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1995 Johnson 90 Cross-Flow V4 idle problem

M

mjedlin66

New member
I have a 1995 Johnson 90 cross-flow V4. It runs great... when not idling.

Sometimes it will idle fine when I first start it. Then I can run on plane all I want, but when I come back down to idle it will die. It starts right back up but i have to use my neutral rev lever to get it to start, then i have to shift into gear hard and immediately go at least half throttle.

Here's what I know so far. All of the work I have done was with OMC parts.

Compression test showed really even, 125 +/- 5 psi on each cylinder
  • I have replaced the spark plugs several times. I am using Champion QL82C gapped at 0.030"
  • My fuel is fresh ethanol-free 87 octane. I have burned like 10 tanks worth of fuel so I know it is fresh fuel.
  • I have drained my water seperator.
  • I have replaced all of my fuel lines going to the engine. I did not replace the fuel lines under the cowl.
  • I have replaced my primer bulb.
  • I have replaced my fuel water/seperator filter as well as the inline filter under the engine cowl.
  • I have rebuilt my VRO fuel pump (yes, I am still using VRO).
  • I have torn my carbs apart, found them completely spotless, and soaked them in a solvent tank for two days anyway. Rebuilt with OMC kit. I did take out the soft plugs, clean in there (also spotless), and replaced the soft plugs.
  • I have inspected my reed valves. None of them were broken, cracked, or chipped. I was curious if they would warp under heat so I ran a heat gun over them. I could see light through three petals, but only if i blocked off all other light. From the top-down inspection, they looked just fine. I think these are probably fine, but this *may* be the issue. I have no experience evaluating reed valves. I couldn't get new ones before I needed the boat again, so I re-assembled the engine with the same reed valves and new gaskets.
  • All of the gaskets from intake manifold to carbs are new.
  • I took out my four recirculation check valves. They seem to be working (they only flow one way). I cleaned them in my solvent tank. A couple of my valves have a dark black in the center of the screen which i suspect is dried fuel deposits. I was unable to get these screens clean. They tested okay though, so I put them back in. I did buy four new check valves to install as my next step. I blew out the nipples on the engine heads and they flow fine.
  • I have done a full link & sync every time I messed with the carbs. I have timed it using the Joe Reeves method to 24 degrees, and my spec is 28 degrees. I am confident the throttle plates are both fully closed at idle. The throttle cam contacts the cam follower at 4 degrees timing per the manual.
  • I have replaced all spark plug wires. I have verified that all of my spark packs are jumping a 7/16" gap healthily.

I am thinking it's gotta be down to one of these-
  • Reed valves
  • Recirculation check valves (about to replace all of these)
  • Crankshaft seals

I do own a leakdown tester. I have read conflicting info about what a leakdown tester can tell me. But if nothing else, I think pressurizing one cylinder with the piston at bottom dead center would allow me to follow the noise. Where is it leaking? Exhaust yeah, but where else?

Any suggestions?

Thanks
Matt
 
It won't let me edit post...

Model J90TLEOR

Final addition, turning in the idle stop screw for the timing plate does not cause my idle speed to go up. I tried it today per the manual, in gear, forward, in the detent. It was roughly 500 rpm and I turned the screw in like 10 turns and it didn't change the idle speed. Yes, I could see the idle plate moving. I am confident the spark was advancing, but the engine didn't speed up.

Also, when my idle is rough, pushing the key in to squirt fuel in causes the engine to die immediately.
 
If you test with piston at the bottom of the cylinder the air will simply rush out the exhaust ports.----That test will prove nothing !!
 
You might check to see if the bowls of your carbs are warped if they are plastic. They can have an air leak without a gas leak showing.
 
I can't attach photos. Today I started and idled it for several minutes. On muffs it appears that the idle timing screw DOES change the idle speed. That's interesting.

It stalled once, which happened while I trimmed down. I thought I was onto something. I restarted the engine and was unable to get it to stall due to any trim.

I tried the cardboard spit test at the carb throats. After ten minutes of idling with a sheet of cardboard held 1/2" in front of the carb throats, my sheet of cardboard was clean. That is supposed to suggest that my Reed valves are good.

I noticed the two brass passages at the bottom of each carb intake had milky white substance in them. It looked like they were full of water/oil. I don't know where water would be coming from, since I just rebuilt the carbs. I guess I will check my oil water seperator again. I blew the passages out with carb clean. They weren't clogged at all, just appeared to be filled with some white liquid. I know these passages were clean and clear in the carb overhaul. I wish I could post a photo of what I saw.

About to change my recirc valves I guess.
 
The idle speed on that motor is adjusted using timing. On a warm motor you want to be at 650 in gear or around 1100 on muffs.
 
Post pictures of this crack.----Your location ?----Hard to think there would be a crack as there is not much load on that manifold.
 
Last edited:
racerone said:
Post pictures of this crack.----Your location ?----Hard to think there would be a crack as there is not much load on that manifold.
Click to expand...

I agree that it doesn't make sense for there to be a crack here. But there it is. I can't figure out how to post photos on this forum.

The crack is in the intake manifold, in the top of the lower carb riser. The crack is where the riser transitions to the backplane of the Manifold. The crack is about 1" long and it is deep. I think it goes through to the small channel passage that is cut into the back of the Manifold.

I noticed it because right after running the engine I went to take the carbs off. The engine was trimmed down in the front. There was fuel pooled up on top of the lower intake riser, and it was butting up against the carb gasket. That lead me to the crack. I trimmed the engine backwards and sprayed carb cleaner to pool it on top of the crack. It drained into the crack.

Manifolds are cheap on ebay but I am taking this boat out Saturday. So I am going to grind the crack into a V shape and JB weld it. My thinking is like yours, not much stress here, so this repair will probably outlive the engine.
 
The paint or powder coat on this Manifold was super thick. That crack may have just been in the coating. As I ground it away, I became less certain that there really was a crack here. I JB welded it anyway.

Now I am replacing circ valves and we'll see tomorrow.

 
I often see these thick layers of paint cracked.----They have made thousands of those intake manifolds.----The metal just does not crack like that.
 
racerone said:
I often see these thick layers of paint cracked.----They have made thousands of those intake manifolds.----The metal just does not crack like that.
Click to expand...

You're probably right. But I JB welded it because it couldn't hurt and I didn't want to come back to this crack.

Based on everything else in this thread, do you have any suggestions for me?
 
Pull bypass covers and inspect pistons / rings.----Flywheel key checked ?----Yes it very well could be an issue with crankshaft sealing rings.
 
Just an update. I did the JB weld and put my carbs back on.

Both of my outboards are plumbed to one water separator. My main uses VRO, and my kicker has an Accumix in it's side of the fuel system. I figured out that there are no anti-siphon valves, so it's plausible that my main engine is pulling oil out of the accumix. So I installed a shutoff valve on the kicker side of the water seperator.

Still had idle problems the next day on the water. I took my IR gun with me to check head temps but it had a dead battery :/

The flywheel key is there. I haven't pulled the bypass covers.

I bought a DVI adapter and I'm going to do ignition checks before I pull bypass covers. I am thinking that I might have an electrical component that is good when cold, and has problems when warm. So I'm going to warm my engine up and run through the CDI troubleshooting guide. Then I'll check my head temps too. If that all tests fine, I will pull the bypass covers for visual inspection, and probably replace my crankshaft seals too.
 
After running on plane for a while I stopped to check head temperatures. Both were about 135 read with an IR gun.

When I got home I was getting ready to do thermostats and noticed this brown sludge. Only on the Port side. Which again makes me think lower crankshaft seal. I took the flywheel off and did a visual inspection of the upper crankshaft seal and it looked okay to me.

Back to the sludge, I cannot find wetness on the head gasket or the thermostat housing. It could possibly be water mixing with a leak from the fuel or oil line. Not sure. But the way it is spread over the entire left side makes me think it is a crankshaft seal.

I also have a rattling noise that gets worse with RPM. Thinking it was my lower unit oil, I changed it. No change in rattle. Maybe a bad lower crank bearing.

IMG-20210620-142707.jpg


 
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