Need help diagnosing Honda 50 problem

[mike]

As mentioned in my post a few days ago, we encountered engine trouble on our recent trip. I will summarize here again, and go into some additional details (sorry, this is sorta long)...

Engine ran great for about 2 hours, cruising at about 5,000rpm. Engine started to lose power, and I assumed tank #1 (6gal DuraTank) was empty, which it appeared to be. Switched to tank #2 (6gal DuraTank), and we continued on our way. A few minutes after that, the engine began exhibiting the problem that would plague us for the rest of the shortened trip.

We'd be cruising along, engine sounding fine, then suddenly the engine would lose power, running very roughly with a dramatic drop in rpms. This would happen whether we were at high rpms or moderate rpms. Pulling the throttle back to idle would result in the motor dying. Pushing it forward did not produce any noticeable difference in power, aside from the more "throaty" sound of the carb's valves being opened wide. After a period of time, anywhere from a few seconds to a minute or two, it would jump back to full power and run fine. This cycle repeated over and over at random intervals.

I immediately suspected fuel contamination, since the problem seemed to coincide with switching to the 2nd tank. There did appear to be some debris in the tank, though I would have thought that this would have been caught by the canister-type filter/water separator that is installed. I drained the float bowls several times, and switched to a 3rd tank, but the problem continued. After anchoring overnight, hoping that whatever the trash was that I presumed was in the carb(s) would have settled to the bottom of the float bowl, I drained them once again, but after motoring for 10 minutes or so, the problem started happening again.

After sailing most of the way home, we employed the motor to get us through the bridges, and the problem worsened to the point where it was barely running at all.

Now, though I've thought all along that it was likely a fuel problem, however, I'm now having second thoughts about this. After sharing my woes with a slip neighbor, he suggested that it could be ignition related. Hearing this made me realize that the nature of this loss of power was not gradual (as in, taking a couple of seconds to go from normal power to running poorly), but rather very abrupt and sudden, like a "run crappy" switch had been flicked. Likewise, the regaining of power was similarly instantaneous.

Running the boat at the dock (in gear, 3,000rpms) for about 10 minutes (that's all I had time for yesterday), all was well, but it probably just needs to be run longer than that for the problem to show itself.

Any thoughts on this? Any ideas on what I should pursue first?

--Mike

[craiglaforce]

Have you ruled out the air leak at the top of the fuel tank? Don't forget, the engine will run fine for a couple minutes or so on the fuel left in the hose/ primer bulb / carbs and filters. Then, when it starves for gas it runs crappy. I ended up putting 5200 on the top of one of my fuel tank fittings that was leaking air. If you squeeze the primer does it feel hard immediately or can you feel air in there?

Granted, I've never seen your motor so it might indeed have a run crappy switch somewhere. Or maybe an electronic problem somewhere that shows up when it gets hot.

[Luke]

My Honda has had similar symptoms several times.

First time it was water in the gas.
I put several cans of Dry Gas into the fuel tanks. Problem solved.

Second time it was dirt in the carbs. Had the three carbs rebuilt. $600.00.

Third time it was a fuel line problem: replaced the inline bulb and fixed an air leak on the fuel fitting on top of the gas tank.

Luke
DreamChaser

[Mark Prouty]

Last summer I used a Nissan 4 stroke kicker motor that kept stalling in a similar manner. The fuel line at the hose clamp near the motor had a small leak in it. I removed the clamp, cut the line and reinstalled the clamp. The problem was fixed.

[mike]

Thanks for the responses so far... I will concentrate my efforts on the fuel system, but a nagging voice tells me it could very well be ignition related (as Craig said, something that only happens after the motor is hot).

The one thing that makes me think this is a quick test I did Sunday... I ran the motor, then kinked the fuel line to simulate a blockage. When the fuel in the float bowls ran out, there was not a dramatic drop in power... it took a couple of seconds to happen. On the other hand, when I did this, the motor sounded similar to what it did when the problem occurred out on the water.

I think my first step is to actually duplicate the problem at the dock, which will involve running it for a while under load. At that point, perhaps by examining each of the spark plugs, I can determine if perhaps the loss of power is related specifically to one cylinder (which is what it sounds like).

Oh, this is going to be fun!

--Mike

[Mark Prouty]

I'm just relating this to you because you might find it of interest. Its exceptionally unlikely it is your problem. Years ago, I had a Johnson 2 stroke outboard. It would run to the middle of the lake and then stop. This happened three or four times. Each time it would stop at about the same location. It turned-out that the alarm for an overheated motor was broken. Each time I ran it out to the middle of the lake it would overheat and seize up. The last time it happened was the end for this motor. It never started again. May it rest in peace.

[BobCardz]

I mentioned this earlier. Try replacing all of the Plugs and see if she idles any better. I had a Honda last year that would burn the bottom plug within an hours use. Then it was a 2000rpm trip back to the dock. I think it was a 2002 motor. Each year the standard idle seems to get worse... (must be EPA related)

Also if you have a voltage meter... check to see if the regulator is out of wack.

If the idle is still rough after all the plugs are changed... pull out the welders gloves and pull each wire from the plugs to see the difference in rpms. At least if it is fuel, you will know which carb is failng.

If you were closer to Pensacola I'd be happy to help.

[mike]

Mark,

I considered that, though the Honda 50, in addition to some sort of warning, is supposed to limit rpms when a low oil pressure or overheat situation is detected.

I made a little bit of progress this evening... I was able to reproduce the problem at the dock. With the boat tied up securely, I ran it in gear at about 4,000 rpms for a 20 - 30 minutes (during which time it sounded perfect), then abruptly ran horribly, then great, then horribly, etc.

Now that I know I can reproduce the problem in the slip (which I had no reason to believe I wouldn't be able to), I will begin the real troubleshooting this weekend. In the meantime, any additional comments / advice is welcome!

--Mike

[Russell]

make sure that the choke is not on in any way. On my 60hp yamaha I have an automatic and a manual choke. one day after replacing spark plugs I had a similar problem, I found out that I had accidently engaged the manual choke just partially when I had that type of problem. So rule out the easy stuff first.

[mike]

make sure that the choke is not on in any way. On my 60hp yamaha I have an automatic and a manual choke. one day after replacing spark plugs I had a similar problem, I found out that I had accidently engaged the manual choke just partially when I had that type of problem. So rule out the easy stuff first.

Actually, this was something I had considered... I have a mom-on switch on the pedestal for the choke, and it's been sticking in the on position lately. I thought that perhaps the switch had deteriorated to the point where it was shorting out by itself. So, I tried running the motor, and pushing the switch to engage the choke, but this resulted in the motor completely dying within a second or two.

But I will take a closer look at it (making sure it's not somehow partially engaging) just in case.

--Mike

[Frank C]

. . . . I made a little bit of progress this evening... I was able to reproduce the problem at the dock. With the boat tied up securely, I ran it in gear at about 4,000 rpms for a 20 - 30 minutes . . .

Mike,
I'm a little bit curious . . . did you just use the factory cleats to hold 4000 for 20 mins? And, how did the dock handle it? I can't imagine our marina operator smiling about that.

[mike]

I'm a little bit curious . . . did you just use the factory cleats to hold 4000 for 20 mins? And, how did the dock handle it? I can't imagine our marina operator smiling about that.

My aft cleats have been replaced with stainless steel ones, but I have not yet replaced the front ones. I adjusted my dock lines in such a way that the load was spread across the front and the aft cleats, and given the somewhat poor conditions the pilings are in (at least visually), I was indeed a little nervous about this, not to mention the possibility of the lines snapping. So, I sat there the whole time with my hand on the throttle (and trying to stay clear of the potential path of snapped dock lines). Everything seemed fine though... rather than just gunning the throttle, I eased it up slowly as the boat settled into position against the lines.

At this particular moment, I'm leaning heavily towards an ignition system component failure that is brought on by heat. If this theory is correct, I will be able to more easily reproduce the problem by employing a technique I read about elsewhere... use a blow dryer to warm up the suspected component to see if it induces the erratic behavior. If this is indeed the case, I won't have to run the boat at 4,000rpms during troubleshooting anymore.

--Mike

[Don B]

Mike,

It sounds like you are making more progress than I am with my Suzuki 50 4 cycle.

The only local dealer told me he is going to discontinue selling Suzuki motors and was no help.

The 2nd dealer I called it also the dealer who intalled the engine but is not local and he told me that he does not sell many of the small 50 HP engines but also told me that the fuel pump can be damaged very easily by water causing rust contamination.

He also suggested draining the fuel rail, checking the plugs, making sure of no vacumn leaks.

-Don B

[BobCardz]

Puts technology into perspective.

Makes them old 2 stroke where you mix oil and gas simple motors look more appealing.

[mike]

It sounds like you are making more progress than I am with my Suzuki 50 4 cycle.

Reading your threads regarding your engine woes, I can certainly empathize with your plight. It sure sounds like your particular problem is fuel system related. But then again, I initially was positive mine was fuel related too, while I am now fairly confident it's ignition.

Perhaps this was already mentioned in one of the other threads, but have you tried giving the primer bulb a squeeze when the engine starts to die at high rpms? I've read that this is a good way to test the fuel pump.

--Mike