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Johnson 50 Idle issue J50TELCEC

T

TylerVDB

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Did some performance stuff over the winter, reeds, stuffers, milled head .010, velocity stacks. 89 50hp 2cyl J50TELCEC. Compression was 140 before I milled the head, now it’s 168. Spark is fine, jumps 7/16 gap. With this amount of compression I now run 93 as recommended by omc tillers on Facebook. 90 non-ethanol is not available around here.

Having a heck of a time getting it to idle without maxing the idle timing screw out which in turn screws up my link & sync. This started last year, NOT after the mods. I figured I had a carb issue so I cleaned them, didn’t see anything out of the ordinary. I did the reeds because I had a severe amount of fuel spit back. When I removed the manifold I could see daylight through 8-10 reeds with measurements .011-.012. They were bad. It seems pig rich at idle. Runs perfect off idle up to WOT. Plugs are a nice tan after a WOT run. Gained tons of mid range after mods, not too much up top, maybe 1-2mph, it’s on a heavy boat though. Definitely runs better than it ever has off idle. Thought I had floats set wrong, took the carbs back apart at the ramp twice yesterday. I cleaned them again last week to just see if I missed something. Seems to like 3 to 3 1/2 turns on the idle air valve needle. Carbs are part #432986.

In the last few years I’ve done everything but rebuild the powerhead and pull the flywheel for anything related to timer base/stator/pickup etc, all are still original. I’ve done all new fuel hoses from tank to carbs, new fuel pump (deleted VRO), new fuel distribution block, new fuel tanks, new primer choke solenoid, new coils, new plug wires, new starter, complete carb rebuilds 4-5 times over the years, new oem primer bulb, rebuilt tilt/trim unit, new rectifier, new thermostat, new impeller kit, new gearcase seals, ccms reeds, reed block stuffers, milled head a bit, velocity stacks. I’ve checked all fuel connections, everything is tight.

Not sure where to go from here. It idles really well with the idle timing screw maxed out. 750ish in gear. I’m just not sure I like how far that moves the timing cam roller away from its marks and messes with my link & sync.

I’ve ran this motor for over 10 years so I know how it’s supposed to run and idle in stock form. Have always done my own work. There are no Johnny-rude mechanics around here anymore. I still feel like I have a carb issue in the idle air circuit or a link & sync issue.
 
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“. 90 non-ethanol is not available around here.”
People seem to have a misguided hate on for ethanol fuel. Yet they will pay top dollar for something like Seafoam, & happily add it to their fuel. It’s an expensive way to put some ethanol into a fuel system.
All alcohols are very good solvents, they keep things clean, the reason cars will go 25+ years, & hundreds of thousands of km without ever changing or cleaning a fuel injector. They are also very good at moving small amounts of water through the system.
Ethanol does give a very small power reduction, but there are really only two detriments.
Legacy systems using old school gaskets/fuel lines etc, which are not alcohol tolerant- not the case with your ‘89.
The other, leaving ethanol fuel sit- it’s hygroscopic & eventually absorbs all it can hold & phase separates, if you use your fuel on a regular basis, there is no issue.
“not too much up top”
That is to be expected. In power engineering, speed increase is not a linear equation, it’s more like logarithmic. If you want to go twice as fast, you need 10X the power. Aerodynamic drag is also not linear, it’s a squared function. Twice the speed makes for 4X air resistance.
 
Edchris177 said:
“. 90 non-ethanol is not available around here.”
People seem to have a misguided hate on for ethanol fuel. Yet they will pay top dollar for something like Seafoam, & happily add it to their fuel. It’s an expensive way to put some ethanol into a fuel system.
All alcohols are very good solvents, they keep things clean, the reason cars will go 25+ years, & hundreds of thousands of km without ever changing or cleaning a fuel injector. They are also very good at moving small amounts of water through the system.
Ethanol does give a very small power reduction, but there are really only two detriments.
Legacy systems using old school gaskets/fuel lines etc, which are not alcohol tolerant- not the case with your ‘89.
The other, leaving ethanol fuel sit- it’s hygroscopic & eventually absorbs all it can hold & phase separates, if you use your fuel on a regular basis, there is no issue.
“not too much up top”
That is to be expected. In power engineering, speed increase is not a linear equation, it’s more like logarithmic. If you want to go twice as fast, you need 10X the power. Aerodynamic drag is also not linear, it’s a squared function. Twice the speed makes for 4X air resistance.
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I’ve never had a problem with ethanol fuel if I do my due diligence to the fuel system each winter. You still get the random person demanding the use of non-ethanol in 2026 though. Never made sense to me, cars have ran e10 for years.

My original plan was to throw a 56ci 70hp on the hull for some more mph and more bow rise. I’d like to see 40mph on this hull. I was talked into trying some performance mods since this 50 is one of the better ones and it would give me some bow rise. Didn’t do much speed wise (was 29ish, now 31ish on a 15 pitch prop) but it does run better than ever before minus this idle issue I’m chasing. Midrange is now amazing, has the low end grunt it never had, gave me the bow rise I needed. I still may throw a 56ci 70 with these same mods or a yammy 80 on it in the future. The hull is in too good of shape to get rid of and it’s rated to 80hp.
 
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Weight is the killer. You mentioned “heavy boat”. The heavier the boat, the bigger the hole in the water, & the greater the power required to overcome that.
Going from 31 to 40 is almost a 30% increase, power, (50-70), is 40% increase. It’s only time & money, if I was really set on 40 mph, I’d eliminate one step & go right to 80hp, then experiment with trim & props.
 
Edchris177 said:
Weight is the killer. You mentioned “heavy boat”. The heavier the boat, the bigger the hole in the water, & the greater the power required to overcome that.
Going from 31 to 40 is almost a 30% increase, power, (50-70), is 40% increase. It’s only time & money, if I was really set on 40 mph, I’d eliminate one step & go right to 80hp, then experiment with trim & props.
Click to expand...
Agreed. I’ll max the hull out eventually. The cost of a new boat vs tinkering with this one is astronomical, so I see no reason not to. Our saying around here is maintenance or payments and sometimes you get both lol. This hull has been garage kept its whole life, it’s an excellent condition aluminum Tracker V17 tournament.

Weight wise, yeah she’s heavy with what I have in it. 3 group 31s, 3 graphs, 12gal of fuel, lots of tackle, big trolling motor up front and I always have a passenger.
 
So today I took it out with a timing light. 8 degrees at idle in gear, 750rpm with the idle timing screw maxed out. I redid link & sync thinking I missed something. Still came to the exact settings to get it to idle stable in gear.

Now here’s where it gets weird. WOT throttle timing is 16btdc, 5200rpm. Granted I don’t have the timing test prop but still. The spark control rod is maxed out (clockwise). I should have some insane timing number with it maxed out the way it is. I’m starting to think the flywheel key is sheered or I have a failing timing charge coil. I should be able to get more than 16 degrees out the spark control rod. It calls for 19 +/- 1.
 
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