40 hp 2 cyl johnson 1 cyl idle

[DrinkingEmu]

1st year of boating, many questions, not sure of part names.<br />'92 40 hp Johnson model TJ40ELENM on 17 ft aluminum.<br />Bought boat used in winter, only saw it run on muffs<br /><br />Symptom: idle ng (rough will not stay idling drops below 850 when throttle is in home position then dies. Sounds like only 1 cyl idling) <br />-With carb air cover removed top carb "spits" Bottom carb fine (with throttle slightly on to keep motor running). <br />-Hand placed over top carb blocking air changes nothing, <br />-Hand placed over bottom carb stalls motor.<br />-Idle mixture screw for top carb changes nothing<br />-idle mixture screw for bottom carb modifies rpms<br />-Both plugs have good blue spark when pulled and grounded on block<br />-Both carbs taken apart, new floats (properly adjusted to // to carb body) soaked in seafoam for 1 dya then blown out the main jet, idle jet, and new float valve pin/seat<br />--pulled fuel line to see if vro pump was putting fuel to carb. (pump pours tons of fuel through)<br />Any ideas what I can try next? Please

 

[fireman57]

Re: 40 hp 2 cyl johnson 1 cyl idle

You might pull the fuel line to each carb and make sure that it is pumping fuel. Sounds like you have a low speed jet that is clogged or a float that is not adjusted correctly. You also could have lost spark to the top cylinder. Do a spark test.

 

[DrinkingEmu]

Re: 40 hp 2 cyl johnson 1 cyl idle

Originally posted by fireman57:<br /> You might pull the fuel line to each carb and make sure that it is pumping fuel. Sounds like you have a low speed jet that is clogged or a float that is not adjusted correctly. You also could have lost spark to the top cylinder. Do a spark test.

Hi I did those things. For spark test, is there more than taking the plug out, grounding it to the block and seeing the blue spark fire when the key is turned?

 

[wileecoyote985]

Re: 40 hp 2 cyl johnson 1 cyl idle

Your next check should be testing the compression on both cylinders. <br /><br />I suspect that you're going to find the compression low on the upper. Hope I'm wrong.<br /><br />Let us know what your readings are.<br /><br />Gary

 

[DrinkingEmu]

Re: 40 hp 2 cyl johnson 1 cyl idle

I do not have a compression gage. When I hold my thumb over the spark plug hole, both cyls feel the same : ) (blows my thumb back and burns it)<br />Is there anything special about a compression gage I should know before I go buy 1?

 

[fireman57]

Re: 40 hp 2 cyl johnson 1 cyl idle

There is a thread for a homemade spark tester that works very well. Do a search for it. As far as a compression tester you can get one real cheap at your local DiscounteverythingAutoParts store. Are both plugs wet with fuel when you pull them? Just because the fuel is getting into the carb doesn't mean that it is getting out of it. If a cylinder is not getting fuel then it is not getting lubrication either. I hope (and so does wilee) that this was not the case.

 

[DrinkingEmu]

Re: 40 hp 2 cyl johnson 1 cyl idle

Checked compression:<br />top cyl 100<br />bottom 120<br /><br />OK, last night took out boat after some mods.<br />moved motor up 1 hole, and added some stuff:<br /><br />still can not get to idle, but<br /><br />87 octane 2/3 full tank<br /><br />Prop 17P aluminum Michigan(banged up came with boat)<br />GPS 29.1 with wind <br />GPS 27.9 into wind<br />RPM 5400 (better than the 4900 before)<br />40 hp '92 johnson on tracker tx17 (mod v)<br />6 inch cmc tnt aluminum plate pt130<br />plastic trim wings (proper term ???)<br />slight porpise so had to trim down, boat felt like it rode much higher <br /><br />Prop 15P aluminum Johnson (borrowed to try)<br />GPS 27.2 with wind<br />GPS 26.5 into wind<br />RPM 5800<br />40 hp '92 johnson on tracker tx17 (mod v)<br />6 inch cmc tnt aluminum plate pt130<br />plastic trim wings<br />better hole, but that last 2 mph felt like a loss of 10mph. <br /><br />Any suggestions regarding idle, seeing as it seems to run ok at wot ?

 

[voodoo]

Re: 40 hp 2 cyl johnson 1 cyl idle

I think you'll find it difficult to get an idle with that big a difference in compression.<br />Pull the head and inspect.<br />I too am just outside Guelph.

 

[steelespike]

Re: 40 hp 2 cyl johnson 1 cyl idle

Carb spitting could be reed valves leaking.Or possibly carb flooding.

 

[DrinkingEmu]

Re: 40 hp 2 cyl johnson 1 cyl idle

Hi voodoo, What type of thing would I be looking for if I pull the head?

 

[voodoo]

Re: 40 hp 2 cyl johnson 1 cyl idle

Scratched cylinders, burnt pistons.