Lost Proformance

Last fall I acquired '85 Sylvan Fish & Ski with a 90hp Evinrude E90TLCOS. First several outings it ran fine (this season) both at idle and cruising at 5200 rpm. Last weekend it developed a noticeable miss that seemed to disappear at higher rpm. While attempting to put it on the trailer it started the missing and stalled. Being it was on the trailer and dark I went home. [ Back up a week ~ Prior to the outing I was also experiencing a soft fuel bulb that didn't seem to want to pump up hard. I installed an anti-siphon valve on the top of the tank delivery line to the engine. I also found a leaking line from the fuel manifold to the primer pump which I replaced and didn't observe any other leaks.] So now I'm thinking the miss was due to fouled plugs or possibly week spark. I pulled the plugs and they all looked pretty good. While they were out I did a compression test and an 'open air' spark test. Compression was 110 to 108 and the spark look very strong. So I was thinking my miss was related to the poor fuel delivery with the soft bulb. I extended the fuel line to enable me to mount the fuel bulb vertically and replaced the fuel bulb. It did eliminate the solf fuel bulb issue and thought all would now be good. Today at the ramp the engine would start rather easily but then die. I could keep it running by giving it a 'shot' with the primer pump and after it warmed up it ran on its own but was missing. When I would lower the fast start lever and attempt to put it into gear it would die. I did finally get it into reverse and backed off the trailer. I pulled away and was going to blow out the cobwebs so to speak and found I had very little flat acceleration..maybe 2000 rpm. I turned right back and put it back on the trailer. Now I'm scratching my head. I've got new carb kits I was going to use this winter but maybe nows the time? Thoughts? Suggestions?

I'd do the carbs now rather than waiting. JMO

Those compression numbers are not encouraging.---Test again with another gauge.

What ever happened ??

Got put to work siding a house is what happened! lol Just got the carbs off today and rebuilt them .. not too encouraged that they were my problem. Carbs were really clean. I can only hope. We're getting the remnant of the storm out of the gulf and the river is expected to crest Monday at 40 ft., 4 ft over flood stage! It will be a while before I can get it back in the water. I'll run it on the hose when it clears up and see how it goes.

Hope you checked the high speed jets in the float bowls of the carbs. They are often overlooked.

They were found, .. passed a wire through them, sprayed them out with carb cleaner and blew them out with air .. throughout. Did locate a cracked hose from the primer pump to the carb .. believe I'll replace all those small vacuum lines from the manifold. Could those small "check valves" be part of my problem? Is there a means of function checking those?

Can't find the small (2mm?) vacuum lines locally and ordered from Ebay which seems to have been a mistake as they haven't arrived as yet .. holding up any progress of reinstalling the carbs.


While in waiting I read another post "Johnson 150 no spark" (9/06) brought to mind another issue which may be significant to my original problem. So I think it deserves mentioning for your consideration.


While out and the motor was running without any issue I noticed the voltmeter would stay above 14 to 15 volts at higher RPM. Other gauges were operating normally. Next time out (motor running fine leaving the dock), I noticed my voltmeter would run up to about 18 volts ! but would drop down in the normal range at idle. Also the speedometer and the Tach would cut out? It was on this very trip out when I noticed the motor was starting to miss some on start up as we moved while fishing. At the ramp it died, which is where this post began.


As I write it is occuring to me this may be more of my problem than the carb/fuel problem I'm currently addressing. As soon as my vacuum line gets here I can get the carbs back on and go from there. Any thoughts about the above info would be appreciated.

Ok, carbs are back on and replaced the primer line to upper carb. I hooked it up to the hose but no significant change in how it runs. As the engine slows to just above idle a obvious "pop" (not sure I would call it a backfire) can be heard out the prop exhaust. It dies at lower RPM and will stall if I attempt to put it into gear .. just as it was acting last trip to the water.

Wish I had $5 for every time I have read ----" cleaned the carburetors but motor still runs the same " on these pages.

You know racer I am grateful for this forum and the expertise it offers through the helpful advise of its contributors that keep us weekend boaters on the water but quite frankly we can get along just fine without your wise crack comments that insult our sincere efforts to describe and fix problems we have. Maybe you should quit reading these posts if your so bothered by them? The "help" you offer in the way of sarcasm isn't much help at all and better kept to yourself.

Well spoken Sam110 !!!!!!!

Perhaps find a shop that can do a " leak down " check on the cylinders.

Edit. Miss information that didn't suit racerone.

A " leak down " tester finds air leaking .-----Please explain why that does not work on a 2 stroke.-------On a 4 stroke air can leak out of the valves / past pistons and rings / out a defective head gasket.----On the 2 stroke motor in question there are no valves as the only difference.

I think its spark related. Lets pursue that. I feel Racer didn't mean as an insult. He is just explaining that may carb repairs are unneeded, and/or done improperly. When the motor has been running fine and suddenly there is a problem like you describe, it is more often our "electronic age" kicking in. Modern spark components are not predictable like fuel pumps and carbs.....unless you got some dirty or contaminated fuel. We know that most commonly, fuel issues otherwise happen over time and with alcohol fuel use. The compression is low, but as suggested, try another gauge. Make sure throttle is open so it can draw proper amounts of air. Especially important with 4 strokes. I don't feel that your compression numbers are low enough to produce those symptoms, surely not coming on so quickly as you describe. Lets check for spark, nice strong 7/16 or 1/2 inch blue......while symptoms are present. Good luck......Tim

Popping sound or backfire could be caused by a timing problem which could explain poor high-end performance.

So today I get back to looking for my problem. Once again checked compression and spark this time I opened up the throttle as Tim pointed out .. although I had to use the same tester. Compression was just above 110 in all 4 cylinders (tester reads in 5 lbs increments) and open air spark was strong at 7/16. Pulled the flywheel to have a look at the stator and timer base .. nothing obvious I can see with the stator but the timer base exhibits two elongated holes or tares(?) that I don't think are by design. See photos.

I removed the stator to test it at home with an Ohm meter but I have a problem removing the timer base as both harness connectors have a black and yellow wire that continues into the lume on the other side. I presume these must be cut and later connected to the wiring of the new timer base? See photos.

I'll need to do some research in my manual and watch a couple YouTube videos but any input would be appreciated.

In reading the manual on how to test both stator and timer base I discovered the wire I questioned are easily pushed out of the connector plug. Stator resistance check is within spec of the Ohms requirement. The timer base passes the port / starboard side "A" "B" "C" terminal test but fails the "A" to "A" test. Keeping my fingers crossed that a new timer base will cure the problem. Hopefully I'll know by next weekend. (river is still up and muddy anyhow)

Regarding the above test of the timer base / trigger I find that several sources for specs and testing of this component do not mention (require?) the A to A (white to white wire) test required by the Evin/Johns manual ? At $300 a pop and no chances of return for this part I want to be sure as possible that the timer base is faulty. Anyone shed any light on this for me?

Try testing the trigger while moving the wires around. The throttle movement presents a different situation and if a wire's conductor is breaking, you will then pick it up with the multi meter. I always try to perform trigger tests while moving the throttle with the trigger mounted in its place. Certain throttle positions will then "recreate" the intermittent problem.

So last weekend I took my timer base to my local marine shop and explained the above tests I've done and asked about the "A" to "A" test outlined in the manual. He was puzzled but tested it himself and said it was good .. that I needed to check it running with a voltage or DVA tester to be certain. Ok so I order a DVA module for my multimeter. It came thru the week and today I went thru DVA tests per CDI's trouble shooting guide for the timer base, stator, regulator/rectifier and all were within limits. I scrutinized the simplest things, replaced the plugs (which were the formally recommended alternate plug QL82C) with the QL77JC4 and seperated the plug wires from touching one another and .. and .. as embarrassed as I am to say it .. determined I had plug wires crossed !! [Hey, at least I admit it] I can only surmise the initial miss was with the poor fuel flow and dirty carbs. I must have crossed the wires when I did the compression check and the hell of the matter is I marked each top cylinder for that very reason! Since then I was relying on the marks to be legit. Dumb hua? Jokes on me . The biggest regret I have over this entire sogga is that I missed a beautiful day on the river with the wife and grandkids who were eager to use their new tube .. all because of crossed plug wires.. live and learn! I'll give it a 'clean bill of health' after I get it back on the water but yes, it's running fine on the muffs. Thanks all.

I always say, " it's the little things that will get you ".