80’s 45hp dies after short time running!!!!

[Newtlaw88]

evening guys,
so I have a 20’ pontoon with a 45hp powertrim motor. Three months ago the carbs were rebuilt by a mechanic and the motor ran good. It was running fine and now all of a sudden I can start it and after warming it up it will run in gear moving for about two minutes and then dies. Then it’s hard to start but eventually I can get it to fire back up. During this whole time the primer bulb stays hard, like hard to pump. At first I thought I fixed it cause I saw that the gear shifter arm inside the motor was pinching the fuel line against the carb when it was in gear, so I re-routed it. Still the problem persists. I emptied out the fuel filter, no debre and no water. Also the fuel is brand new so can’t be that. I’m lost and don’t know what else to check.
Is it normal for the fuel primer bulb to stay really firm?

 

[tacx]

Make sure your fuel tank is getting air. If it isent venting the engine will run for awhile then quit when the tank gets a vacuum in it. That being said, when that happens the fuel bulb usually collapses? But not always.

 

[Newtlaw88]

The vent is open. I even lossen the main fill cap some to make sure it’s gettting enough air.

 

[Newtlaw88]

Well I checked the spark plugs. They appear to be new. But don’t seem dirty at all. Could the motor be getting too much fuel. There is some fuel in the water around the motor.

 

[jimmbo]

Fuel in the water, might mean gas is going thru the engine without being burnt, which is sort of normal even when the engine is running normal, or the carbs are flooding, or the carbs lose fuel when tilted and that fuel ends up in the water.

Running then quitting... Try a different tank and also a different fuel line, separately and in combo

 

[Newtlaw88]

Ok will do. Defiantly seems likes it’s getting too much fuel

 

[Newtlaw88]

Still the same problem with a new tank and fuel hose

 

[Newtlaw88]

Help??????????

 

[444]

Float level too high could cause the engine to tend to want to flood, although that wouldn't make much sense for a new development. Try trimming the engine down all the way to see if that changes anything. A ruptured fuel pump diaphragm can cause the engine to draw fuel in through the pump, eventually flooding you out. If it dies and you think it's flooded, try pulling your spark plugs, cranking it over to blow out the excess fuel, dry off the spark plugs and restart. It should restart without too much trouble.

It could be dying because of lack of fuel. An air leak anywhere will do it. Check all fuel line connections are good and clamped with gear clamps, could be an air leak at the fuel pump or carbs. I would change the fuel filters just to make sure they are no restriction.

 

[Newtlaw88]

I’ll check that but I don’t think this motor has a fuel pump

 

[jimmbo]

I’ll check that but I don’t think this motor has a fuel pump

So how would the gas get from the tank to the carb?

 

[Newtlaw88]

So how would the gas get from the tank to the carb?

From what I can see there is no separate fuel pump on this motor, maybe built into the carbs. Not all engines that are carbureted have fuel pumps.

 

[jimmbo]

Serial Number?

The only way it would not have a fuel pump is either gravity feed from a cowl fuel tank or a pressure feed system, and mercury hasn't used that since the 1950s. They did make a 45 in the mid 50s, hmm... Na, you said yours has power trim. It has a fuel pump

 

[Newtlaw88]

Serial Number?

The only way it would not have a fuel pump is either gravity feed from a cowl fuel tank or a pressure feed system, and mercury hasn't used that since the 1950s. They did make a 45 in the mid 50s, hmm... Na, you said yours has power trim. It has a fuel pump

Ok you win lol
where can I find the serial number?

 

[jimmbo]

Try looking all over the transom bracket, tilt and swivel housings. There is supposed to be a welsh plug on the engine block that also has the Serial Number on it

 

[Newtlaw88]

Try looking all over the transom bracket, tilt and swivel housings. There is supposed to be a welsh plug on the engine block that also has the Serial Number on it

So I had a mechanic look at it today and he said it’s an 1985. He tested sparks and everything was good. But he said it sounds like it’s only running on three cylinders. He said the carbs are getting fuel but seems like something is wrong with the carbs. They were just rebuilt three months ago and it was running fine. Now this problem suddenly. Any recommendations
also he recommended replacing the motor because he said it’s very unreliable and they always break and that the wiring always goes to **** on them. Any comments?

 

[Newtlaw88]

Bump!!!!

 

[racerone]

Brown / copper decals would be an 85 model.----Why would you say there are no fuel pumps on this motor ??-----Compression numbers are ?----Checked water pump impeller, yes or no ?----Checked for blockage in exhaust tuner ?----They are a sweet , reliable motor if in good condition.----What other trouble shooting has been done ?

 

[Newtlaw88]

It’s the blue and black decals. The mechanic said it’s getting plenty of fuel. And he did a spark test. All cylinders are getting spark. It pisses water fine. How would the impeller effect the motor running?also how do I check the exhaust tuner?

Brown / copper decals would be an 85 model.----Why would you say there are no fuel pumps on this motor ??-----Compression numbers are ?----Checked water pump impeller, yes or no ?----Checked for blockage in exhaust tuner ?----They are a sweet , reliable motor if in good condition.----What other trouble shooting has been done ?

 

[jimmbo]

As Racer said an 85 would have a series of Brown strips on the cowl. Blue was used from 72 - 83. That said,it might not be the correct cowl. What is the Serial #?
If all cylinders are getting spark, perhaps at least one of the plugs is not letting the spark get to the gas. Since each carb is shared by two cylinders, it is difficult to blame the carb for a dead cylinder. Compression numbers?
You might have a bad crankshaft seal, which would reduce the crankcase compression/vacuum