91 Johnson 150 idles rough and dies when put in gear.

Old Coasty · Jul 25, 2005

Model J150GLEIS Faststrike. The motor ran fine, then at 80% throttle it stopped. It wouldn't start. After 15 minutes it started but wouldn't run above 2500 rpm. No warning horn but must have over heated. VRO was low on oil but never lost prime. Good stream of water from indicator. It starts good, idles rough in nuetral. Put in gear, idle goes down a few hundred RPM and dies. I changed the plugs but no better. If you idle at 2000 for a minute, drop back, put gear quickly it will runs ok at speed. Is there something I can try or should it go to the shop.

Seasport · Jul 25, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

Could be an airleak somewhere in the carbs. Check that all your jets are in place.

Old Coasty · Jul 26, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

Would an airleak be caused by overheating? I was going to check compression as soon as I can get a gauge. I took the plugs out after overheating. They looked carboned up, I cleaned them put them back in and ran it but it still ran rough. The cleaned plugs looked normal when I took those out after running. I then put new plugs in as mentioned before but it still is running rough and of course dying in gear. I was leaning toward a possible timing problem. Could the overheating have effected the timing.

Dhadley · Jul 26, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

Lets go back a minute. When you say it quit, did it just stop like you shut the key off and coast or did it lock up? When you say it wouldn't start would it turn over freely or was it locked up? What plugs are you using? How old is the fuel? Lots of questions but take your time and answer each one.

Old Coasty · Jul 26, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

I was crusing across the lake and it was like someone took the throttle and quickly put it back to idle but of course it died. It wasn't like key shut off. It never locked up. It turned over but wouldn't start. After sitting, it started but ran rough and would not acceed 2500 rpm. I took it back to the ramp at slow speed and parked it after this. I took out the plugs and they had crusty carbon on them. They were new in April. I cleaned them and started in driveway on muffs. It seemed to run ok, (in idle). Took to lake this weekend and it ran as describe above. The plugs are champion QL77JC4 0.030. I had the boat out the end of April in Tennessee for a week so the fuel is about three month old. I had it out a few times since then so there is about 1/3 tank now. I cleaned the fuel filter on the engine when I changed the plugs. The alarm may have gone off but I could not hear it because of it's location. Would it keep sounding with ignition on if engine is not running. I will check tonight to see if it's working.

Dhadley · Jul 26, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

Good choice on plugs but I'd get that old fuel out. Dont put new on top of the old. Youll just have more old fuel. Use fresh 87 octane. It almost sounds like we may have a pack or sensor going bad that threw it into SLOW and is keeping it there.

Old Coasty · Jul 26, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

It's not staying in slow. If I can keep it running when I put it in gear, (by doing it quickly and giving it throttle right away), it will run normal up full throttle. It does sound a little rougher though. It idles around 500 rpm now in nuetral. I think it used to be around 7 or 8 before this happened.

Dhadley · Jul 26, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

We may have lost spark on a cylinder at low rpm. If the top rpm is exactly the same as always, it may come back at or near wot. If the top rpm is off by 500-600 we may not be getting it back at all.

Old Coasty · Jul 26, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

I agree with loss of spark. I work on electronics for a living but don't know too much about outboards. Would overheating cause something to fail thus causing loss of spark? I will check spark this evening and I think I found a pressure gauge to check compression. I can only check with muffs at idle though. Anything else I can check to point us in the right direction? I will post finding tomorrow. By the way I want to thank you for your time and effort in helping me with this problem. I know a lot of people on this forum respect you for your experience and advice. I have read a lot of these posting lately and I want to tell you I agree with them. Thanks again!

Dhadley · Jul 26, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

Be careful with the motor running on the flushette if youre going to start pulling plug wires. That thing will zap you pretty good.

walleyehed · Jul 26, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

Oh my..I can't begin to tell how bad that hurts standing on wet concrete when "I" done that.....

Old Coasty · Jul 27, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

Well my worst fear was realized. 100 psi on four of the cylinders. The middle starboard was 58 psi and dropped slowely. The bottom starboard only had 20 psi and dropped to zero immediately. My next question is, am I looking at a new power head or does the heads and cylinders seperate from the crank housing.

Goodoleboy · Jul 27, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

You may only have a blown head gasket, Mite not be nearly as bad as you think. Hope so! Good luck!

Dhadley · Jul 27, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

That motor does not have head gaskets but we need to pull the heads off to see where we're at. Just out of curiosity, what plugs are you running?

Old Coasty · Jul 27, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

Champion QL77JC4. I will pull the head of the starboard side this weekend. I will post results Monday. Any advice or tricks I should know about.

Goodoleboy · Jul 27, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

Dhadley! Iam looking at a selco manual for 1973-1991 for all 3-4-and 6 cylinder motors. The exploded drawing for the v6 late models clearly shows head gaskets. Ill bet uh dollar your rite in saying this motor doesent have head gaskets. Its kinda scary tho, if we cant trust a manual any better than that. Please dont feel that Iam trying to argue with you. But if this manual is wrong, Iam throwing it in the garbage can. Its likely something Iam missing somehow.

Old Coasty · Aug 1, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

Well gentlemen the verdict is in, I pulled the head off, not good. The walls of the two cylinders in question are definately damaged. By the way, no gasket but there is an O-ring around each cylinder. I talked to the local shop here in town and he says he can rebuild for $ 2500. That includs pistons, machining, all bearings, carb rebuild, new vro pump, and water pump. I drop it off this week and should be back on the water by the 20th. Is there anything I should know or look out for when doing a rebuild. Any advice would be much appreciated.

Dhadley · Aug 1, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

OC -- The one thing you must find out -- what caused the damage? Goooleboy -- I'd bet the manual youre looking at doesnt cover the 60 degree motors. None of them have head gaskets. Its surprising how tough those O rings are.

Old Coasty · Aug 1, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

I was hoping that by having the carbs rebuilt, water pump and VRO pump replaced the culprit should be addressed. My theory is the water pump was at least five years old, (that's how long I have had the boat). It probably wasn't adequately cooling to start with. I had low oil level in the reservoir. I punched the throttle forcing the oil aft and the pump got air in the line for a couple of seconds.

Dhadley · Aug 1, 2005

Re: 91 Johnson 150 idles rough and dies when put in gear.

I dont think the low oil situation would do it unless it ran without oil for a minute or so at speed. However, thru all this you never mentioned the warning horn. I'd bet its not working. Make sure you get that looked at. It sounds more like a plugged carb(s) or old fuel.

91 Johnson 150 idles rough and dies when put in gear.

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