Tower of Power 1150 - unknown year - side bowl carbs float-needle valve issue?

[bbuhlman]

Hello,
I am trying to help out a friend with an older Merc 1150, he thinks it is a ’79. He thinks it is the first year for power trim. We cannot find the serial number plate. It has good compression 130~145 on all cylinders. It runs rough and won’t idle. Sometimes you can get it in gear without it dying and it will run at high speed ok. I get spark on all plugs. I discovered this morning that as you pump the bulb gas pours out the overflow on the top carb so I think I have a float / needle valve issue? Also can anyone help me with the year model? Please look at the pictures and thank you.

-Bill

 

[Chris1956]

The cowling is from 1977. Not the first year for PTT. Serial number should be between transom clamp screws.

Rebuild the top carb with new float inlet needle and seat and gaskets. If you see any dirt, get it out and rebuild the other two carbs, as well.

If serial number is not on transom clamp, look on transfer cover side where crankcase meets it's cover. There will at least be a block part number.

 

[Faztbullet]

Tis a 1977 and the first 5 numbers or serial is : 47913

 

[racerone]

Agreed ---decals are for 76 / 77 model year,------It shows typical wiring issues for those years.----Clean / inspect the 3 carburetors.----Install fuel pump kit.-----Install new water pump impeller.-----Eliminate the " back drag " feature on carburetors.------Clean inside of distributor cap.

 

[bbuhlman]

Tis a 1977 and the first 5 numbers or serial is : 47913

Indeed it is a ’77, we found the plate under about 1/8” of grease…4701324

 

[bbuhlman]

Agreed ---decals are for 76 / 77 model year,------It shows typical wiring issues for those years.----Clean / inspect the 3 carburetors.----Install fuel pump kit.-----Install new water pump impeller.-----Eliminate the " back drag " feature on carburetors.------Clean inside of distributor cap.

 

[bbuhlman]

Researching “back drag” feature now and I’ve already cleaned/ scraped the inside of the cap and scraped the rotor. Thank you!

 

[bbuhlman]

The cowling is from 1977. Not the first year for PTT. Serial number should be between transom clamp screws.

Rebuild the top carb with new float inlet needle and seat and gaskets. If you see any dirt, get it out and rebuild the other two carbs, as well.

If serial number is not on transom clamp, look on transfer cover side where crankcase meets it's cover. There will at least be a block part number.

Thank you!

 

[bbuhlman]

Agreed ---decals are for 76 / 77 model year,------It shows typical wiring issues for those years.----Clean / inspect the 3 carburetors.----Install fuel pump kit.-----Install new water pump impeller.-----Eliminate the " back drag " feature on carburetors.------Clean inside of distributor cap.

If I disable the back drag by plugging those ports on the carbs would I have to do any re-jetting? I’m guessing low to midrange would run a bit richer which might be better anyway.

 

[Chris1956]

No rejetting necessary. Actually, I had that exact motor and never had any issue with the backdrag feature.

Just to be clear, the backdrag function routes carb vacuum into float bowl, pulling in outside air. The backdrag jet is a restriction for air entering the bowl, thus creating a small vacuum in the bowl. This small vacuum leans the mixture a bit at high speed only.

 

[bbuhlman]

One more question, do I have to remove all the carbs at once or can I just take the top one off individually?

 

[Chris1956]

I remember that the carbs are a tight fit. I usually took them off as a unit, leaving them connected by the black plastic "straw" that operates the throttle plate. BTW- those straws are fragile and are not widely available. Crowleymarine says then can get 'em.

The top carb is unique because of the yoke that is around the distributor "finger". You should be able to wiggle it loose after the nuts are removed. Carb gaskets are real cheap, so remember to replace those. If you have the original foam floats, those need to be replaced. The original inlet seats were brass and rubber. Replace those as well as the inlet needles.

You need to remove the top cowling support to do most anything on that motor.

 

[bbuhlman]

I remember that the carbs are a tight fit. I usually took them off as a unit, leaving them connected by the black plastic "straw" that operates the throttle plate. BTW- those straws are fragile and are not widely available. Crowleymarine says then can get 'em.

The top carb is unique because of the yoke that is around the distributor "finger". You should be able to wiggle it loose after the nuts are removed. Carb gaskets are real cheap, so remember to replace those. If you have the original foam floats, those need to be replaced. The original inlet seats were brass and rubber. Replace those as well as the inlet needles.

You need to remove the top cowling support to do most anything on that motor.

Thank you for your reply!