2000 Johnson 90hp. PLEASE Help. Very detailed description of problems

[kboater]

This is a very long post, i have tried to be as detailed as possible. PLEASE read it and give me your opinion….Please

I recently purchased a 2000 key largo with a 2000 90hp Johnson Ocean Pro on it. (with VRO)
The seller was upfront with me that at low idle (when throttling down) sometimes it would die, but it would always fire right back up. I sea trailed the boat and it did exactly as the seller described. After, I had a reputable mechanic come check out the motor before I actually purchased it. The mechanic did a compression test and all 4 cylinders were over 100psi and all even. he found no other problems, but he could not repeat the dying at idle on muffs (as it only did it on the water). He said it was probably a warped float bowl chamber and would be a fairly easy fix.

I feel like he is a good mechanic, been doing this for 30 years, familiar with this motor, and he is not just a parts changer.

Well, it turns out that a few of the float bowls were warped, but not causing the issue. he found out that On number 4 cylinder the spark plug was getting wet with water, which is why he thought it was dying and not sucking the fuel properly. He tore about all 4 carbs and adjusted float bowls and found nothing wrong. So then he pulled off the heads and noticed that the head gasket o rings were not in good shape, there was some rtv sealant plugging some of the water openings, and the heads were not in great shape. So he thought that water was leaking from the water jackets (i think thats what they are called under the heads) so he had the heads machined so they were in good shape and nice and flat again. then he put new head gasket o rings on and it was a little better, but cylinder 4 was still not pulling fuel at low idle and the plug in that cylinder was still wet with water. all 3 cylinders, except number 4, actually picked up about 10 psi of compression after doing the heads. number 4 had stayed about the same. So now he thought the rings on the piston in cylinder 4 were stuck which was causing cylinder 4 not to pull enough fuel at idle, but also let a little moisture from the exhaust port, inside the cylinder, be pulled into the intake port which was causing the wet plug. So he did some ring free and let it soak. Well that freed up the ring and now that cylinder has the same compression as the other cylinders, but the plug in that cylinder 4 is still wet causing it to die at idle. He said when he manually chokes cal 4 it picks up as it is pulling more fuel and the spark plug start firing again……

so, that is where we are at now. He has fully checked out the VRO, fuel and oil are both 100% free from water, and carbs are 100% he says. he said there are only 2 other places that water could be coming into cylinder 4 causing the plug to get wet which is causing it to die at low idle. He said 1 place could be block rot, but be is 99% sure this is not the case as he has found no evidence of it and he says that these motors were not at all prone to it. The only other place he thinks water may be coming in is from the lower main seal. I think he said that is near the crank….

I think he is a very good mechanic, not just a parts changer, and he really wants to fix this as we are both frustrated at this because it seemed like a simple problem at first and now we are about to tear down the motor to get to the lower main seal as that is where he thinks the water is coming in, causing the plug to get wet, and causing 4 cylinder to die at low idle….

does this sound like we are on the right track? we both think we have tried the simple, cheapest things first, now we are left with this lower main seal….Can someone chime in and let me know if you think we are on the right track? Any suggestions?

EDIT Edit: just spoke to the mech, and to clarify about the lower main seal he said:
The power head base gasket is the mounting surface and the lower main is the sealing surface between the bottom cylinder and the water in the exhaust. the base gasket and the lower main seal are the two that will be replaced, you cant pull the power head and reinstall without a new base gasket you can however pull the power head and reinstall without replacing the lower main seal. we will of course be replacing them both

 

[fireman57]

Not real familiar with this engine but on most water can only get in from a bad head gasket or exhaust gasket. Two totally different areas. Since he has gone through the heads and freed the piston I would pull the exhaust side and replace those gaskets. Can't tell you how many engines I have done this on. Okay, I will tell you, 5. If he knows you are getting water in the cylinders a carb rebuild won't solve it.

 

[Chris1956]

Does your mechanic know to put some RTV Silicone around each water jacket passage on the block, before installing the head? If not, that could be the source of the water.

 

[kboater]

Not real familiar with this engine but on most water can only get in from a bad head gasket or exhaust gasket. Two totally different areas. Since he has gone through the heads and freed the piston I would pull the exhaust side and replace those gaskets. Can't tell you how many engines I have done this on. Okay, I will tell you, 5. If he knows you are getting water in the cylinders a carb rebuild won't solve it.

I will pass this along to the mechanic. Thanks

 

[kboater]

Does your mechanic know to put some RTV Silicone around each water jacket passage on the block, before installing the head? If not, that could be the source of the water.

I would assume that being an experienced mechanic, he would know this. But I'll pass it along just incase

 

[daselbee]

Does your mechanic know to put some RTV Silicone around each water jacket passage on the block, before installing the head? If not, that could be the source of the water.

How does water get into the cyl? The O-ring would stop it.

 

[kboater]

I'm wondering the same thing. You are correct it has o rings instead of traditional head gaskets.

 

[kboater]

I'm wondering the same thing. You are correct it has o rings instead of traditional head gaskets.

 

[daselbee]

Two things kboater.....I am skeptical about the work done so far...sorry.

1. Have you personally seen the water on the spark plug? Do you know absolutely for sure that it is getting water on it?

There is a seal around the end "butt" of the crankshaft. This is down where the driveshaft splines in to make the physical connection between the two.
Then there is a bottom crankcase head, which typically has large o-ring around it. So, two sealing points.

Here is the deal.....crankcase compression is critical to proper operation of the engine. This is NOT cylinder compression. Crankcase compression, where the rods and crankshaft live. So, if you have low crankcase compression due to a leak in either of the two places I just described, what happens is that the engine will not receive a full fuel/air charge on the affected cylinder.
When the piston is going down in the cylinder, it creates crankcase compression. When going up in the cylinder, is creates a vacuum in the crankcase.
So you can see, that your symptoms could be caused by a leaking lower crankcase seal. Going up, is sucking in water, going down, it fails to gen enough crankcase compression to get an effective fuel air charge.

But here is the rub. That failure in my opinion is rare. To me it is a longshot. So, the last thing I would do is rip open the powerhead when other problems might be at hand.

First verify the water in the cylinder question to your satisfaction. If so, proceed as you see fit.

2. I don't think he has completely cleaned the carbs. No one ever does. (in my opinion.) The carb system consists of the black plastic carb bodies, AND the throttle bodies. Those throttle bodies have the very small holes that feed fuel at idle and midrange. The holes are located behind a small plate held on by two small Phillips screws on your engine. Behind that plate, in the calibration pocket, are the holes. They must be clean.

You have said nothing about him cleaning the throttle bodies. Has he? Does he know what I am talking about? This issue is applies only to engines that have black plastic carbs attached to throttle bodies. Engines with metal carbs have the idle fuel bleeds drilled directly into the body of the carb. They still need to be cleaned, but they are not separate from the "carb" as they are on yours. He sticks fingers into the throat, chokes the cylinder, causes more fuel to flow on that cyl, and you get response from the cylinder. To me, it is well worth checking the throttle body on that cyl.....
I would surely do that before yanking the powerhead. See my point?

 

[Chris1956]

The block and head have several water passages all around the cylinders. The OEM service manual advises to put a bead of silicone around each water passage to assure it seals to the matching one in the head.

 

[kboater]

Two things kboater.....I am skeptical about the work done so far...sorry. 1. Have you personally seen the water on the spark plug? Do you know absolutely for sure that it is getting water on it? There is a seal around the end "butt" of the crankshaft. This is down where the driveshaft splines in to make the physical connection between the two. Then there is a bottom crankcase head, which typically has large o-ring around it. So, two sealing points. Here is the deal.....crankcase compression is critical to proper operation of the engine. This is NOT cylinder compression. Crankcase compression, where the rods and crankshaft live. So, if you have low crankcase compression due to a leak in either of the two places I just described, what happens is that the engine will not receive a full fuel/air charge on the affected cylinder. When the piston is going down in the cylinder, it creates crankcase compression. When going up in the cylinder, is creates a vacuum in the crankcase. So you can see, that your symptoms could be caused by a leaking lower crankcase seal. Going up, is sucking in water, going down, it fails to gen enough crankcase compression to get an effective fuel air charge. But here is the rub. That failure in my opinion is rare. To me it is a longshot. So, the last thing I would do is rip open the powerhead when other problems might be at hand. First verify the water in the cylinder question to your satisfaction. If so, proceed as you see fit. 2. I don't think he has completely cleaned the carbs. No one ever does. (in my opinion.) The carb system consists of the black plastic carb bodies, AND the throttle bodies. Those throttle bodies have the very small holes that feed fuel at idle and midrange. The holes are located behind a small plate held on by two small Phillips screws on your engine. Behind that plate, in the calibration pocket, are the holes. They must be clean. You have said nothing about him cleaning the throttle bodies. Has he? Does he know what I am talking about? This issue is applies only to engines that have black plastic carbs attached to throttle bodies. Engines with metal carbs have the idle fuel bleeds drilled directly into the body of the carb. They still need to be cleaned, but they are not separate from the "carb" as they are on yours. He sticks fingers into the throat, chokes the cylinder, causes more fuel to flow on that cyl, and you get response from the cylinder. To me, it is well worth checking the throttle body on that cyl..... I would surely do that before yanking the powerhead. See my point?

Thanks so much for your detailed response. I have personally seen a drop of water on the spark plug in cylinder 4 as he describes.... He is basically saying due to that water, that plug and cylinder are not firing. Then, by manually choking that cylinder it gets more fuel, plug dries off a little, and starts sparking again..... Does this sound possible? Since I did see the water in the plug myself (just a little) do you think we should proceed with the tear down? Or work more on the carbs and throttle body as you suggested (although I have personally seen the water)?

 

[Faztbullet]

The block and head have several water passages all around the cylinders. The OEM service manual advises to put a bead of silicone around each water passage to assure it seals to the matching one in the head.

This is so it wont leak from mating surfaces as head dont have water passages except for at t-stat and dump openings.... Its not the lower seal as its not in contact with adaper plate and water never comes in contact with it. The only way water can enter cylinders on this motor are: bad reed, cylinder liner has turned(have seen) and glue line from when block was cast leaking(common problem). If this is a salt water motor it could have a pin hole eaten thru the block internally from water passage or in the exhaust runners which if the case the block is junk.

 

[daselbee]

do you think we should proceed with the tear down? Or work more on the carbs and throttle body as you suggested (although I have personally seen the water)?

I guess you missed my point. What is the easiest path?

Also, listen to Fazt....voice of extensive experience. I am going to also say that leaking lower seals is not likely.

 

[kboater]

After talking to the mechanic again, he is sure there is no carb issue. He said there is no removable exhaust on this motor, and he is fairly certain there are no pin point leaks in the cylinder. We have already ruled out the heads and head gaskets (as those were already done). It'd just #4 cylinder that is getting a little moisture on the plug. Here is his response to why he thinks it's the lower main seal. I'll keep everyone updated Pin holes are possible but not likely there didn't appear to be any aluminum transfer from excessive overheat which would limit the possibility of pin holes in the cylinder .as for the one post that stated the carburetor was out of adjustment if I could put my hand over the front it is definitely a adjust issue . This also is incorrect there is only one adjustment and it is a intake adjustment the only way to adjust the carburetor us to change the jetting and this is simply not the case with yours . Yours however is the inability to efficiently pull fuel due to the loss of vacuum as well as water breaking down the octane with water

 

[daselbee]

Again, I have to disagree.
Going by your post, Johnson 2000 90 hp, the parts pages clearly show an idle mixture needle adjustment. Ref #34 on the parts pages.
Since you didn't post the model number, I have assumed a J90PLSSE, but the carbs are all the same anyway, from model to model.
So, your statement that the only way to adjust the carb is to change the jetting is not correct. We are talking idle problems, right?

I do not understand the statement that the only adjustment is "an intake adjustment." Makes no sense.

OK...again I ask you......what about the throttle bodies? You keep referring to the carbs, but I posted about the throttle bodies, and you keep skirting the answer.
Has he cleaned the calibration pockets behind the small plates attached to the sides of the throttle bodies OR NOT?

If you have a clog in there, the cylinder will not pull properly, while the other cylinders will work to keep the engine running.

OK here is a test....what is the idle mix screw on #4 set at, turns out? Now the others? Turns out? Try adjusting #4 idle screw in and out to see if it has any effect on the motor running. If all is clean in there, it should affect the engine....either lean sneezing, or excessive oil floating on the water in your tank due to a very rich condition.

Now you are gonna tell me you are doing this on muffs....right?

 

[kboater]

Again, I have to disagree. Going by your post, Johnson 2000 90 hp, the parts pages clearly show an idle mixture needle adjustment. Ref #34 on the parts pages. Since you didn't post the model number, I have assumed a J90PLSSE, but the carbs are all the same anyway, from model to model. So, your statement that the only way to adjust the carb is to change the jetting is not correct. We are talking idle problems, right? I do not understand the statement that the only adjustment is "an intake adjustment." Makes no sense. OK...again I ask you......what about the throttle bodies? You keep referring to the carbs, but I posted about the throttle bodies, and you keep skirting the answer. Has he cleaned the calibration pockets behind the small plates attached to the sides of the throttle bodies OR NOT? If you have a clog in there, the cylinder will not pull properly, while the other cylinders will work to keep the engine running. OK here is a test....what is the idle mix screw on #4 set at, turns out? Now the others? Turns out? Try adjusting #4 idle screw in and out to see if it has any effect on the motor running. If all is clean in there, it should affect the engine....either lean sneezing, or excessive oil floating on the water in your tank due to a very rich condition. Now you are gonna tell me you are doing this on muffs....right?

Thanks for your response. I'm not trying to skirt any questions. I have no idea if the mechanic has messed with the throttle bodies or checked them. As far as idle adjustment goes, again, it's at the mechanics, so I am only going by what he is telling me. But my question would be, regardless of good or bad throttle body or idle adjustments, I'm assuming there should be no water moisture on the plug.....? Which is why he is trying to chase down as to why there is water moisture on the plug. Could either a bad throttle body or idle adjustment screw needing adjustment cause water moisture on the plug? I'll try to swing by today and check for an idle adjustment screw myself Thanks

Edit: yes he is doing this on the muffs

 

[daselbee]

No water can come from the throttle body or idle adjustment screws, ASSUMING there is no water in the gas.

 

[kboater]

duplicate post

 

[kboater]

Here is an update. The mechanic pulled the block to look at the lower seal. It was toast from being over heated at some point and also has a crack in it where we think it was letting water leak into #4 cylinder.  So lower seal has to be replaced. Mechanic (who I trust) said that the block had to be split to change out that lower seal. Now here is my question, if the block had to be split to change this seal, would you have go ahead and have the mechanic pull the crank and pistons to inspect and and check rings since he will already have the block split? Remember there was a light coat of surface rust in #4 cylinder so we don't know long it was leaking. It will cost more money to pull and inspect everything, but mechanic is suggesting this so we can be 100% sure there is nothing else wrong. Obviously money is the problem (like usual) or I would of course say yes. What do you guys think? Go ahead and pay more to pull crank and pistons to inspect since already have to split the block?