Hesitation

[digginfool]

Was running my boat last evening and it began to act like it was running out of fuel. I switched fuel tank selector thinking perhaps I had run the front tank dry but the problem continued. This morning checked for water in the float bowl and water separator but did not find any. Carb was recently rebuilt so I don't think that's the problem. SV 540 with Pacemaker. Any ideas? Perhaps the mechanical fuel pump? I don't use a lift pump and I've never had any problems in the past on this boat or the other boat I had this engine on with fuel feed issues but I guess there's always a first time.

 

[Slidin Gator]

Diggin,

As I'm sure you know, there are lots of reasons other than fuel that she may stumble, but fuel is always high on my list... We have had issues with the SV 540 doing just as you describe, the solution was to change the fuel filter (vs check it). We specifically run a very large NAPA 3418 water separating fuel filter between the tank and mechanical to minimize the occurrence. I have pulled them off and dumped them out where everything looked clean with no water and had the same issue repeat. Replace the filter and no issues. One time we could not get the engine to crank after a shut down, even with the electric lift pump running, swapped fuel filter and she lit right off.

Between a float that might be a bit sticky or on the heavy side of adjustment and a bit of drag on the filter side, some rigs can be sensitive to pressure drop. Change the filter and see how she runs.

 

[digginfool]

I'm running a Racor 3232 filter as I like to go on the larger size as well. It's not even been a year since I changed it but I'll give it a shot. Hopefully, that's it.

 

[SWAMPHUNTER45]

Would it run at full power for a bit and then go flat or did it have a lower power issue off the initial romp of the pedal?

 

[digginfool]

It was mostly while running mid-range and it would stumble as I added throttle to control the boat around a corner (deck-over and very free). That's why I initially thought that I was running out of fuel, thinking that the fuel was sloshing from one side to the other while navigating the turns on the trail I was running and the engine was intermittently sucking air through the fuel line. But, as I stated above, after switching to the rear tank, which I knew was full, it didn't get any better. I didn't want to experiment too much since it was already dark on a Sunday night and I wanted to make sure I made it back to the landing so I wouldn't have to inconvenience any of my buddies.

 

[Slidin Gator]

I didn't want to experiment too much since it was already dark on a Sunday night and I wanted to make sure I made it back to the landing so I wouldn't have to inconvenience any of my buddies.

I woulda stopped to experiment (just when the Skeeters come out). It's a good way to weed through the list of buddies you really want to burn AV Gas on. :lol:

 

[DukHntr239]

Would it run at full power for a bit and then go flat or did it have a lower power issue off the initial romp of the pedal?

My o540 has a lower power issues off the initial romp of the pedal like you’re saying here. I’ll give the pedal a good push and it will kind of do a little hiccup, or hesitate and then be perfectly fine through the throttle. Is that pretty normal?

 

[Slidin Gator]

I’ll give the pedal a good push and it will kind of do a little hiccup, or hesitate and then be perfectly fine through the throttle. Is that pretty normal?

Nope, try several quick half throttle punches before a full throttle romp. If the half shots help, time for a new accelerator pump.

 

[DukHntr239]

I’ll give the pedal a good push and it will kind of do a little hiccup, or hesitate and then be perfectly fine through the throttle. Is that pretty normal?

Nope, try several quick half throttle punches before a full throttle romp. If the half shots help, time for a new accelerator pump.

It’s actually the half throttle pushes when it does it. Mainly like when I’m stopped on dry ground, and I give it a good push to get going it will do a little hiccup. We’re talking maybe like 1/4 throttle to half throttle is about when it does it.

 

[Slidin Gator]

A rich adjustment might help, is this a MA4-5 carb? There should be a big thumb knob dead middle looking at the carb from the stern, screw with that.

 

[DukHntr239]

A rich adjustment might help, is this a MA4-5 carb? There should be a big thumb knob dead middle looking at the carb from the stern, screw with that.

Yes sir, it is an Ma4-5 carb. Thank you for your help Mr. Gator. I will try messing around with that.

Since we’re on the carb subject. I have a spare good working Ma6 I got from a friend since he switched to injection. What is the difference? And would that carb benefit my angle valve upstack o540 better than the Ma4-5?

 

[Slidin Gator]

Since we’re on the carb subject. I have a spare good working Ma6 I got from a friend since he switched to injection. What is the difference? And would that carb benefit my angle valve upstack o540 better than the Ma4-5?

The 6AA has automatic altitude compensation, the 4-5 does not. I have tried both on a SV O-540 and did not find any noticeable difference.

 

[SWAMPHUNTER45]

Sounds like your pointed in the right direction.

 

[digginfool]

Well, fresh fuel filter didn't make a difference. In fact, barely made it back to the landing this morning. The way it was popping and sputtering makes me think it may very well be an ignition issue. It was barely running above idle by the time I made it to the trailer. Couldn't run it up enough to even get it on; had to hook up the strap and crank it up onto the trailer. Recently had a Pacemaker installed so.... If it's the Pacemaker, pretty sure I'll be looking to go back to mags. Guess I'll be heading to FXE tomorrow.