1990 johnson 48 spl it did something weird

[smvarner]

Hello all got a problem with a 1990 johnson 48 spl and it did something weird model number is j48eslesa is on a 16ft lowe flat bottam was giveing to me by my uncle motor was rebuilt and only has a few hrs on it all on a set of muffs he ran out of money and it sat for about two years when i got it i had the carbs rebuilt and it ran fine at home but was hard to start in the water would not idel only ran with the high rev. lever pulled up all the way. could get it to go if i lowed the high rev. and quickly put in gear and went to about 1/4 to 1/2 throttle when it was running gas was sparying out the top carb my other uncle who was down said that was a sing of bad reeds so i replaced them could not get oe so went with aftermarket. So now for the it did something weird after installing new reeds i started it and all sounded good pulled the high rev. lever up it reved up let it run for a min. or two lowerd lever back down it slowed down some then reved up like it was at 1/2 throttle and stayed all linkage was at idel and butterfly valves where cloused on both carbs turned key off and it would not shout off now this is where i got worried and pulled the battery cables off still ran so next thought was pull plug wires off and guess what IT STAYED RUNNING with no spark plug wires so next off come the fuel line after the carbs ran out of gas it finally shut off. im not sure what to do now what would make it stay running after pulling the plug wires off. btw i thought the timeing was off befor i put new reeds in so i did the joe reeves wot timing procedure and comp. on both cyl. is just over 150 lbs any help would be much appreciated.

 

[Faztbullet]

Called runaway 4 stroking.......good way to break piston skirts

 

[oldboat1]

Scary (memorable, but rare). Best way to stop it is to cut off air -- jam a shop rag into the carb throat(s) on motors without an air silencer, otherwise the silencer intake.

Revving on muffs can be the culprit.

Pulling the battery cables likely shorted out your rectifier, so the motor may not charge (tach operation might also be affected, if you have one). When you get your nerve up again, idle it in the lake or deep in a test barrel. Check for charge -- if none, replace the rectifier (usually $40 or so). You do have to run it a bit above idle to see a charge, but don't need much over a fast idle to check.

 

[roscoe]

A runaway like you experienced can be caused by carbon build up.

At this point, pull head and inspect pistons and head, Adjust carbs, adjust floats, check rectifier function.

As stated above, kill the motor by cutting off air to the carbs.

 

[smvarner]

Hi all thanks for the info motor wouldn't fit in my old test tank building a new one now befor I try again roscoe with the motor having been rebuilt I didn't think there would be any carbon build up but I've been wrong befor this is the first outboard of this size I've worked on others were a 1960 Johnson 3hp and a 77 6hp not a lot of experience with 2 stroke mostly work on trucks and zero turn mowers. I was already thinking about pulling the head and intake to inspect for damage but was unsure will do a comp test first and look into a new head gasket befor i pull it. Btw I do have a repair manual and what could cause it to run good at home but not start when in water thanks for the help

 

[racerone]

Outline your starting procedure.----Sorry, on more than one occasion I have seen folks who where not using the correct procedure to start a motor.

 

[oldboat1]

runs good on muffs, stalls in the water -- think compression, spark, or carbs. I would do the compression check first, then spark testing with an adjustable tester. Carbs may need cleaning/rebuilding, or might just need idle needle adjustment (try the latter first -- might not have been dialed in after rebuild). When idling, pull off plug boots one at a time. If you pull a boot and get no discernible change in rpm, that plug is probably not firing.

 

[boobie]

The trick with this type of motor is not to over rev it in neutral.

 

[smvarner]

so did a couple things today compression test both cyl. 155 on both and both cyl. are getting fire will jump a 7/16 gap with a spark tester as the wot timing procedure i did said to check for if i get the time tomorrow ( its my aunts birthday ) i will see what the max gap it will jump also the spark plugs are new. i finshed the test tank today so will have it in water not muffs when i try again. i did find somethin out the carbs have different part numbers on them top one matches the 1990 48 spl the bottom one matches a 85 50 hp from what i can tell from part numbers on the metal tag on each carb and the top carb has a slow speed screw and the bottom doesn't what you all think can the two different carbs be part of my problem if i remember right the man i had rebuild the carbs ( did not have the time to do myself was in middle of mowing season ) said something about a little difference between them but they had the right jets in them for a 48 spl and should work fine. as allways thanks for all the help and on a side note anyone know a good place to get parts for what i've been told is a 77 force 15hp a family friend has asked for a little help finding parts.

 

[smvarner]

Hay racerone sorry about late reply waterpump went out in my truck starting procedure is lift up the high rev lever just a little and push in on key for a second or two while craking. which is what i was told by my uncle when i picked the boat up if i should be doing something different please let me know. anyone of an opinion on the carb difference i mentioned on my last post thanks

 

[racerone]

One carburetor has different linkages on it.---That is why it is given a different part number !----Check the flywheel key. if it is sheared it throws the timing out.

 

[oldboat1]

on a side note anyone know a good place to get parts for what i've been told is a 77 force 15hp a family friend has asked for a little help finding parts.

can find Chrysler/Force parts here on iBoats, NAPA, older local shops, etc.

 

[smvarner]

So I went to check flywheel key but my puller didn't fit have to make another one but could see the key under the nut and it looked fine. So I tried to start it in a test tank i built and no go would turn over but not start has compression 155 on both cyls. Checked spark on both cyl. Will jump a 7/16 gap on both nice crisp blue spark I did the wot procedure again to make sure nothing has changed and it hasn't I'm starting to think my problem is in the carbs can get another used set for $75 off eBay but not sure whatelse to do next

 

[smvarner]

By the way thanks for the info on where to get parts for the force outboard rebuilt the carb and it runs great now thanks

 

[racerone]

???----You can not determine a good / bad key by looking under the nut !

 

[Bosunsmate]

Rotate your flywheel to ODegs lining up with the pointer and check that your top piston is at TDC that way you can check your flywheel key without the struggle of removing it

 

[smvarner]

racerone i did't mean i had determined a good or bad key just what i had seen had planed on pulling the flywheel but i broke my homemade puller my half ass weld worked fine for small motors but didn't hold up to this. but i did do what bosunsmate said and the TDC mark lines up with the pointer when at TDC should i still pull the flywheel and check the key?

 

[racerone]

No, ---You have confirmed that key is not sheared.

 

[smvarner]

alright what should i look at next it has spark compression timming is right carbs were rebuilt is there something im over looking or should i try another set of carbs not sure where to go from here

 

[Bosunsmate]

Well whats the problem with it now? It might not run away on you again and you have replaced the reeds, time for another test.
Do a drop test on each cylinder if you think you still dont have power