Slight Misfire 1999 Johnson 200

[atc250r]

Since shortly after I got the boat in November 2010 it would sometimes "sputter" at part throttle, then if I would pedal the throttle it would go away. It almost sounded like a drag car getting on the stutter box before it launched. It was one of those things I meant to get to but since it would go away so easily I didn't do much about it. I put new OE spec plugs and a set of wires from Bob's Machine on it at the beginning of last season but that didn't seem to make a difference. At the end of last season the one weekend it would do it at WOT as well and instead of turning 6000 like it usually does it would only turn 5700-5800. Went out for the first ride of the season the other day and it is still doing the same thing. It seems like I can get rid of it at part throttle by pedaling it but at WOT it happens pretty much all the time. My only guess would be a coil pack going bad. I'm not much of an OB guy, grew up wrenching on cars, and I/O's but I'm figuring maybe run it on the muffs and spray water from a spray bottle on one pack at a time to see if one of them starts missing. Thoughts? Suggestions if that doesn't work? The boat has an occasional miss and spit out the exhaust at idle too but very slight.

Just a little background, the powerhead is a 1999 Johnson that was rebuilt, put on a 1993 Evinrude bottom end, and sold by a member on S&F to the previous owner of the boat. The guy that sold/built it used to sell a lot of engines on there but seems to have disappeared from the site though. His name on there was Bigobass, I think his real name is Brad and he's from down in Florida. No beef with the job the guy did, it seems to run pretty well except for the miss but idles a little high and he sold the motor like 3 years ago so I'm only mentioning his name to see if it rings a bell with any of you as a particularly good or bad builder.

You can hear it "stuttering" at around 19-21 seconds in this video if it helps at all:



Thanks.

John

 

[john lamon]

Is it a misfire for sure or is it starving for fuel? usually if you can make it go away by pedeling it it's fuel, ever clean the carbs on it?

Edit: Just a guess but it could be throttle position sensor is out of adjustment or NFG.

 

[atc250r]

Never tore into the carbs. I figure if it was an issue like that it would lay down but not sputter plus its a fairly fresh rebuild. No TPS on these motors AFAIK. Got a set of Chris Carson reeds sitting here for it, if nothing ignition related turns up I'll look in the carbs while I have them off. I just don't want to do any other mods until I can straighten this issue out.

John

 

[paulsboats]

sounds like a fuel thing. crap in the bottom of the tank maybe

 

[paulsboats]

sounds like a fuel thing. crap in the bottom of the tank maybe

just guessing as i just had a customer come in had been to the marina several times the changed jets ect to the tune of 1700.00 asked me to change tank but wanted to go fishing today! so i popped the sending unit out and took six gallons of fuel from the bottom out after i tiltet the bow up as far as i could get it. there was chunks of rubber hose,leaves sea weed, water,chunks of rust from the pipes at the gas station ect. i orderd the tank for him and now its sitting in the shop. wot is when it gave him the problems the most as all the crap went towards the pickup then

 

[atc250r]

I've got a water separator on it with a new filter installed for this season. Maybe its a restriction? I'll bypass that and see what happens. I'm going to assume the carbs have to come off to clean them.

 

[atc250r]

I'll pop the sender out and pump the fuel out and have a look in there this week.

 

[propshafted]

still running the vro? would check fuel lines for ethanol damage. if your running electric pump, it's usually best to remove anti syphon valve in tank.

 

[atc250r]

I believe 99 was post VRO. Its still injected but they called it something else and used a different system. Fuel lines from tank to filter under cowling are all new last year when the separator went in. No electric pump.

Oh, and yes, the separator is plumbed correctly.

 

[john lamon]

I believe 99 was post VRO. Its still injected but they called it something else and used a different system. Fuel lines from tank to filter under cowling are all new last year when the separator went in. No electric pump.

Oh, and yes, the separator is plumbed correctly.

My 96 200 was post VRO as well, mine acted kinda like yours one time but it was as simple as changing one spark plug and it was back to normal, since you already did that I dunno? does it work better cold and get worse as it warms up?

 

[Rob B]

Maybe the fuel pump needs rebuilding. My 200hp merc (on the Pulse 170)was doing the same thing after trying everything else ended up the fuel pump was going bad. Just a thought.

 

[atc250r]

I'm gonna throw a set of new plugs in it and see what happens. From there I'll look inside the tank and bypass the water separator. If those don't do it I'll put an electric pump in like Wildman uses in lieu of a primer bulb.

John

 

[propshafted]

missed the 99 model, so it's ficht injected or carbed?

 

[denis leblanc]

Hey!! when you are running the boat at full throttle and it starts to sputter shut the engine off in gear wright away and let it cost to a stop, take the plugs out and see if they are dry or wet whitch ever one that is dry its a fuel problem on those cylinder if it is wet it is a spark problem on those cylinder sometimes spark problem is cause by timming or a coil wire on that cylinder or the magnito sending unit is defective (under the flywheel). But if you are having a dry problem is the fuel pump fuel opperates on crankcase vacum check to see if you do not have a crankcase seal leak to check that when the engine is running at idle chocke the carbs with your hands it should shut off within seconds if it keeps on running there is a vacum leak. Sometimes on a fresh rebuild engine the compression is so strong that you blow a seal slightly.

 

[atc250r]

Propshafted - it is a Johnson powerhead so it is carbed thank God.

Denis - Thanks for the suggestions.

I was thinking that the next time I was out and it started doing it I would push in the key to give it some fuel and see if that makes a difference. Might give me an easy indication if its a lean condition.

 

[RNGRDVE]

Use caution removeing plugs from a hot engine, if the heads are aluminum they can warp when plugs removed while hot.

 

[atc250r]

Yes sir. The threads can pull out with the plugs too. Lots of antisieze on these puppies always.

 

[denis leblanc]

Propshafted - it is a Johnson powerhead so it is carbed thank God.

Denis - Thanks for the suggestions.

I was thinking that the next time I was out and it started doing it I would push in the key to give it some fuel and see if that makes a difference. Might give me an easy indication if its a lean condition.

If you are at full throttle pushing the key in will not make a difference because at full throttle you are running on the main jets in the carb if you are at 0 to 1/4 throttle then you are running on the pilot jets and pushing the ket in will make a difference just remember to check the plugs for dry or wet

 

[atc250r]

I was always under the impression that pushing the key in forced fuel through an orifice that would prime the motor. Shows how much I know about these things. I gave the plugs a once over tonight and they all looked pretty much good, a nice chocolate brown. Of course, the real test will be after I do a plug chop the next time I can get out on the water. Since its easy to do and I can do it right in the driveway I'm going to run it on the hose and give the coils a little squirt of water one at a time and see what they do.

John

 

[denis leblanc]

I was always under the impression that pushing the key in forced fuel through an orifice that would prime the motor. Shows how much I know about these things. I gave the plugs a once over tonight and they all looked pretty much good, a nice chocolate brown. Of course, the real test will be after I do a plug chop the next time I can get out on the water. Since its easy to do and I can do it right in the driveway I'm going to run it on the hose and give the coils a little squirt of water one at a time and see what they do.

John

No john running the motor on the hose does not put a load on the engine so you will not have the same reading but you can still do the carb test at idile on the hose, remove the air box and place your hands on all the carbs when running at idle it should shut off on its own in sec. if not like I say you have a crackcase leak try that and if thats ok go do the other test on the water