Help with hydrolock-like symptoms

[sidechoke67]

I have had this happen to me several times now...

About once a month or so, I am out using my boat - usually pulling the kids on a tube. I turn my boat off, and it runs-on for maybe 3 seconds before stopping. When I try to start the boat the next time, I hear a clunk sound. I can turn the motor by hand during this time. Then, maybe 1/2 hour later or so, the boat turns over and starts fine. My boat runs-on maybe once a month or so...it isn't all the time. One time, it did this, and locked up just as I was about to get off the water anyway. This time, I used my trolling motor to get back to the launch, drove home, immediately pulled the plugs and turned the motor by hand looking for water coming out of the cylinders - there was none. I put the plugs back in, and the motor started right up.

Given that it happens after run-on, I am thinking some sort of "mild" hydro-lock, but my brother says that hydro-lock isn't a little thing, and waiting a 1/2 hour wouldn't solve the problem.

Any ideas or advice? It happened today, causing me to cut a trip short. By the time I towed my boat home, it started on the muffs at home just fine (without pulling the plugs).

Thanks!

 

[Maclin]

Re: Help with hydrolock-like symptoms

You need to fix the run-on problem because eventually it will lock up to where you will have to remove the spark plugs to get it to turn over.

Try letting the engine run for 30 seconds or so before turning it off. If it tries to run on turn it right back on and let it run a bit and try again. You can also turn it right ofter putting it back into gear. just be careful and aware of your tubers.

Your idle may be too high, or you may not have the proper heat range spark plugs installed. Fix a high idle, that will always want it to run on. Also, too hot of a spark plug range will act as a glow plug, so check that yours are to spec. Also make sure the idle mix is set to specs, too lean can cause conditions conducive to run-on.

 

[Maclin]

Re: Help with hydrolock-like symptoms

If not a hydrolock then the problem is probably electrical or electro-mechanical in nature, like a starter solenoid hanging up or an aging starter too hot to turn. If turning the engine by hand does not relieve the "clunk" sound then I think it is not hydrolock, although to be sure you need to pull the spark plugs while it is in the clunking mood and see if 1.) It cranks then and 2.) If it cranks if any water mist comes out of any cylinders. If it won't crank then turn by hand again to see if any water comes out.

 

[wellcraft19]

Re: Help with hydrolock-like symptoms

"run-on problem" can be fixed also with higher octane gas (yes, I know more $$$, but what would the "real" difference be during a summer) or like suggested above, different/correct plugs.

Mine is a bit of a high compression (for boats engines, AQ171C) set-up and it runs vastly better on premium gas. Not fun to fill up, but peanuts in the larger scope.

Since I had some dieseling issues just as I got the boat (likely not that "maintained" by previous owner), it took me a while to find the right combo of plugs. On top of that, I always let it idle to cool down for a while as well before "calling it quit".

 

[sidechoke67]

Re: Help with hydrolock-like symptoms

Great info - thanks guys!