Idle problems 1989 90hp Johnson

[outboardkiwi]

History to date: purchased boat and motor J90TLCEM 2 yrs ago and rebuilt motor after running and idling rough, traced to uneven compression due to coking. During rebuild replaced rings & honed bores, upper & lower crank bearings, all gaskets, seals, water pump, plugs QL82C’s, leads, coils, rebuilt carbs, fuel lines & filters, link & sync, checked recirc valves, Compression 10hrs after rebuild 125,125,130,131.<br /><br />To get this motor to idle in gear at 650rpm and out of gear out approx 800rpm I have had to bend the idle stop fwd and adjust the idle screw fully in. At this point, the cam and cam follower were aligned at the index mark and timing was 4deg, so I adjusted the cam follower pick-up timing to 5-6degs so at idle the carb butterfly’s are not open. Note also the idle is erratic jumping around 200rpm and sometimes dieing.<br /><br />I have also recently installed boyesen reeds and rejetted the idle air circuit down 5thou which made things worse, running rich so I reinstalled the original jets and rechecked the float levels etc. after which I ended back at the same point above. <br />Spark test also good on all 4.<br /><br />I figure that after studying the link & sync procedure for this engine that if the throttle valves are synchronized, wot timing is correct, cam follower pick-up is correct then a good idle should be able to be established at less than 4deg BTDC, failure to do so indicates the problem lies else where, ignition, fuel etc.<br /><br />This motor runs perfectly at low, mid and top end to 5600rpm any ideas on the idle problem would to gratefully received. Thanks. <br />

 

[rodbolt]

Re: Idle problems 1989 90hp Johnson

hello<br /> will it idle better if you start trimming it up? if it will remove the fuel bowls and place a straight edge across the fuel bowls. if its warped by the transfer passage between the fuel bowl inlet and the carb body it will run rich due to the fuel bypassing the needle assy.<br /> you can try surfacing the plastic bowls, find a set of used cross flow bowls or buy the metal bowl kits from BRP.<br /> I have surfaced more than one set but some are warped to bad.

 

[Dhadley]

Re: Idle problems 1989 90hp Johnson

I noticed you simply honed and replaced the rings. What did the cylinders measure after the honing was done?

 

[spucky]

Re: Idle problems 1989 90hp Johnson

Hi, on that model there is no timing stop. Adjusting the idle timing with the threaded knuckle also effects full advance.

 

[rodbolt]

Re: Idle problems 1989 90hp Johnson

spuckey<br /> there is a timing/throttle stop. see it bolted to the crankcase cover? there is no WOT timing stop. if all is correct then the idle pick up timing will be close when the WOT timing is correct. idle timing is usually not as critical as WOT timing.<br /> the tiny 5/16ths headed screw with a lock nut is a WOT throttle stop toprevent over stroke of the throttle shutters and to keep from jamming them at WOT.<br />outboardkiwi<br /> DO NOT adjust any timing other than WOT with the threaded rod attached to the trigger plate.<br /> the large screw that is just below the trigger plate rod sets the idle timing. the knurled wheel is for syncrhonizing the carb shutters.

 

[outboardkiwi]

Re: Idle problems 1989 90hp Johnson

Rodbolt, I will trying triming the engine up next time I'm on the water to see if that makes any difference. When I originally rebuilt the carbs I used sierra kits and noticed the other day when I had the carbs in bits again that the carb bowl to body gaskets were swollen and deformed so I refitted the original OMC gaskets that I removed when I first rebuilt the carbs.<br /><br />Can you order OMC carb kits for these engines, not overly impressed with the sierra kits.<br /><br /><br />Dhadley I'm not sure on the bore size, when I had the motor striped I took the block and pistons into a johnson service centre here in New Zealand and they honed the block and said quote "I should get away with a ring job" If I knew then what I know about outboards from this site and the world of parts available via the internet then I would of rebored. Maybe something to look at in the future as I am planning on keeping this motor for a while yet, but apart from being a poor idler this motor runs great.

 

[outboardkiwi]

Re: Idle problems 1989 90hp Johnson

Rodbolt, there is no WOT timing stop on this model and I have not touched the WOT timing via the top linkage since I set it up at 28deg, firstly by the Joe Reeves method then verified on the water. The cam follower pick-up timing I have adjusted so when the butterflies just start to open the timing is 5-6deg other wise if I leave at 4deg the butterflies would be starting to open at idle with the idle screw being screwed all the way in to get it to run. When I correct whats causing my problem I will set the pick-up timing back to 4deg.

 

[outboardkiwi]

Re: Idle problems 1989 90hp Johnson

Thanks for the info on the carb bowls rodbolt, I remember now that the motor idled ok when launching and retrieving the boat I guess because it was trimmed up. When trimmed down in deep water mode is when I had most of my problems. So I pulled the carbs today and yes the bowls are warped by up to .030” which I think is too much to try and surface so I will try and get new bowls. Our Johnson dealer here doesn’t know anything about the aluminum ones do you have a part number. I am going to an outboard wrecking yard tomorrow to see if I can find some secondhand ones. I have also ordered the oem carb kits. Hopefully on track to fit this one with your help. Cheers.<br /><br />

 

[rodbolt]

Re: Idle problems 1989 90hp Johnson

hello<br /> no part number on that kit. however you have to purchase new main jets or tap the new bowls to fit your old mains.and they retail for about 100 dollars apiece. almost any cross flow bowl from about 1970 or so will fit. the fuel inlets maybe different on some and the way the intemediate jet goes in the bowl may be different. some of the old carbs had a plug just above the main jet plug for the intermediate and yours the intermediate goes down from the inside of the bowl. wont make any difference just as long as you reuse all your jets in the proper holes. so most any cross flow v4 or v6 can be a donor from about 1970 or so to about 1985 or so.

 

[outboardkiwi]

Re: Idle problems 1989 90hp Johnson

rodbolt, I have found a set of 90hp v4 carbs from a 1994 motor on ebay, will these carbs or bowls suit my motor or carbs. Thanks.

 

[outboardkiwi]

Re: Idle problems 1989 90hp Johnson

Anyone know if 1994 90hp v4 crossflow carbs will fit a 1989hp 90 v4 crossflow. Thanks.

 

[reeldutch]

Re: Idle problems 1989 90hp Johnson

i'm not 100% shure but i think they should be pretty much the same.<br /><br />reeldutch

 

[outboardkiwi]

Re: Idle problems 1989 90hp Johnson

Rodbolt, I picked up some used aluminum float bowls today, we think off an earlier 90hp vro motor, the main jets I can replace with the ones from my originals bowls, as you mentioned in an earlier post, the intermediate jets are physically a different size but I think I may get away with it because the intermediates in the new bowls are 27’s and my old ones are 26’s so going slightly bigger shouldn’t be a problem?<br />I also noticed the actual bowl volume appears to be less, should I adjust the float drop to the figure recommended for the earlier bowls. Thanks again<br />

 

[rodbolt]

Re: Idle problems 1989 90hp Johnson

hello<br /> if the spec for float height is different I would use the spec for the replacement bowls.the difference between 26 and 27 jets is not worth playing with.<br /> hgope that helps solve the idle problems. its something that has plauged minlon bowls on cross flows a long time. if you lay a straight edde across the bowl by the fuel transfer passage you can see where the leak will be. it will leak fuel into the bowl bypassing the needle assy and then you cant regulate the bowl level so it floods. as you trim upit makes the chamber volume less due to the float design and will idle better for a time. post us a pic like the last one with a straight edge acrossed the bowlat the transfer passage area and see if we can see a gap.

 

[outboardkiwi]

Re: Idle problems 1989 90hp Johnson

Well good news, fitted the new bowls today and the 1st thing I noticed was the primer bulb would pump up nice and hard, prior to that it would pump up firm but with a little more force you could collapse the bulb. The actual idle has improved, its a lot smoother and I had to back the idle screw out about 1/2" from its previous position to obtain 750-800rpm out of gear and 600 in gear. I tried refitting the smaller idle air jets that I purchased when installing the boyesen's they only made it idle worse (rich) so I have reinstalled the originals for now. <br />Another thing I noticed while looking for any fuel leaks around the carbs was one of recirc lines was split at one of the valves, so I cut out the damaged piece of hose and refitted it the valve. I haven't received the oem carb kits yet so I may see more of an improvement when I install the kits. I'm off to the lake for easter weekend so will report back further on the motor after that. Thanks again OBK. <br /><br />Photo below of warped bowl around fuel inlet to needle and seat area.