91 200 johnson will not stay running under load

[tampaaquasport81]

iv got a 91 200 jonson looper that will not stay running when in the water but will on the hose. the motor idles fine and then ignites and tries to cut itself out. when i try to give it throttle in gear most of the time it will die but for the times it doesn't it will clear itself out and want to get on a plane seems to run fine. i launched on a river so i can't get on a plane to see. so far i have replaced the power pack, timer base, wires, swapped out vro pump with used one, the old timer base had a pit about 2" long on the insid when i replaced it. i figured by replacing the timer base it could have affected the timing so i adjusted that bt didnt do anything. fuel is changed to premix 50/1 and i put new gas and water seperator in about 3 months ago. i checked to see if maybe it wasn't getting fuel by priming while throttling and it didn't help..

 

[ezeke]

Re: 91 200 johnson will not stay running under load

What are your compression readings?

Try running on a portable tank with fresh premix.

Disable the shift assist temporarily by disconnecting the ground wire but be careful around the dock because it may be hard to shift into reverse.

Did you disable the QuikStart advance when you set the timing?

 

[tampaaquasport81]

Re: 91 200 johnson will not stay running under load

compression on al 6 are 75-78psi and not sure what the quick start is? in a last ditch effort b4 i put the boat up i adjusted the timing by twisting the handle.il look in my manual and try disconnecting the ground from shift assist. i forgot to mention that the boat does not stay idling either it builds up and backfires and dies unless i can clear it out by revving in neutral then loads up after a couple secs. also i just took the spark plugs out and compared them. the right 3 seem to be more charcoaled then the left 3.. the boat came with ngk R plugs could that have anything to do with it.

 

[tampaaquasport81]

Re: 91 200 johnson will not stay running under load

the only time the engine seems fine is when it is hooked upto a hose and not in the water with a load on it...

 

[Dhadley]

Re: 91 200 johnson will not stay running under load

If it were mine I'd start with cleaning the carbs. Then get the right spark plugs in it and do a good decarb job.

If you're trying to get the motor to idle at 600-700 on the hose it will dies when in the water (backpressure). It'll idle about 1100 or so when on a hose. that should put you at about 650 in gear, in the water.

 

[tampaaquasport81]

Re: 91 200 johnson will not stay running under load

dumb question... but can i just take carbs apart clean and put back together, or do i have to buy a carb rebuild kit?

 

[tampaaquasport81]

Re: 91 200 johnson will not stay running under load

dumb question... but can i just take carbs apart clean and put back together, or do i have to buy a carb rebuild kit?

 

[Dhadley]

Re: 91 200 johnson will not stay running under load

You'll need to take them apart and soak them in cleaner. Then install new kits.

 

[tampaaquasport81]

Re: 91 200 johnson will not stay running under load

does that seem like the carbs could be the problem? any other ideas if that doesn't work?

 

[jim_b_20653]

Re: 91 200 johnson will not stay running under load

Your compression seems pretty low. You should try a decarb to see if that will free up your rings.

 

[Dhadley]

Re: 91 200 johnson will not stay running under load

I'd still do things in the order I mentioned. Clean the carbs, get the right plugs and then decarb.

 

[tampaaquasport81]

Re: 91 200 johnson will not stay running under load

im in the process of ordering the parts now, but don't have manual with me, tried to find carb kit for 91 johnson 200 but couldn't find one for that year is it the same as 90 or as 92, and do i need to order 6 kits?

 

[tampaaquasport81]

Re: 91 200 johnson will not stay running under load

also, carbs were rebuilt about 7-8 mos. ago. is there anyway to find out if they are in need of being rebuilt so i dont have to fork out $120+ ?

 

[Dhadley]

Re: 91 200 johnson will not stay running under load

Pull one / all of the screws that cover the hi speed jet in the bowl. If the inside is clean it's probably OK. If they were cleaned 7 months ago and have been sitting with untreated fuel they'll, most likely, need to be cleaned again.

 

[ezeke]

Re: 91 200 johnson will not stay running under load

Pull the thermostat on the right bank and make sure that the system is working; the big bore loopers hate running cold.

What is your idle RPM when warmed up, in neutral, and on the water?

 

[Faztbullet]

Re: 91 200 johnson will not stay running under load

Are you having a lean idle spit(phifffttt) back thru carbs also?

 

[tampaaquasport81]

Re: 91 200 johnson will not stay running under load

my tach isn't working but i'd say it is idling about 800rpms' whatever it is, when it is idling it sounds to be about right pitch. and faztbullet... yes it does the (phifffttt) back through the carbs. the motor is on premix, will it still do that? it happens about eveery few seconds and tries to stall and if i give it throttle after it make that sound it seems like it floods it... priming it doesn't help either

 

[tampaaquasport81]

Re: 91 200 johnson will not stay running under load

also, it runs fine on the hose but when it is in the water, it shows its symptoms... when i first put the boat in the water th e last time it seemed to idle fine for about the first 30 seconds then didnt want to stay running especially in gear..

 

[tampaaquasport81]

Re: 91 200 johnson will not stay running under load

i took a look at the carbs today, and were brand new from 6 mos. ago, fuel smelled fine bowls were full and seemed to be ok.from what i could see, but i didnt completely disassemble

 

[Faztbullet]

Re: 91 200 johnson will not stay running under load

The reason I asked about the (phifffttt) is I am seeing quite a few of the Johnrude's having this problem. What I have found is the rubber coating on reed blocks cracking(E10 fuel?age?) and causing reeds not to seal. Back engine in water and remove cowling and front cover ,trim motor so its level and start. Watch carbs to see which one it phifts from. Take a wooden tooth pick and plug the jet @ the 8oclock position on that carb ,if pift goes away it's not reeds but jet,carb,or gasket problem.