most frustrating V4 omc issue ive ever experienced

[JoshKeller]

background - the motor is a 1994 90/65 johnson jet. 90 powerhead. has run great since i got it. This morning we were running up the river and it lost power. went from 5300 rpm down to 4300 rpm. shut her down and floated back to the ramp. determined it was the upper port side cylinder that was the culprit. with a jet i can get full rpm on the trailer - with the top port cylinder wire unhooked it still turns 4300 and has no effect if hooking up the wire. Other cylinders drop it down to 3200 rpm. It WILL make a difference at idle when pulling the plug wire off. with the silencer off, I can clearly see fuel spraying out of all 4 carb tubes at WOT. Spraying fuel/oil mix into the carb while running WOT makes me change.

I have a spare powerhead, so I have access to a lot of parts. I started by running a compression test -

121, 120, 115, 118 - so that appears good.

New plugs - with 20 minutes of testing/run time 3 are showing burned fuel signs the top port is clean.

powerpack, coil, plug wire, stator, timer base - none made a difference.

another carburetor - no difference.

pulled reed cage/intake to verify everything was good, no block cracks, etc - no issues.

Pulled port side head to visually inspect - top cylinder was clean as was the head - thought perhaps a water leaking issue. Put on spare head with new gasket - still have the same issue.

Im at an absolute loss. What else could it possibly be? Am I overlooking something? The only electrical part on the motor i havent replaced is the flywheel itself - However, i am getting spark at all throttle levels. Im thinking this has to be some sort of weird fuel issue?

[PanRonnie]

i think you need a voodoo priest!!! :eek:

[flabum1017]

Swap plugs around? I have seen brand new plugs take a dump.....................

[hq_]

One of the flywheel magnets cracked?

[bullet123]

Swap plugs around? I have seen brand new plugs take a dump.....................

What he said :iagree:

[JoshKeller]

What he said :iagree:

I have tried 2 sets of new plugs thus far.

[bullet123]

Clean cylinder is usually a sign of no spark or water intrusion. Im not an omc guy. Is there anything on those engines besides the coils that can be isolated to one cylinder? Maybe flywheel like hq_ stated above?

[PanRonnie]

As you say it is having fuel and spark��
Did you test this with a hot or a cold engine?
If it has quick start during cold the spark routing is different
Can,t remember if the coolant wire is grounded during cold or open will have to check

[flabum1017]

Possible water leak in the exhaust spraying water into the exhaust port on that cylinder, That's a cross flow v-4, right?

[flabum1017]

You can also index each cylinder on the flywheel and make sure they are all firing where they are supposed to.

[FMP]

Pull the plug with wire and spin it , spark? What rpm does it break down? Bad wire somewhere?

[racervboat]

bad coil,cranking has spark yes? running has no spark? with it running pull plug wire and hold it to the plug and listen for the spark tick tick tick get it?

[FMP]

Coil is on a remote controlled switch by Tohatsu

[racervboat]

what the hell does that mean? you turning japanease I really think so. lol

[FMP]

Lol

[racervboat]

:iagree::cheers:

[PanRonnie]

If you have the wire why not measure the voltage side of the coil ?

[JoshKeller]

update - its not the flywheel. Put it all back together, took it down to the river and tested it on the trailer. It ran strong for a few seconds, then dropped the cylinder again and then sputtered a bit at idle - removed the plug wire off top port cylinder and no change. Removed the spare head, and there was a drop of water in the head and it too was cleaned off after about 8 - 10 minutes of runing. Im thinking maybe the new gasket i got was bad. It ran strong until water circulated and breached the gasket, then as water entered the cylinder, it stopped firing and began cleaning itself out.

https://imgur.com/gallery/NS4Ui

[flabum1017]

Post # 9 maybe?

[JoshKeller]

Possible water leak in the exhaust spraying water into the exhaust port on that cylinder, That's a cross flow v-4, right?


Sorry, I missed this - how would I determine if this was the problem? It is a v4 cross flow.

I have determined with 100% certainty, i am getting spark at all rpms.

[flabum1017]

383299


Just pull the exhaust chest off (both plates), Slots in the middle are the water cavities

[flabum1017]

Also, take a close look at the inner plate (49) for holes; the space between the inner and outer plates (51) is a water cavity also.

383300

[JoshKeller]

will give it a shot after I replace the head gasket again. If that doesnt solve the problem, im looking at just throwing my spare block on and going with it. Upon closer inspection, I can see where water was leaking from the gasket, and one of the bolts was stripped, but being held in by corrosion - directly across from the plug hole on the problem cylinder. i drilled and tapped to 3/8", so i will give this a shot first.

[mn808gade]

post#9

[JoshKeller]

If it turns out to be #9, what is the best repair?

[flabum1017]

Make sure the surfaces are level and new gaskets.

[JoshKeller]

Alright pulled the exhaust covers off, but unable to tell if the gaskets were bad, as i had to pry it off. The top cylinder seems cleaner. There is DEFINITELY water entering that top cylinder from somewhere. Any other places it can come in? I ordered new exhaust gaskets.



https://imgur.com/gallery/qSMHo

[mn808gade]

got sum cleanin and tappin to do.little hint--press 1/4x20 nut over square end of tap and use a socket on end of tap..-th

[flabum1017]

How does the inner exhaust plate look? Any holes or cracks in the vicinity of the wet cylinder?

[JoshKeller]

How does the inner exhaust plate look? Any holes or cracks in the vicinity of the wet cylinder?

No, appears to be good. Water has to be coming from somewhere though

[JoshKeller]

Update - new exhaust gaskets, same issue. Pulled off the plates on my spare motor will test tomorrow. In the tank, it runs on all 4 cylinders up to 2500 rpm. Im going to put clear tubing from the vro to the vacuum to see if maybe its pulling fuel from the vro and flooding out. After running 30 minutes in the tank at 2500 rpm, the plug has fuel burned on it, and isnt cleaned off. It ran great until you hit wot, then it bogged down and quit running on the top cyl until the water cleared out (15 seconds). Are there any places water can enter on the intake side? Im really at a loss here.

[perfmarine1]

I have see V4's leak water right through the block and cylinder ,a pit hole. Now you would not think this could happen since the sleeves are dovetailed in when cast, but it does happen. Hook a hose to the water tube, gearcase off of course, and look in spark plug hole with camera and see if you have a water leak.

[JoshKeller]

Only problem is, it ONLY starts at wot. I ran it for 30 minutes in the barrel and it ran perfect.


I have see V4's leak water right through the block and cylinder ,a pit hole. Now you would not think this could happen since the sleeves are dovetailed in when cast, but it does happen. Hook a hose to the water tube, gearcase off of course, and look in spark plug hole with camera and see if you have a water leak.

[flabum1017]

Only problem is, it ONLY starts at wot. I ran it for 30 minutes in the barrel and it ran perfect.

More heat builds up at WOT, probably opening a crack in the sleeve and block. Or as Perfmarine says, allowing water to get through between the bloc and sleeve. Might need to pull the head, clean the aluminum casting around that cylinder real well and check for cracks. You have eliminated everything else.

[flabum1017]

Could also be in the head NEVER MIND! saw you changed the head already

[JoshKeller]

At this point, im wondering if its not best to just scrap tbis block and find another. These v4s are pretty cheap, and its incredibly frustrating not being able to duplicate the symptoms in the tank or on the bench.

In the event i find a leak in the block or sleeve, how would i go about repairing it?

[JoshKeller]

I have see V4's leak water right through the block and cylinder ,a pit hole. Now you would not think this could happen since the sleeves are dovetailed in when cast, but it does happen. Hook a hose to the water tube, gearcase off of course, and look in spark plug hole with camera and see if you have a water leak.

Tried sending pm, but your inbox is full

[perfmarine1]

Should have room now,thanks.

[FMP]

Reminds me of a SB Chev I had. Great motor, all the right parts, would only eat coolant on a long highway run. Never in the oil, not the heads, not the gaskets, wouldn't leak down pressure testing cooling system. Cracked across back two cyl on one bank. Would steam into valley and pcv would eat it . Slow down off the highway and nothing. Idle perfect, ran without a miss. Threw the 4 bolt block in the trash and went high nickel.

[JoshKeller]

Ive given up on this block. I have another motor needing put together (also a 1994 90), that i had bored over .030 and never bothered assembling due to having a running powerhead. My buddy offered me a 1984 90 hp, would it give similar power to the prop rated 90? And would i be able to swap the exhaust covers to be able to mount my trim relays?

Drives me nuts that i cant find the leak, but with other options easily at hand, ive sunk enough time and money in it.

[flabum1017]

'84 90 is prop rated 90............. everything will bolt up, everything can easily be swapped.

[FMP]

Swap it , just don't go nuts if does the same thing... kidding

[JoshKeller]

Local marina has a 1992 115hp counter rotating for sale. Counter rotating is simply in the gear case right? Since id only need the powerhead, is there a ysed market for the mid section, trim, counter lower?

[DanUmbarger]

Just swap gearcases and go boating!!!



Local marina has a 1992 115hp counter rotating for sale. Counter rotating is simply in the gear case right? Since id only need the powerhead, is there a ysed market for the mid section, trim, counter lower?

[flabum1017]

They didn't make a counter rotation v-4 crossflow in 92, in fact I don't think they ever made a v-4 crossflow counter rotation. Maybe someone put a looper gearcase on that

[FMP]

Why not just run a gear case? Running a rocky river?

[JoshKeller]

Why not just run a gear case? Running a rocky river?

Yes, the Potomac and susqhuehanna rivers. My boat is a custom built 17' 60" bottom stick steer with 1/8" sides and 3/16" bottom.

[JoshKeller]

Ok, just a thought. I pulled the powerhead and the base gasket was destroyed. Mostly gone. Would this cause this issue? Possibly water under wot pressure going up into the exhaust chamber, hitting deflector on the exhuast plate, and going into the cylinder?

[FORBESAUTO]

Very possible, if water shoots across ports at plate it will kill upper rpm. It makes backpressure and messes with all the exhaust tuning. And if makes its way into a cylinder kills it even more. Need to run a straight edge over plate and sure it's flat also. I've had problems with this on a 2 piece mercury plate and would loose 400 rpm and also found had to idle it up some to maintain idle in gear. Took me a while t figure out what was happening.

[FMP]

Run gas instead of water as coolant and see what happens?:eek:lol

[JoshKeller]

Sadly, im so frustrated at the point, i was going to remove the water pump and see if it would hit wot rpm to verify it was an issue with high pressure water.

[flabum1017]

Ok, just a thought. I pulled the powerhead and the base gasket was destroyed. Mostly gone. Would this cause this issue? Possibly water under wot pressure going up into the exhaust chamber, hitting deflector on the exhuast plate, and going into the cylinder?

I would think it would hit the bottom cylinder first, but strange things happen with these engines at times. Replace the gasket and be sure the surfaces are level.

[JoshKeller]

Another crazy update. Threw together my other powerhead. Different blocks, electronics, etc. Mounted it on the mid section, ran it a bit in the tank - ran good. Took it to the river and same thing. Nothing after wot. Water getting into top left cylinder. I dont believe this issue is a powerhead issue at this point.

[FMP]

Exorcism

[flabum1017]

Another crazy update. Threw together my other powerhead. Different blocks, electronics, etc. Mounted it on the mid section, ran it a bit in the tank - ran good. Took it to the river and same thing. Nothing after wot. Water getting into top left cylinder. I dont believe this issue is a powerhead issue at this point.

Water spraying into the carb?

https://www.youtube.com/watch?v=sV3ZoYscXVM

[JoshKeller]

Water spraying into the carb?


dont believe so. it still ran good on the other 3 cylinders. ran great until i hit WOT then the top cylinder died off. Its definitely getting water in the top cylinder from somewhere, even with two different powerheads. I took off the lower, used the water hose let it run for about 5 minutes. pulled the head, and there was now was in BOTH left cylinders, but much more in the top. drops in the exhaust ports as well. it makes no sense to me either how its effecting the top cylinder, but not the bottom since the water would have to pass right by the bottom cylinder.

[flabum1017]

Any signs of water outside the powerhead? Thermostat housing and hoses good? Pisser hose good? Try running it without the cover?

[FMP]

This ain't real man, driver stop the bus. You running the same carbs on both? Leave it outside with the cowl off during tomorrow's solar eclipse.

[JoshKeller]

Two different sets of carbs. Different flywheel, coils, powerpack, trigger, stator. There is wster coming from between the powerhead and mid section now. Nothing from the heads, pisser, thermo hoses. There may have been before, i never checked. Motor has been run without the cowling to eliminate spark jump, ghost encounters, anything else i could visually see.. Motor has been run on the trailer and off. The fact that its doing this with two powerheads definitely makes me believe that perhaps the powerhead gasket is to blame, just seems odd its only on the top cylinder getting washed clean on both blocks.

[FMP]

If that's where you think it's coming in and getting into the lower chest, it's someway getting caught in a pulse and making it as stuffing. One side, top only makes wonder how it's not getting in the lower with its stuff. Must be just how things are pulsing.
Swapping P/h without new gasket?

[JoshKeller]

I swapped the powerhead simply to see if the problem stayed with the block (like i assumed it would), or followed to this new block. Really had nothing else going on today, so I figured I'd mess around in the ac'd garage and get everything wired up, ready to go so I can just use the motor hoist to lift the powerhead 6 inches and then put the gasket on and hopefully go with it. I ordered a new gasket and will be installing it when it arrives.

I'm not 100% convinced this is where its coming in from, but where else can it be? Ive tried two blocks, different carbs, different exhaust plates, different heads and gaskets, different spark plugs and wires, coils, powerpacks. On trailer, off trailer. Trimmed up, trimmed down. Seems like the only thing I havent gone over is from the base of the powerhead and down.


If that's where you think it's coming in and getting into the lower chest, it's someway getting caught in a pulse and making it as stuffing. One side, top only makes wonder how it's not getting in the lower with its stuff. Must be just how things are pulsing.
Swapping P/h without new gasket?

[FMP]

Post 13

[JoshKeller]

Post 13

I'm not sure what you mean by coil is on a remote controlled switch by tohatsu? its firing at all RPM.

[FMP]

Just hoping you plug the leak

[JoshKeller]

Just hoping you plug the leak

im lost?

[mn808gade]

in '79 had a 235E on switzer,every time 80+ it would fall on its face,by time i idled down to ck plugs,could not find problem.did a full speed throttle chop/plug check and found one plug with water on it,exh gasket was letting water pass into exh stream and that cylinder would cut out-th

[PanRonnie]

remove frustrating omc v4 from boat
install mercury v6

[Mark Poole ModVP]

There are so many stories of OMC motors.....the last 5 or 6 years they were made...crazy problems. Most of it was the fact that the machining equipment was so out of tolerance that nothing was being made right. My dad has a '95 model 90 that is a POS compared to the '79 85 that it replaced.

[JoshKeller]

remove frustrating omc v4 from boat
install mercury v6

Not an option. I need a jet pump and not paying 2 grand for another one.

[JoshKeller]

in '79 had a 235E on switzer,every time 80+ it would fall on its face,by time i idled down to ck plugs,could not find problem.did a full speed throttle chop/plug check and found one plug with water on it,exh gasket was letting water pass into exh stream and that cylinder would cut out-th

I replaced both exhaust gaskets on both powerheads.

[FMP]

If you take the lower off and attach a hose to the water tube and feed it fresh water does it drop a cyl? Probably wouldn't develop enough heat without load to show. Warped ex plate base plate ?
Those jets, do they use a regular stand alone water pump or jet pressure?

[JoshKeller]

If you take the lower off and attach a hose to the water tube and feed it fresh water does it drop a cyl? Probably wouldn't develop enough heat without load to show. Warped ex plate base plate ?
Those jets, do they use a regular stand alone water pump or jet pressure?

I will try that test this evening when i have help. I believe the motor will race without the drive shaft hooked up, so i want someone to be able to kill the motor asap.

Ive tried two different exhaust plates/gaskets/covers.

The jet uses a standard water pump on the driveshaft which is fed by the jet impeller.

[FORBESAUTO]

Did you straight edge the base plate? Technically the base gasket shouldn't blow if has even clamping pressure across all of the gasket. They usually blow out due to a low spot in plate or loose ph mounting studs. If your gasket was severely blown, chances are your problem is in that area.

[FORBESAUTO]

When you hook water supply to the tube, you can look up through mid and into tuner and see if you have any water entering into exhaust ports.

[FMP]

Some luck, two motors eating water. Could an over pressure happen at speed to blow out these gaskets? The jet feed to the water pump, any orifice adjust or like that may have been lost?

[JoshKeller]

Some luck, two motors eating water. Could an over pressure happen at speed to blow out these gaskets? The jet feed to the water pump, any orifice adjust or like that may have been lost?

Not that i know of. Theres literally hundreds of these motors running around here. This one ran perfect for 8 months then all of a sudden started getting water into the cylinder

[JoshKeller]

Alright, I feel like maybe I have been chasing a phantom issue. I finally had help today looking at the motor, and I was able to sit by the motor while it was running and messing with the throttle speed vs cylinder drop. It runs absolutely perfect at ALL rpm, until the high speed jet kicks in. Once fuel starts coming up the volute tube, the cylinder is completely dead. Drop it just enough rpm until the fuel comes out of the other jets, it runs perfect. This is with two different carburetors. Reeds LOOKED ok, but im not too sure what else it can be. The VRO pump appears to feed off the bottom cylinder's reed cage, so I dont see it being that. Will too much fuel wash the cylinder and exhaust ports clean just like water? After carefully removing the head today after running, I believe most of the water I saw in the cylinder and exhaust port was from removing the head itself.

[flabum1017]

Doing the same thing with two completely different powerheads, carbs sets, ignition etc...... do you have an electric fuel pump in the boat that might be putting too much fuel pressure? Are the exhaust cavities clean in the mid and lower? Any rattling noise in the mid? Take the primer hose off the top carb and pump the primer bulb nice and hard and see if there is any fuel coming out of the primer hose (cracked primer solenoid cover)

[flabum1017]

did you try squeezing the primer bulb when you lose that cylinder?

[JoshKeller]

I dont have an electric fuel pump. Just had the mid and lower apart and flushed everything with water. no rattles or anything. The cylinder definitely cuts out the second the fuel starts shooting up the volute tube. Ill go check the primer now.



Doing the same thing with two completely different powerheads, carbs sets, ignition etc...... do you have an electric fuel pump in the boat that might be putting too much fuel pressure? Are the exhaust cavities clean in the mid and lower? Any rattling noise in the mid? Take the primer hose off the top carb and pump the primer bulb nice and hard and see if there is any fuel coming out of the primer hose (cracked primer solenoid cover)

[JoshKeller]

did you try squeezing the primer bulb when you lose that cylinder?

I did, i even pinched off the vaccuum hose with hemostats.

[JoshKeller]

no fuel coming from primer solenoid when pumping bulb.

[flabum1017]

If it were just one carb and not two doing it, I would say check to make sure the high speed jet didn't fall out.

You did say two completely different powerheads are doing the same ting?

[JoshKeller]

yes sir, two powerhead. I will say, that I did reuse the intake manifold on both powerheads, with a new gasket. I have flipped carbs back and forth with no success

[flabum1017]

might want to take another look at the reeds, maybe swap the reed box on that cylinder with another cylinder and see if it follows. A loose reed box can cause problems too

[FMP]

Time to sit down on a stump and scratch something

[JoshKeller]

Believe I have it solved. What are the odds that BOTH sets of carburetors have the high speed jet missing on the port side top carburetor? 100% in my case. Should I possibly blue lok tite the new ones in? call it a fluke and just get a spare or two?

[flabum1017]

Believe I have it solved. What are the odds that BOTH sets of carburetors have the high speed jet missing on the port side top carburetor? 100% in my case. Should I possibly blue lok tite the new ones in? call it a fluke and just get a spare or two?

Holy crap! Just get them in good and snug. I don't know how well locTite will do submerged in gasoline

[FMP]

Thought you checked carbs way back. Guess not

[DanUmbarger]

I thought you had said the motor was running fine then all of a sudden lost power...doesn't make sense that the motor would run good with a high speed jet missing. Hope this is the problem.

[phillnjack]

this is a frustrating thread never mind the v4 ha ha

been racking my brains out then he says its got no main jets ? wtf..

[FMP]

In both carbs

[JoshKeller]

I thought you had said the motor was running fine then all of a sudden lost power...doesn't make sense that the motor would run good with a high speed jet missing. Hope this is the problem.

This was the problem. I have absolutely no idea where the jet went. Ive run this notor for 8 months and know for 100% certainty it had the jet - i remember spraying it out and cleaning it with wire. Open up the bowls on both sets of carvs, and both are missing the same jet

[flabum1017]

Yeah, that's weird about the jet. I had a motor come in years ago that leaned out a cylinder. The main jet had backed out and wedged creating a blockage.... could go one way or the other............. be happy it was rich and not lean. Strange you could not find the jet, did you pull the bowl off? Maybe it was in the cowling and fell on the floor when you pulled it apart............ not something you would have been watching for

[FMP]

It's magic

[JoshKeller]

Yeah, that's weird about the jet. I had a motor come in years ago that leaned out a cylinder. The main jet had backed out and wedged creating a blockage.... could go one way or the other............. be happy it was rich and not lean. Strange you could not find the jet, did you pull the bowl off? Maybe it was in the cowling and fell on the floor when you pulled it apart............ not something you would have been watching for

Never did find the jet - in either carb. I have ordered a spare and will keep it in my tool box on the boat. Possible it fell on the floor, i wouldnt have been searching for it at all. All i know now is that i have 2 good running 90 blocks, and im debating if its worth it or not to get a 115.