Can you rejet a carb, could this be my problem ???

[jyenney]

I've written a couple of times and done a lot of things to try to cure this problem. My 1999 merc 75 hp runs great and doesn't cut out at all from 0 to 4200 RPM's. When I give it full throttle and get on it, the motor starts to cut out every 5 to 10 seconds at 5000 to 5100 rpm's. I have also noticed I have a oil/gas (thick) mixture that leaves a heavy residue on the inside of my motor on my intake, and also blows the mixture on the inside of my transom 1 foot inside my boat.

A couple of weeks ago it was only cutting out at WOT every 1 to 2 minutes.

My question is, the boat is from North Dakota, guessing 2000 Feet in elevation. Where I live the elevation is at 4000 to 4500 hundred feet in elevation. Do or can you jet your carbs ?? and any idea why I would have this heavy residue. I've changed my fittings and cant find a leak anywhere.

 

[j_martin]

Re: Can you rejet a carb, could this be my problem ???

I've written a couple of times and done a lot of things to try to cure this problem. My 1999 merc 75 hp runs great and doesn't cut out at all from 0 to 4200 RPM's. When I give it full throttle and get on it, the motor starts to cut out every 5 to 10 seconds at 5000 to 5100 rpm's. I have also noticed I have a oil/gas (thick) mixture that leaves a heavy residue on the inside of my motor on my intake, and also blows the mixture on the inside of my transom 1 foot inside my boat.

A couple of weeks ago it was only cutting out at WOT every 1 to 2 minutes.

My question is, the boat is from North Dakota, guessing 2000 Feet in elevation. Where I live the elevation is at 4000 to 4500 hundred feet in elevation. Do or can you jet your carbs ?? and any idea why I would have this heavy residue. I've changed my fittings and cant find a leak anywhere.

Yes and probably no.

At higher elevations, you change the carburetion to a leaner setting, as it isn't getting as much air. You are likely running rich.

Usually high speed cut outs are either ignition, or fuel delivery, as in fuel pump, tank venting, and such. You can do serious injury to your engine if you run it with a fuel delivery problem.

Everything you need to know is in the manufacturer's maintenance manual.

hope it helps
John

 

[Camo Joe]

Re: Can you rejet a carb, could this be my problem ???

Clean the fuel lines...........Clean the carbs..........check the carb float levels, seats, and needle valves..............could be restricting the flow........or sticking..............Check the fuel pump for operation and restriction...........

Check the ignition wires for leaks upon movement......(a bad spot)