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Old 26-08-2010, 08:21   #1
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Finicky Old Two-Stroke !

I have an approx. 11 year old Tohatsu 5 HP 2 stroke, that wasn't started for about a year. I dumped the old fuel and refilled the tank with just mix. Took a while, but finally got it started, blasted a few donuts around my and my friends boats, and it seemed to run ok on 2 short trips.

Since then, I added a little Ethanol treatment to the tank (since it is an old engine, I figured this was kind of a must) and put in a new spark plug. Now it seems to start much easier (last time on the first try), but runs kind of funky. Really high RPM. If I let the throttle down too much it stalls out. So I seem to have to put it in gear with a little throttle, so I kind of blast off. Also once underway, even at full throttle, it has no umpf. Not like those first few trips.

Any ideas?
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Old 26-08-2010, 09:55   #2
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Any time a small o/b won't idle well it is time to clean the carb. It's not a tough job. Unbolt it and clean out all the small passages you can find with carb cleaner.
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Old 26-08-2010, 10:43   #3
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As an owner of an old 2 stroke...

Please let me add my 2 cents. After rebuilding and cleaning my carb, it still ran funky. A non-sailor suggested I use high test fuel in it with my 2 stroke oil of course. Damn, didn't it seem to run better and idle smoother. Something to do with the lesser amount of ethanol in the more expensive fuel. I suppose the ethanol evaporates or something....I have no clue, it just works for me.

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Old 26-08-2010, 12:08   #4
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Newish 2 stroke but still a pain in the neck. Learned that ethanol does not like the oil in the mix and viceversa, so the ethanol-oil combo turns into muck and obstructs fuel flow in/out the carburator. The carb needs to be opened and cleaned properly, especially the tiny hole that allows air into the mix. The lack of air is equal to lack of fuel when it comes to no umpf or stalling.

What seems to work for us is to always disconnect the fuel hose and let the engine run until it empties the carb every time you stop the engine for the night (meaning you don't have to do that if you are going to restart it in a couple of hours).

And yes, went through that while moored at the 79th Street Marine Basin in Manhattan and were stuck on the boat for two days and emailing everybody for advice until finally could start the darn dinghy motor. To see New York and not be able to go to shore is very upsetting, I tell ya'.
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Old 26-08-2010, 20:42   #5
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Grunster,where are you?

We used to have to go through our Tohatsu 9.9 carb about once a month in Mexico due to the crap in the gas. We had an inline filter, but brownish gunk still got through...
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Old 26-08-2010, 23:27   #6
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I'm in NJ.

Got the cleaner. Guess I'll start with the carb, once I get back on the hook, and out of this expensive marina.
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Old 30-08-2010, 12:22   #7
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rpm went even higher last night, and then it stalled. Not sure about the small hole you're talking about, but unbolted the carb, and sprayed the **** out of the whole thing with cleaner, inside and out.

Ran the engine a few times after that. Starts pretty easily, but extremely high rpm, and it barely even moves the boat at all now.

I do see water coming out and prop is spinning. Prop also appears to be in good shape.

Help! Now what?

I'm about ready to send this thing to thee drink and pick up a new 4 stroke.
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Old 30-08-2010, 12:27   #8
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I think you are getting fuel starvation. If it will run at high rpm but won't idle it sounds like when you disconnect the fuel line and let the carb run the fuel dry.

I'd get a carb rebuild kit and take the whole thing apart, put in new gaskets, check the float, and make certain the jets and all passages are clean. If you've ever used ethanol fuel in it you are doubly certain of having a lot of yellowish gunky stuff in there.

kind regards,
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Old 30-08-2010, 16:14   #9
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I'd get a carb rebuild kit and take the whole thing apart, put in new gaskets, check the float, and make certain the jets and all passages are clean. If you've ever used ethanol fuel in it you are doubly certain of having a lot of yellowish gunky stuff in there.

kind regards,
If? As if you can even find non ethanol fuel these days. There was some yellow gunk on/in it. Should I try disconnecting the fuel line from the carb first, and spay a bunch of cleaner in there? I didn't do that the first time.

How do you check the float?
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Old 30-08-2010, 16:38   #10
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I guess we're lucky here. A gas station within 15 miles has non-ethanol gas so I make a trip up there once in awhile to fill up a five gallon can.

Once you've removed the carb and the fuel lines you can use carb cleaner and compressed air to blow out the jets. You've got some good carb cleaner so that'll help get rid of most the ethanol junk. The float might be making the little needle stick in the closed position just enough to starve the carb of fuel. Just make certain it does float and also opens when the engine uses up the fuel in the chamber. Since you had some yellow gunk in there then definitely once you've cleaned everything up nicely and put it back together then your problem will go away. Check for any air leaks in your fuel to the tank lines. If there is a fuel filter anywhere make certain its clean too.

Good luck. I hope you can get it to work properly again.

regards,
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Old 31-08-2010, 07:45   #11
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Now I have the opposite problem. Took it apart again. This time I disconnected the fuel line and removed the float. Sprayed the **** out of everything with cleaner. Now it's idling ridiculously low, even at full throttle...and still won't move the boat.

Is it just time? This thing is 11+ years old. And considering how much these older engines love ethanol...and the almost non existent availability of non ethanol fuel, at least in the US. Maybe time for a shiny new 4 stroke?

Or can I try something else. Seems the more I clean it the worse it gets.
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Old 31-08-2010, 08:06   #12
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Update: prop doesn't seem to be spinning now.
Also no longer pumping water...as if it needs it at the insanely low rpm it's running at.
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Old 31-08-2010, 08:07   #13
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Quote:
Originally Posted by grunzster View Post
Now I have the opposite problem. Took it apart again. This time I disconnected the fuel line and removed the float. Sprayed the **** out of everything with cleaner. Now it's idling ridiculously low, even at full throttle...and still won't move the boat.

Is it just time? This thing is 11+ years old. And considering how much these older engines love ethanol...and the almost non existent availability of non ethanol fuel, at least in the US. Maybe time for a shiny new 4 stroke?

Or can I try something else. Seems the more I clean it the worse it gets.
My experience is that 4 strokes are much more picky about fuel quality, so if you are concerned about fuel quality, I would stick with 2 stroke. Not sure I ever have seen data to support the fact that ethanol enriched fuel has issues with oil, I would love to see that data if it exists.

I did purchase a product called a Mr Funnel for 25 bucks. I use it everywhere I go, and have had luck with keeping the fuel in decent shape. Also I will at least once a month run any gas not used in tanks thru it to get rid of any water created by condensation.

Another product I swear by is yamaha ringfree additive, pricy, but seems to keep my little engines running top notch.

Note my main propulsion for the boat is an outboard, so I am rather particular about keeping them running, but since they are mechanical, I never trust that they will work, and make decision accordingly. :-)

Cheers
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Old 31-08-2010, 08:07   #14
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Wait, wait wait....

The shaft is connected to the prop - yes?

If the engine is running at "high" rpm and the boat is not moving then number 1 suspect is the prop shear pin if installed or whatever keys the prop to the shaft.

Idling and rough running are engine issues. High rpm and the boat not moving is a prop problem.

I suspect the "crash" engagement (high rpm and drop into gear) may have sheared the pin.
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Old 31-08-2010, 08:10   #15
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Wait, wait wait....

I suspect the "crash" engagement (high rpm and drop into gear) may have sheared the pin.
Or possibly the plastic/rubber hub inside. One of the reason I prefer worldspec engines is that the props do not have the breakaway hubs. I use brass pins that break earlier than stainless, and make a point to be as situationally aware of prop vs bottom/object as possible.

Cheers,
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