.2 turns out from light seating.

You will need to adjust the idle mixtures on the water, in gear at idle speed.

The gas gauge and tach are electrical. I would ask you to inspect the wiring on the motor. Most harnesses are bad by now, unless replaced.

Also the gas gauge and tach could also be bad. They do not last forever.

 

[merc850]

A compression check is the first place to start. 120psi or so and each cylinder should be within 10% of the others.
You have to remove and dismantle the carbs before you can decide what has to be done; carb rebuilds only usually involve the floats, needle and seat; setting the lever heights and cleaning in mild cleaner. Replace the fuel pump diaphragm(s) and clean the fuel screen on the starboard side of the engine.
The bulb problem sounds like a leaking check valve in bulb. Sounds like the tach might be fried.

 

[Tduv]

Thank you for all the info!! So what I got out of that is I don't need a complete rebuild kit just the gasket one that comes with the needle? Then obviously the rest that was listed. Do you by chance know the measurements for the the levers that hit the needle? Also, for the harness if I remember correctly it only has 6 prongs that connect to the motor. I can't seem to find one like that. Is there anything you may recommend? Thank you again for the detailed response, and a huge thank you on how to easily get them carbs off without having to remove the distributor or the starter!

 

[Tduv]

Merc850. Did the compression. I have 125-130across the board except my #3 cylinder is at 95 . I know it's a bad thing but I'm hoping with a good decarb of the cylinder it should free it up. Like I said the guy before me was running like a 3-1 ratio on it so I'm assuming it's pretty gunked up. If not, is it worth it to put the money into this motor? As everone I talk to says it's a great one. Or do I just clean the carbs and save the cash and run it till its kaput?

 

[jimmbo]

A 43 yr old motor... While I love the inline 6, there does come a point where it can get very expensive to keep it running. For whatever reason, Mercury chose a wire brand with an Insulation that tends to decompose. Parts like Pistons are priced quite high, at least here in Canada. I think they are trying persuade those trying to overhaul, to purchase a new 4 stroke

 

[racerone]

95 PSI is a red flag.-----Remove bypass cover to have a look at that piston.-----Great motors when they are running properly.

 

[Tduv]

I found a brand new power head, not a rebuilt one for the motor for about $1300. Is that a good deal. Guess I got some contemplating to do here.

 

[merc850]

So you don't have the control box/wiring how did you run the motor? I use Mercury's Power Tune to clean a motor's insides (decarbon) and exterior, safe on plastics and paint and very effective.
The carb settings are:

 

[Tduv]

Merc850.No I do have a wiring/control box. I was saying to find a new one might be stuff. But think I found on on the website. Oldmercs.com. thank you for that diagram!! Gonna buy a manual right now for the motor. I'll upload some pictures of the motor to help with questions as in i don't remember seeing a fule pump. Looks like it's two small pumps mounted on the side of the motor. That kind of threw me through a loop. Guessing those are what I would need to clean up as well, if they are actually my pumps.

 

[merc850]

The fuel pumps are between the fuel connector on the lower cowl and the carb fuel lines.

 

[Faztbullet]

You can find a later model motor for what your fixing to spend on that motor. It going to need a $400 trigger to go with that new powerhead.

 

[Tduv]

Just wondering if this kit would work for my 1976 1150 inline 6?