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The cycle of 93 Johnson 90hp piston

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fishhawk90

Member
Hey guys I was just wondering if anyone knew the firing order of the piston for a 93 johnson 90hp. Its an VRO engine with 4 cylinders 2 on each side. I know that the crankcase is split in two half & just wanted to understand how the vacuum to the fuel pump is drawn. thanks
 
Facts----- there are 4 separate crankcases .-----The fuel pump runs on a POSITIVE pressure pulse and a slight negative pressure pulse.------Pulses below the piston are caused by piston moving up and down in the cylinder.
 
So the pump is activated by pressure/vacuum pulses created by the piston on the given chamber that is tapped into for the pump. The VRO has a rubber composition diaphragm which when exposed to ethanol, will break it down. Never use ethanol in an outboard such as yours. Stabil will prolong the life of petrol/ethanol blend, but it can't remove the ethanol. The crankshaft seals can also be damaged. Manufacturers have modified seals over the years, using viton and other materials, but ethanol will eventually destroy those too. Replacement VRO's are labeled "alcohol resistant"......I have seen those fail too, destroying the oil injection system, causing cylinder scoring and motor destruction. Let me know if you want any photos of buckets of destroyed VRO motors.
 
The VRO or any fuel pump is operated by crankcase pressure created by the downward action of the piston... in your case, the VRO being controlled by #4 piston I believe. The diaphragms in either case are spring loaded to return to their original position... aided by a mild vacuum supposedly. The vacuum created isn't enough to affect the diaphragms otherwise.

I assume you know, but just in case..... standing in back of the engine and facing the spark plugs, the cylinders on a V4 are numbered as follows.

2.....1
4.....3
 
timguy said:
So the pump is activated by pressure/vacuum pulses created by the piston on the given chamber that is tapped into for the pump. The VRO has a rubber composition diaphragm which when exposed to ethanol, will break it down. Never use ethanol in an outboard such as yours. Stabil will prolong the life of petrol/ethanol blend, but it can't remove the ethanol. The crankshaft seals can also be damaged. Manufacturers have modified seals over the years, using viton and other materials, but ethanol will eventually destroy those too. Replacement VRO's are labeled "alcohol resistant"......I have seen those fail too, destroying the oil injection system, causing cylinder scoring and motor destruction. Let me know if you want any photos of buckets of destroyed VRO motors.
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I would like to see those pics. I.would also like to see pics of the internals of these failed pumps.
 
thank you all for the response. Now that it's clear each cylinder has it's own case which one will be the culprit for a leak @ the top crankshaft seal? & is it possible to change this seal without tearing the all motor apart. thanks
 
??----What is your motor doing / not doing ?----The top crankshaft seal rarely fails.------Has any trouble shooting been done or is there some guess work done here ?
 
The main cause of death of these seals is ethanol, perhaps Mr.Scott would like to see some pictures of the seals too. It is much more likely that "fishhawk's" motor has had the VRO replaced once already before the seal will fail. In other words, you will likely notice an "alcohol resistant" tag on that replacement VRO. Also you may notice some leakage from the seal area as the crankcase produces pressure when pushing in the fuel/air charge, then a vacuum atmosphere as it enters compression or firing situation. So the seal will leak as well as suck. As my science teacher pointed out, the pressure created in the crankcase is more than.....or over and above the vacuum created because the reed or rotary valves will yield to the vacuum, thereby reducing its intensity as the crankcase "sucks in" the fuel/air mixture, as the VRO determines the correct amount of oil to inject......more for high speeds and less for low speed and idle........and sometimes "NO" oil after ethanol damages the VRO.
 
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Sorry, Racer, I was making edits to adjust my post.....yes these particular seals rarely fail because other issues will surface first. The top cylinder will indicate a leaner burn.....fishhawk needs to compare plug color.....then you might see a "red flag" on that possible seal failure.
 
Tim u r a genius & dead on abt the mixture on the top cylinder being lean because when i bypass the primer it runs but them stalls in gear. also the previous owner did use 87 fuel with 10% ethanol.
 
No, not a genius.....far from, but some other causes too could produce a lean burn. Is there any oil around the top seal area?
 
Ethanol......E85.......for example, delivers a 25 to 35 percent decrease in performance/fuel economy, when compared to pure petrol gasoline.......so the price savings don't even make up for the added fuel burned. Don't get me wrong, Fishhawk, I LOVE ethanol, the damage it causes to marine and seasonal equipment, gives me a large part of my repair business. But once I repair the unit for my customers, I educate them so they don't make the mistake again. "Once bit......twice shy, brother".
 
their is no oil Tim did the test with premix on top while rotating the crank & saw bubbles, also took the vac hose off to the vro & got very weak vacuum. if the vro is controlled by piston #4 bottom left why is the leak @ the top effecting it?
 
The " leak " on the top cylinder does NOT affect the VRO machine !!!------The reed valves OPEN so you do not see a vacuum at the VRO port !!!-----What other trouble shooting has been done ?-----Post the results of a compression test first.
 
So let me get this straight when you bypass the primer the motor does not.run right. Sounds like you have 2 problems a leaky primer and a plugged carb. The primer works off of the fuel pump and is just a valve that lets fuel through. If it leaks it in effect replaces the carb, and if that is the case you have a dirty carb. What are the results fo the compression and spark test. Ethanol has been around in fuel for over 40 yrs it is time to stop blaming all the 2 strk problems on it. The same goes for Vro pumps.
 
I'm not blaming ALL, the worlds problems on ethanol, brother. But our viewers and readers may thank me someday. Ethanol has been almost "forced down" our throats for some 25 years now. Its fine for you, but not for me and my customers. I have several collector cars and trucks......they will NEVER TASTE ETHANOL.....EVER!!!! I WORKED TOO HARD TO BUILD THEM. Let the readers make their own choice......I'm just trying to help them from agrivation, grief, and expense. I've given advice from the heart to save this older equipment and put smiles on the faces of the operators. You are a great man, and I thank you for all you do here on the forum.....no hard feelings on my part, brother.
 
timguy said:
I'm not blaming ALL, the worlds problems on ethanol, brother. But our viewers and readers may thank me someday. Ethanol has been almost "forced down" our throats for some 25 years now. Its fine for you, but not for me and my customers. I have several collector cars and trucks......they will NEVER TASTE ETHANOL.....EVER!!!! I WORKED TOO HARD TO BUILD THEM. Let the readers make their own choice......I'm just trying to help them from agrivation, grief, and expense. I've given advice from the heart to save this older equipment and put smiles on the faces of the operators. You are a great man, and I thank you for all you do here on the forum.....no hard feelings on my part, brother.
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You can holler all you want but millions of plastic car fuel pumps are submerged in E10 for hundreds of thousands of miles and no problems. The same goes for the rubber O-ring/gasket that seals them to the tank. Plastic gas tanks seem to survive all right. Rubber car filler hoses hundreds of thousands of miles with no replacement. Sorry the ethanol problem no longer holds water as a major problem with outboards. But i guess it is easy to blame ethanol than to tell somebody Hey your fuel pump is old and needs to be replaced.
 
Mr. Scott. Don't listen to me. Just do this one thing for me before you continue your rampage. Open Google Search and type in "what does ethanol do to rubber"? Read up on a few sites.....including the EPA site. I have one question for you then. Why do you want to argue with someone who is RIGHT?
 
did a compression test pretty even number across all cylinders 100-110. I also pinched off the 1/4 fuel lines to both cab & tried to start with only primer line & it didn't which tells me cabs r working fine. Spoke to a marine mechanic as said the issue lines in the crankcase seals & gasket & it's a complete tear down & replacement. will keep u guys posted as i strip it down.
 
Fishhawk..... Your very first question (Post #1) pertained to the V4 firing order or which I and apparently many others somehow skipped over.

That would be simply 1, 2, 3, 4 .
 
Wait a minute, brother. You can replace upper seal without a complete teardown, the seals between the crankcase chambers are probably fine. The lower crank seal may be okay too. What exactly are the symptoms, Fishhawk?
Mr. Scott, I feel bad that I snapped at you, I am very sorry. Forgive me please.
 
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Tim i dont want to take any chances. I dont know why Johnson made a motor without any gasket between the crank & block so am going to loctite everything to be on the safe side.
 
No don't do that, there is no gasket between crank and block ......talking about crankshaft bearings, but there are o rings. These simply rarely fail. The block sections use loctite/gasket eliminator, but that too rarely fails.
 
Fishhawk----------That block and crankcase cover is a metal to metal joint.---No gasket.--------Perhaps you are working on your first motor and making assumptions !-----Work per a manual.----Work carefully !
 
fishhawk90 said:
Tim i dont want to take any chances. I dont know why Johnson made a motor without any gasket between the crank & block so am going to loctite everything to be on the safe side.
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Between the crank (crankshaft) & block?...... I have no idea what that means...... Are you speaking about the lack of a gasket between the two crankcase halves? If so, that incorporates a substance that cures/seals with the "lack" of air, as follows:

********************
(GelSeal & LocTite 518)
(J.Reeves)

GelSeal and the equivalent substance of LocTite 518 creates a sealing condition due to the absence of air. What remains of the substance after torquing the retaining bolts, as you may have noticed during disassembly, is a very thin almost clear sheet of sealant.

There is a removing substance to remove that old sheet but I have found that it can also be removed by carefully using a sharp putty knife like tool. Just be careful not to actually scrape into the aluminum surface.

There are various methods to applying this sealer. My method is to apply a thin bead of the sealant from one end of the crankcase to the other, then spreading it around with ones finger so that it encompasses all of the bolt holes.

Make sure that you do not apply that substance any closer than 1/4" to the Main Bearing areas or to the Taper Pin holes.

As mentioned above, the substance seals with the absence of air, meaning that as soon as you set the other half of the crankcase in place, the substance starts to slowly take effect. So plan your job so that once you start this portion of the rebuild, you follow straight thru to the finish (all bolts tight and torqued).

The sealer substance that squeezes out internally will not harden as it will still be exposed to air. This will simply blow out the exhaust as the engine runs. The excess that squeezes out externally.... simply scrape/wipe it off to eliminate the gooey appearance.

********************

Stick a gasket in there and I guarantee you'll be doing double work at a great added expense within a very short time.
 
Joe, great advice. Remember the old sealant we used in the 60's? Loved that stuff, I actually think it is every bit as good as this newer orange Loctite 504. I have also used the 518 which seems to do the job too, although the 504 is used more widely by me. It has a little "grit" type substance that when squished seems to help expedite its hardening. Has anyone out there tried the 504? I understand that the 504 is still an anaerobic but this "grit" substance is an additional activator when it is compressed. Not sure how much truth is in that theory, I never spoke directly with Loctite on this particular product. When I overhaul an outboard I give a full 1 year warranty, covering parts and labor, I should probably make more certain that 504 is better in this application (case halves), than 518. My history, since using 504, 2004 to present is still 100 percent. I just don't answer the phone if I see its an old customer........hah! Only kidding.
 
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You do not want any " filler " in the sealant !!!------Most , if not all the sealant has to squeeze out of this joint.-----This ensures proper " clamping " of the center bearing and the upper and lower bearing housings.-----This is precision , simple and fine machinery.-------Use factory gel seal or Loctite 518 on this.
 
Not sure that I would call it a "filler", because the film thickness seems the same as the red stuff (518). I have had no comebacks yet on it. I have used it since about 2004. I know that it is more expensive than most anaerobic compounds suitable for what we are talking about, but only now I will Google up the price difference of the 2 products. Maybe I will see what they say on applications as well. Are you old enough to remember that OMC yellow/brown product? I really liked it. Used it on other gaskets too, like lower unit case halves in conjunction with the spaghetti seals. Maybe its still available.
 
Okay looks like 518 fills gaps to 50 thousanths with primer and 504 goes to 30 thousanths gap. They didn't say what the filling properties are of 518 when used straight from the tube, so we can assume it is something less than .050. Both these numbers of course are insane because I would expect 3 to 5 thousanths max. I think its a typo....gotta be.
 
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