sputtering motor, water in fuel?

[jpcody66]

I have a 17' Four Winns with a 120 Mercruiser I/O. When I run the water muffs on it in the yard it runs fine but after I put the boat in the water it didn't want to run. It idles but would bog down after trying to accelerate then sounded like it was running on only three cylinders then back to four. I checked the plugs and they are dry. Could it just be water in the fuel or could there be something more going on?

 

[vipzach]

Re: sputtering motor, water in fuel?

It could be water in the fuel. When was the last time you did a full tune-up? carb rebuild, timing, cap and rotor (points), new filters, oil change, all of that knida stuff?<br />BTW welcome to iboats!

 

[jpcody66]

Re: sputtering motor, water in fuel?

Thank you,<br />I replaced the points (gap .021) and condensor, spark plugs, replaced the coil, changed the oil and drained the fuel and replaced with fresh and a bottle of dry gas. I didn't run through a full tune up though. Nor did I replace the dist. cap or plug wires. Do you recommend the cap and wires? I will have someone time it since I don't know how. I ran it yesterday on muffs and it seemed to get a little warm. First time I had seen it do that.

 

[Haut Medoc]

Re: sputtering motor, water in fuel?

What about changing the water separator, did you do that? Yes it sound like water in your fuel....JK

 

[jpcody66]

Re: sputtering motor, water in fuel?

I didn't replace the water separater filter. How do they wear out? I'll replace it as well.

 

[rbezdon]

Re: sputtering motor, water in fuel?

They were out in the same sense that an oil filter wears out and needs to be replaced. Dirt, water and contaninants can collect in it causeing poor fuel flow.

 

[jpcody66]

Re: sputtering motor, water in fuel?

Since the boat is now out of the water and I have fresh fuel and dry gas in the tank can I bypass the water separator for now? I have the impression that the motor is starving for fuel. I have a manual squeeze pump on the line and if I keep squeezing while the motor is running it will idle fine but a few minutes after I stop it starts to lose RPM's then slowly dies.

 

[rbezdon]

Re: sputtering motor, water in fuel?

sounds like its time to clean inspect and repair the fuel delivery system. Measure fuel pump pressure, clean and replace seperator, inline filter pick up tube and screen and antisiphon valve. Yes you can bypass it but you run the risk of the problem being crud in the tank having clogged up the filter now being passed to the carb and then you have to rebuild it too.<br /><br />I would just fix the problem with the fuel flow. Also, what the heeck is a squeeze pump doing on an I/O. That shouldnt be there and may be a part of the problem.

 

[jpcody66]

Re: sputtering motor, water in fuel?

Thanks Ron, I'll take your advice and get everything cleaned up. I had bought the boat just this year and was a little surprised to see the squeeze pump on it as well. I placed a small see through fuel filter on the hose from the tank and haven't seen any crud yet but that doesn't mean it's not there. I'll remove the squeeze pump too. The fuel pump should be providing that function.

 

[jpcody66]

Re: sputtering motor, water in fuel?

I took the squeeze pump off and routed a new line. I checked the fuel pump filter and it was bent 45 degrees. I replaced it and the water sep filter and vent tube and it ran great but started overheating. I dropped the bottom section of the drive and found impeller shrapnel in the intake. Replaced the impeller and the engine runs great and keep a steady 130 degrees or so. The exhaust manifold even became cooler than what it was sitting in the sun. Thanks everyone for all the help!

 

[vipzach]

Re: sputtering motor, water in fuel?

Glad you got jcody, those impellar have to be replaced every couple of years on an alpha drive. Never run them dry, don't even turn the motor over without water going to it. Thanks for the update, we like hearing something good!!!!

 

[jpcody66]

Re: sputtering motor, water in fuel?

Ok, the motor runs cool and idles smooth but now when I bump the gas a little forward it sputters and backfires. Could I still have water in the fuel even after adding dry gas or am I looking at a carburetor rebuild? All filters have been changed on the fuel lines, the flame arrestor has been cleaned, the timing seems ok. I read in the Clymer manual that I should replace the accelerator pump because the neoprene seal expands on the older models. My carb# is MCM-120 / 1351-6065A1. Could this be the culprit?