91 Johnson 30 idles but will not accelerate

Jim Hatch · May 13, 2005

Recent purchase of marina maintained 91 Johnson 30 HP very low hours. Was running beautifully until Sunday when it suddenly would not run beyond a fast idle. It starts immediately and idles smoothly until gas is applied and it spits and sputters above fast idle. Assumed carb problems and just finished second rebuild. Same thing. Disconnected S.L.O.W. with no change. Pulling a plug wire one at a time, starts and idles with an obvious miss, hits hard and idles smoothly when plug wire reconnected. Carb looks like new and have run soft copper wire through all openings. Tanked carb 24 hours, reassembled, same thing. Starts and idles nicely. Have bought new tank, hose, in line filter, fresh gas/oil mix, flushed pump and hoses while carb off. Still will not accelerate. Compression 115 top and 112 bottom cylinder. Engine model J30REIC, ser G02603767. Not sure where to go from here.

OBJ · May 14, 2005

Re: 91 Johnson 30 idles but will not accelerate

Welcome to iboats Jim! Certainly seems you've covered most of the bases. Couple things to check, when an engine does what your describing, it sometimes is a mechanical thing. Pull the cover off the engine. Look at the carb cam follower...little roller attached to the intake manifold with a link to the carb throttle plate shaft. It's moved by the cam just under the flywheel. Have someone move the throttle slowly forward and watch the cam and roller. As the cam and roller meet, the throttle plate should just start to open. Make sure at WOT the throttle plate is flat across the carb throat. Fuel pump...disconnect the inlet hose or just take the filter cover off the pump. Take the hose off the outlet nipple and connect a short hose to the outlet nipple. See if you can blow back through the pump from the outlet nipple. If you can, most likely the pump has gone south. Fuel should only flow one way through the pump...from the inlet to the outlet. One more thing....take a timing light with you on the water. Run the engine and go to WOT with the timing light connected to one of the spark plug wires. Look for spark like this on both leads. The timing light should flash if spark is present. It is possible to have both spark at idle but lose one or the other at higher rpms. Stay in touch.

Jim Hatch · May 14, 2005

Re: 91 Johnson 30 idles but will not accelerate

Hey OBJ, Much appreciate the response. I checked the cam follower. The throttle plate just starts to open when the roller has traveled about 1 inch on the cam, not when they meet. At wide open position on the controls, the throttle plate looks to be about 80 percent open. Adjust the cable end to resolve this? On the fuel pump, I removed filter from top of pump, removed hose from carb and blew through it. Very tight, cannot blow through it in that direction. While hose was off, cranked engine over and got good fuel flow from pump. As to taking timeing light on water and checking with WOT, any throttle setting above idle results in engine slowing, spitting, sputtering, and shutting down. It will run smoothly at idle, maybe a fast idle. Will not run at higher throttle settings. Warm regards, Jim

Jim Hatch · May 14, 2005

Re: 91 Johnson 30 idles but will not accelerate

Hey OBJ, Found a general repair manual at the library. Local shops do not stock. I was able to properly set the throttle plate opening using the tick marks provided on the cam and the linkage adjustor. Will test soon as this thunder boomer moves through.*G* Warm regards, Jim

Jim Hatch · May 14, 2005

Re: 91 Johnson 30 idles but will not accelerate

Storm moved out. Hooked up the muffs and cranked the engine. Got it up to operating temp and tried to increase speed above idle. No luck. Still spits and sputters and sounds like the original threshing machine at anything above idle. Still looking for suggestions to resolve the problem. I know, getting close to the pricier solutions.*G* Story of my life. Gotta do it though. Any suggestions appreciated. Warm regards, Jim

G DANE · May 14, 2005

Re: 91 Johnson 30 idles but will not accelerate

I would recommend you to look at the spark on each cylinder when you start to raise RPMS , by hookong a timing light on, exactly as OBJ suggests in the last section of his post, good advise, your power pack on one of the coils may fail as is has to fire faster.

Jim Hatch · May 15, 2005

Re: 91 Johnson 30 idles but will not accelerate

Hi G Dane. Thanks for the advice. I was apparantly suffering brain fade or misread OBJ's initial reference. It makes sense to me now. Alas, a search for my old timing light was fruitless. Can't remember who I might have loaned it to. (Brain fade again?) Anyway, when the shops open this afternoon, I will endeavor to obtain a new one and check out the fire on the plug leads as you kind gents suggested. I'd be tickled if it turned out to be one of the coils breaking down.*G* I checked on this site for a new power pack and they do not appear to stock this model for the 91 30 hp. Coils are in stock though. Hope I don't end up needing a part that is "extinct".*G* Thanks gents. Hope to have more info to report this afternoon. Warm regards, Jim

Jim Hatch · May 20, 2005

Re: 91 Johnson 30 idles but will not accelerate

Hello Gents, I just realized engine is overheating intermittently while working on it using ear muffs for cooling. It had hit mud bottom at low speed on two occasions on the day the acceleration problems started. Engine pees intermittently and assumed thermostat was closing. Removed thermostat and no change. Blipped throttle very briefly on cold engine. No acceleration problems. Gets warm (hot), perhaps 1 minute of running, and will not accelerate. Tried opening cooling system with wire, water, and air pressure. Removed some of what looked like red clay from pick up tube. Impeller looks perfect but ordered new pump, thermostat, head and head cover gaskets, and new manual. Should all be here this afternoon. Will painstaking clean cooling system and install new pump, thermostat, head and cover gaskets. Looks like it's really gonna be tight torqueing lower three head bolts. May have to grind some length off of a socket to get it on the bolts and not binding with lower housing. Anyway, hope to aleviate any cooling problems first and if problem persists with acceleration, will pick up timing light and check plug leads as suggested in persuit of electrical problem. Thanks for your help. Warm regards, Jim

Jim Hatch · May 20, 2005

Re: 91 Johnson 30 idles but will not accelerate

Hey Gents, I installed new impeller, dealer did not have complete pump. Removed head, cleared all traces of mud from same. Made sure passages open. Water now flows freely from garden hose up through water pickup, and out below bottom cylinder as well as out tattle tale. Waiting on dealer to call when head gasket and head cover gasket get in. Will install head with new head gasket, head cover and gasket, and new thermostat and see what I have. Thanks! Warm regards, Jim

Jim Hatch · May 21, 2005

Re: 91 Johnson 30 idles but will not accelerate

Hey Gents, New head gasket and head cover gaskets installed. Pumping plenty of water and running cool now. Starts and idles well. Anything above idle the engine spits and sputters. Still have not tried timing light on plug wires. Son is bringing over his timing light tomorrow. I did check it with a cheap bulb type spark checker. Plugs onto spark plug and into plug lead. Bulb flashes each time plug fires. At idle, bright bulb flash. Advance throttle and bulb quickly dims down to nothing. Same on both coils. Is this comparable to the timing light test on the plug leads or do I still need to try that one? Or am I at the point where I should order a new power pack for my engine?*G* Ouch! Thanks Warm regards, Jim

fireman57 · May 22, 2005

Re: 91 Johnson 30 idles but will not accelerate

Check your spark on each cylinder and ground it to the block with insulated pliers and make sure that the spark is bright blue and will jump at least 7/16 - 1/2". If sparks are weak and yellow they will not fire under a load. If it is only on one cylinder you may be able to swap the coils and see if the problem follows. If it doesn't then suspect that coil. If it does than I would believe your coils are good and then you need to look further. Could be the powerpack.

Jim Hatch · May 22, 2005

Re: 91 Johnson 30 idles but will not accelerate

Thank You Fireman, I just read your post and went out and checked the spark. Spark is 1/2 to 5/8 on both coils. Color is blue.*G* Looks like the coils are OK. Appreciate the help. Warm regards, Jim

fireman57 · May 23, 2005

Re: 91 Johnson 30 idles but will not accelerate

Go to the link n sync part of your manual and do each step exactly as they say. May have something out of adjustment. Butterflies might be opening wrong time, etc...

Jim Hatch · May 24, 2005

Re: 91 Johnson 30 idles but will not accelerate

Thanks again Fireman, Did the link n sync bit. No change. Just ordered a new power pack from the dealer. I pulled the flywheel and all was clean and shiney. No sign of heat damage or any stray grease or water. Hope the power pack resolves it. Thanks much. Warm regards, Jim

N4WJT · May 24, 2005

Re: 91 Johnson 30 idles but will not accelerate

Originally posted by Jim Hatch: Thanks again Fireman, Did the link n sync bit. No change. Just ordered a new power pack from the dealer. I pulled the flywheel and all was clean and shiney. No sign of heat damage or any stray grease or water. Hope the power pack resolves it. Thanks much. Warm regards, Jim

N4WJT · May 24, 2005

Re: 91 Johnson 30 idles but will not accelerate

Jim, I'm very interested in what you determine. I have a '91 Johnson 48 Special that idles fine but when you get planed off starts to 'buck' with rpms slowing and increasing in cycles. If you don't pull back on the throttle, it will die. If you do pull back, it will idle fine. I think we may have similar problems.

Jim Hatch · May 24, 2005

Re: 91 Johnson 30 idles but will not accelerate

No Problem WJT, Will keep ya apprised. Warm regards, Jim

fireman57 · May 25, 2005

Re: 91 Johnson 30 idles but will not accelerate

Powerpack most likely will solve your problem. I just wanted to eliminate all we could before spending the big bucks on that part. When you pulled your flywheel was there any slop at all in the key? N4WJT make sure your flywheel key is not sheared.

Jim Hatch · May 25, 2005

Re: 91 Johnson 30 idles but will not accelerate

Hey Fireman, No slop noted in flywheel. I certainly concur in eliminating costly replacements that do not cure the problem.*G* Can add up in a hurry. Hope to have the new power pack in hand late this afternoon. The old one is off and all is ready for the new one. My gut feeling is pretty good on the power pack being the culprit, but it's great to have a place like this for advice in thinning the options. Much appreciated. If this resolves the problem, it will have been a valuable experience. I have learned how to clean/rebuild carbs, fuel pumps, adjust timing, and perform a number of system checks. Hopefully, before days end, I can add successful power pack installation.*G* Thanks! Warm regards, Jim

Jim Hatch · May 26, 2005

Re: 91 Johnson 30 idles but will not accelerate

Hi Gents, Finally got the power pack this afternoon. I installed it just prior to darkness. Hooked it up to the muffs and seems to be cured. Gonna double check everything in the a.m. and take it to the lake. Got the trolling motor battery charging just in case.*G* Thanks for the help folks. Great web site here and a nice bunch of people. This site is permanantly on my favorites list.*G* Warm regards, Jim

91 Johnson 30 idles but will not accelerate

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