starts, putts, dies

[hibbert6]

Need help. Last week I uncovered my boat (merc 650) took it out for a half hour and it ran beautifully. On Sunday, I towed it 200 miles to an extended- family vacation on a lake. Launched, she fired right up. I putt-putted out past the bouys and opened her up. After about a minute she began to sputter. Not like running out of gas - I was able to play with the throttle to keep her running. As the weeds in this lake can get thick, I figured that might be the problem. So I put it gently into reverse for a few seconds then forward again - it seemed to help a little. Putted back to the dock.

Next day I cleaned a few weeds off the prop, then my wife took the boat out. Putted fine to the bouys, then opened it up. After 30 seconds or so, she couldn't keep it running. Ran out the battery trying to restart the motor. Had to be towed in.

Today I pulled her out, pulled the cover and checked the plugs. A little worn, a bit oily, maybe, but fine. Cleaned them with a rag, and put 'em back in. Lacking a charger, I hooked up the pull cord, turned the key to "on" and yanked. She started right up. As I had no muffs, either, I played with the throttle for about 10 seconds - she sounded great - and shut her down.

But I know that if I take the boat back out, the same problem will probably occur. I checked the choke - the plates are open. The fuel mix is right, I'm pretty sure - besides, if it were too "oily" it would run poorly from the get-go, right? Any ideas? My family is not happy!

Dave

 

[bustermin]

Re: starts, putts, dies

You said you checked the plugs, did you check the fuel filters? dont forget the pick up line, sometimes it can become clogged.

 

[T.]

Re: starts, putts, dies

I feel your pain. My 125hp did the exact same thing a few weeks ago. I was thinking fuel pump, dirty carbs, etc. It turned out to be nothing more than a spark plug that went bad while on the water. It did not look bad, but was. I hope yours is a simple fix too.

Todd

 

[hibbert6]

Re: starts, putts, dies

You said you checked the plugs, did you check the fuel filters? dont forget the pick up line, sometimes it can become clogged.

I feel your pain. My 125hp did the exact same thing a few weeks ago. I was thinking fuel pump, dirty carbs, etc. It turned out to be nothing more than a spark plug that went bad while on the water. It did not look bad, but was. I hope yours is a simple fix too.

Thanks, guys. The fuel filter is transparent and looks good, and I'm having the same problem with both gas tanks, so I don't think BOTH pickup lines would clog at the same time. And, the boat is running longer than when, for example, I forget to connect the gas line. I'll replace plugs tomorrow - it's probably time anyway.

A friend said "2 strokes - when there's not enough oil, they flood." Does that sound like it might be my problem?

 

[86RajunCajun]

Re: starts, putts, dies

When there is not enough oil, they tend to implode!

Starving a 2 stroke of oil for even a few seconds can cause serious internal damage.

First off make sure your fuel/oil mix is 50:1. You can get a bottle from wally world for 4$ that will enable you to mix the oil perfectly. I suggest you get one.

Second, this loss of power or sputtering your talking about could be caused by a number of things.

Lets start with a compression and spark check on all cyl's.

Make sure all the spark plug wires are secure and the rubber insulation is not dry rotted or cracked as this will cause the spark to escape the wire and arc to the block etc.

If compression and spark pan out to be good, then we will go into the fuel system.

First verify that the choke is not sticking open and flooding the engine out.

If the choke is operating correctly, then lets take apart the fuel pump assembly and check for pin holes in the diaphragm, clean the internal mesh filter and give the pump a good look over for anything out of the norm <dry rot, cracks in gaskets, corrosion etc.

After you make sure the fuel pump is in top shape follow the fuel line/system from the pump to each carb and ensure their are no holes or otherwise air leaks in the system.

If all the lines are solid and sealed, lets move on to the pump to tank lines. Male sure once again that they are all solid and sealed and no leaks.

Pay close attention to the primer bulb for leaks as i have sen them get pin holes from dry rot and cause this type of condition. For 7$ at wally world a new primer bulb and line are a solid investment.

If all fuel lines and the fuel pump are in good shape we can rule out the fuel system components and start looking at either spark, timing, or internal engine items.

Some of these which would cause your condition would be...

Clogged carbs causing a lack of fuel, or stuck open needles causing a flooding condition. Bad floats, or seats or leaking carb gaskets.

If the carbs check out and you clean them good, you can rule them out.

After checking the carbs over, you can move onto the rest.

First after checking the fuel system over, we will move on to static timing the engine.

Remove all the plugs and ground them to the block. Hook up your timing light on the #1 plug wire and a power + good engine ground and dis connect the throttle cable from the throttle arm linkage to allow for manual control over max throttle.

With a helper cranking the engine, time the engine at base throttle and adjust the max spark advance screw within spec for your engine.

After the base timing is set, have your helper crank the engine and push the throttle arm to WOT throttle and record the timing measurement. Adjust if needed to the max timing value for your engine.

The timing values can be found in the shop manual for your engine assuming you have one <which you should or your just plain wrong!>

After the timing has been checked and set correctly if needed, if the problem still persists, we can move on into advanced territory and start looking at the reed block and the reeds.

Damaged reeds can also cause the problem your having.

So i think we have given you enough to start with, so break out the shop manual and start going over each system in detail and make sure things are strait, and we will go from there.

GL
RC

 

[coolguy147]

Re: starts, putts, dies

i think u should replace the impeller y ur at it. especially since u played with the throttle. 10secs is really long for an impeller never run a motor without water. just to be on the safe side i would replace it

 

[hibbert6]

Re: starts, putts, dies

RagunCajun,

Thanks! I think I'l try your entire procedure when I get home from vacation. It's about 90* most of the day here at the lake, and shade is hard to come by, so I'm trying to address the most likely/easiest -to-repair causes of the problem first. Or, rather, only. I'd rather spend my vacation enjoying my family around the pool than working on the boat the entire time. And my wife definitely approves of that plan, too, though the kids would rather I got the boat running!

I've already recently replaced the fuel line, bulb and filter. I have the mixing bottle and used it; I have reviewed my mixing ratio and know that it's accurate at 50:1. Therefore, I assume mixture, air in the line, etc. can be eliminated as the culprit. (And, yes, I do have a manual and know how to use it. )

Everything makes sense, except that, as I mentioned, everything works fine for about 5 minutes, then sputters and dies. Wouldn't that eliminate plug wire problems, compression problems, etc? The choke, however, might be it. However, I don't recall having to use the choke to start the engine. But it could be stuck, anyway, I suppose.

Isn't the choke the circular plates over the carb throats? They were wide open when I tested it yesterday with the cover off.

Taking apart the fuel pump, replacing defective parts, etc. while on vacation begins to sound like real work. Still, I'm thinking that this problem is something pretty simple, as the engine ran perfectly last week.

So how about the choke? Am I looking at the right gizmo?

Dave

 

[86RajunCajun]

Re: starts, putts, dies

Well, in my experience, with these marine electronics and ignition, sometimes they will work till the circuit heats up, then you have a problem.


The choke should NOT be wide open EVER unless you are actually choking the engine. If the choke stays open, it will flood the engine out and cause exactly the problems you are having because the flooding fuel will douse the spark.

Im not 100% sure on the location or appearance of the choke on your outboard, but you manual should show you a picture of it in the fuel system section.

I would first check that choke and see if you can get it closed before you do anything else. Then if the choke is sorted, move on to the electrical troubleshooting. Iv seen coils that would deliver spark fine till they were in use for a few and they got hot and shorted out causing a cylinder to drop.

Iv also seen this happen on my own outboard with the trigger causing cyls to drop out.

So check that choke and make sure it is operational, and if so, youll need to break out a volt meter and get a DVA adapter to start testing the ignition components. First thing to do tho is to get it hot, and get it acting crazy and test spark on all cyl's.

The running for 5 mins condition could be the engine running off what fuel is in the bowls, and then onmce that is depleted, the fuel pump will be working to refill the bowls. If the fuel pump has a pin hole in the diaphragm, then it will not be able to supply the fuel pressure needed to keep the bowls topped off and cause a lean condition. Lean or rich could cause a sputter and caugh and even misfires.

GL
RC

 

[hibbert6]

Re: starts, putts, dies

Cajun, and All who've contributed -

Thanks for your help. I've tried a few of the fixes, so I'm about to go back out on the lake. Wifey is not thrilled by the idea of a mid-afternoon 95* launching, but I agreed to suffer the consequences if I'm stranded on the lake. I'll take lots of drinking water and my cell phone. And maybe beer to compensate whoever tows me back in...

Dave

 

[hibbert6]

Re: starts, putts, dies

Well, I took it out and it ran great! ( Well, as long as I was out of the weeds. Yuck.) I have no idea what was causing the problem.

Thank you all for your help. I'll try Cajun's steps when I get home.

Dave