Intermittent high-speed brief hesitations

[superbenk]

Took the boat out for the first time over the weekend & most everything worked perfectly!! One issue I noticed was that cruising at high RPM (~4000-4500RPM), things would run great most of the time, but occasionally there'd be a very slight hesitation for a second and then it'd be fine again. It was extremely subtle, but I could hear it and just barely feel it. It didn't register much change on the tach, though.

I'm thinking it might be something with timing or dwell adjustments or maybe fuel related (water, gunk, etc.) from sitting over the winter. I did use Stabil in the tank when I laid it up. Anything else I should check?

 

[superbenk]

Re: Intermittent high-speed brief hesitations

For those that didn't already know, this is an OMC 140/Stringer 400 outdrive in a 1980 Century 190.

 

[Philster]

Re: Intermittent high-speed brief hesitations

High demand for fuel at that RPM. I'd ditch the filter and replace.

I would suspect under heavy load (strong acceleration) that you'd find similar problems.

 

[superbenk]

Re: Intermittent high-speed brief hesitations

High demand for fuel at that RPM. I'd ditch the filter and replace.

I would suspect under heavy load (strong acceleration) that you'd find similar problems.

That was on my short-list as well. It's new as of last summer, but maybe sitting over the winter built up some junk in it. I think I'll get in the habit of replacing the filter every spring.

 

[180shabah]

Re: Intermittent high-speed brief hesitations

I think I'll get in the habit of replacing the filter every spring.

Good habit.

 

[superbenk]

Re: Intermittent high-speed brief hesitations

Replaced the fuel filter but still had the same hesitations today when we went out again. Seems like it occurs more when the engine heats up. We finally went out on the Delaware today and after a few miles at 4k RPM it started missing and hesitating so we dropped back to 3k RPM and it continued to do it. Almost thought it was going to stall a couple times, but we sputtered back to the ramp finally.

At this point I'm planning on replacing plugs, wires & testing/tuning timing again. Getting pretty frustrating not ever being able to trust my boat when we go out that it's going to get us home & it certainly doesn't seem capable of any kind of water sports at this point.

(Guess who's ready for a new boat? )

 

[toolsinbox]

Re: Intermittent high-speed brief hesitations

I would do a full tune up with attention paid to the plug wires, cap and rotor. You could have wires that have leakage to engine or to themselves. Good idea to check all conections and test coil.

Just a few other ideas for you.

 

[superbenk]

Re: Intermittent high-speed brief hesitations

I would do a full tune up with attention paid to the plug wires, cap and rotor. You could have wires that have leakage to engine or to themselves. Good idea to check all conections and test coil.

Just a few other ideas for you.

I did the cap, rotor, points last year as well as rebuilt the carb & really didn't much use on it since. I put automotive plugs in last year as well, but just ordered new marine plugs, wires & a coil.

Like I said, I'll replace those items I just bought & test/tune the timing & dwell again.

 

[bomar76]

Re: Intermittent high-speed brief hesitations

Sounds much more like garbage fuel and carb is full of trash.

 

[rjwoodrome]

Re: Intermittent high-speed brief hesitations

Mine this spring was doing the same. started to occur more frequently. finally found the wires going to the carb, the purple one had started to become frayed at the electrical connector. repaired problem solved. unfortunatly it had to fail compleatly before I was able to find it... drifted around for about 45 min. the only tools available were the crappiest home owner pliers that live in the boat Shame on me, the owner of an Electric and Heating Company.. No tools. that changed immediately. Spare basic hand tools in a water proof container. if the boat sinks the tools can be saved

 

[verado7]

Re: Intermittent high-speed brief hesitations

plug wires or ignition pack

 

[bomar76]

Re: Intermittent high-speed brief hesitations

ignition pack

Is that near the Kneudson Valve on a 4 cylinder I/O engine?