25hp hunts after idle

2

234rick

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1989 25hp evinrude tracker on 16' bass tracker panfish. Compression is 70 psi on both cylinders. It idles fine & runs wide open fine, I estimate it runs 20 to 25 mph wide open. I just got the boat & took it out yesterday, I ran it for 25 minutes wide open it ran fine. I let it idle for a few minutes & when I opened it up it started hunting BAD. The only way I could get it to run was to move back & forth from forward to reverse, & after playing with it a little it would take off in reverse & then it would run fine. I repeated this several times, it only takes about 30 seconds of idling to cause this. When it takes off its like something clicks because it runs perfect, no stumbling or hesitation it just goes great. Any ideas ? Thanks Rick
 
Cofe

Cofe

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Re: 25hp hunts after idle

Are you running fresh fuel, or last years fuel?
Could have some condensation built up in the fuel tank.
 
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234rick

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Re: 25hp hunts after idle

Gas is new this week premium gas & johnson oil mixed 50:1. I drained the old gas & thorouthly cleaned the tank. What gets me is I have to put it in reverse to get it to run right & when it does run ok its immediatly running right. Its like something switchs when it idles & then release or switchs or pops & it starts running wide open again.
 
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234rick

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Re: 25hp hunts after idle

I know the compression is low I hope it will improve. But the motor runs good & moves the boat along pretty good. I'm looking for another tester to check the compression.
 
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234rick

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Re: 25hp hunts after idle

I would have thought someone would have an answer for this by now. Does this motor have a slow mode switch ? Maybe it is getting to hot when it idles & it cools off when its hunting & switchs back.
 
Mas

Mas

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Re: 25hp hunts after idle

Your low psi may be your gauge...but you may want to do a decarb using some seafoam to maybe loosen up the rings if they're all coked up.

Mas
 
J

jonesg

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Re: 25hp hunts after idle

Ditto on the decarb and look for a compression leak on the cyl head.

Check the throttle plates both fully close, and both should be 90 deg horiz at WOT. Otherwise link and sync is in order.
 
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234rick

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Re: 25hp hunts after idle

Ok I got another tester it tested the same 70 in both cly.. I ordered a factory manual & did a link & sync the throttle plate was going past horizontal quite a bit. I adjusted that & the cam setting on the throttle shaft. I started motor & let it warm good & rechecked everything. I decarbed 2 times sprayed seafoam in carb several times until it bogged down & then sprayed until it died. Filled clys. with seafoam rotated a couple of turns put plugs back in & let sit overnight. Took it out next day & ran it for 30 min. wide open it ran great. But, I let it idle for 30 seconds( the idle speed is low I need to turn it up a bit) & when I went to wot it still surges just like before & of course won't hardly move ( this is severe surging or hunting I call it). So I put it in reverse wot it ran good shifted back to forward & it runs great. This is not occasional I can repeat it ever time. The second time I decarb was on the water. And the compression only came up to 72 & 77. PS there was very little smoke when I decarbed I'm guessing from the results that the previous owner had already done it.
 
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234rick

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Re: 25hp hunts after idle

From what I can see on the head there is no discoloration & I can't feel any leaking around it.
 
14ftgrumman

14ftgrumman

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Re: 25hp hunts after idle

I'm agreeing with the seaFoam de-carb. Then tear into the carb.Let soak over night in carb cleaner, and blow out all passages with compressed air.

If problem persists, you migh want to concider rebuild on the power head. Have you pulled the cyl head or exhaust ports to check condition of cyls?
 
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jonesg

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Re: 25hp hunts after idle

If its a hand start you will not get much more than 70psi pulling it through by hand, if its elec start the compression is low.
Shifting into reverse shouldn't do anything different to clear it out unless theres a linkage problem somewhere.

You sure you aren't revvin it up in neutral to clear it out?

I would suspect the carb float isn't seating properly, allowing the engine to load up on fuel at idle. At WOT the excess fuel gets blasted out the exhaust.
Running rich will show up on the sparkplugs if you start out with new.
 
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234rick

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Re: 25hp hunts after idle

Its an electric start & I only pause in neutral before I put it in reverse, I don't use the fast idle. But I like the float suggestion because something strange is happening. Because it does it everytime I idle for more than a few seconds. I forgot to mention that it uses alot of gas 6 gallons in maybe 1 1/2 to 2 hrs of running mostly wot. That could be a float problem right ??? Is there any signs to look for for excessive gas usage ? Another thing does the engine rev fewer rpms in reverse, maybe I need to try to get it to run at half throttle. I think I tried that but I'm not sure. The plugs I took out were very clean, but I had just done the decarb so that cleaned them.
 
Mas

Mas

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Re: 25hp hunts after idle

I'm still concerned about the low psi...70 is very low! Any sign of water on the plugs?

Mas
 
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234rick

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Re: 25hp hunts after idle

The plugs look pretty clean but I don't see any water they feel like oil is on them. Is there a color change when there is water in the cylinders ? I'm not sure about how compression works in an outboard or any 2 cycle. My question is if my headgasket is blown between the 2 cylinders will the compression be low like mine 75 psi ? And if that is true then couldn't I test the compression with one plug still in, that should raise the compression if it is a headgasket should'nt it ?
 
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234rick

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Re: 25hp hunts after idle

234rick said:
???
Click to expand...

I was out yesterday & the timing was off 2 or 3 degrees so I adjusted it. I ran it wot for a little while & then idled & it still doing the same thing - surging after idling. Since the last post I have dune several things mostly just checking things, 2 decarbs,check all bolts, removed carb & adjusted float, check fuel pump, checked spark(good spark but I 'm not sure about the blue color its more like white), & much more. Everytime I go out the compression improves yesterday it was 103 & 107 so that i'm not worried about. I still can't get the surging fixed.
 
N

northwoodslivin

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Re: 25hp hunts after idle

Have you removed the jets to look at the tips very well to see if they are damaged? have you pulled the orfice plugs and run 120 PSI after cleaning out the carb through all of the passages from an air compressor? Sounds like your carb has some gunk in it. Do you have a fuel filter on the fuel line? Did you check the needle valve under the float?

Sounds carb related to me. I was getting some nasty surging in my 89 Johnson 20HP and it turned out to be that my idle jet had a bunch of junk in there.
 
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