87 Johnson wont start, good spark. Fuel? Compression?

[gdavies07]

I did a compression check on my motor earlier. 55 psi on both cyl cold at wot. Tester was bleeding out without releasing pressure from bleeder valve, Autozone rental. After messing around with the bleeder valve on the tool I was able to keep the reading until I released the pressure. Fuel bowl in carb was dry when I removed the high speed screw. Top spark plug was black & dry but great spark, bottom plug was wet with great spark, both plugs were recently replaced by the looks. The PO said it ran great & strong & boogied along until the last time he was out. Motor kept stalling and losing power. He used the electric prime/choke to keep it running then it finally died and left him paddling. For $400 for bmt & tons of accessories I couldn't say no, I bought it. Fired right up today and purred for a couple seconds by squirting a gas-oil mix into the carb. I put my hand infront of the carb when cranking and vacuum felt good enough to pull fuel so that's what led me to the squirt test. I've researched the forums all day and the with even compression makes me think its a bad head gasket, but it fired right up with a squirt of fuel?! Could the compression be ok where it was cold, around 50 degree air temp so ? Bad comp tool? The PO seemed honest on what happened. He's the father of 3 girls and owner of a 25' WA and didn't have time to get into it he said. The fuel pump is on the bottom cyl and with a wet lower plug makes me think the diaphragm is leaking into the bottom cyl. My plan tomorrow is to pull the fuel pump and prime the fuel line bulb to see if it pees fuel from the vacuum port. Am I correct to think that the primer bulb should force fuel through the pump and into the carb bowl regardless of the condition of the fuel pump diaphragm? With Ethanol fuel, it makes me think it may have rotted the diaphragm, With the low comp reading it makes me think its not pushing and pulling the diaphragm, with even comp on both cyls it makes me think either a bad tool or bad head gasket. The last owners story sounds like fuel starving and makes me think its not the low comp. Any ideas of what I can do before tearing apart the power head. I'm on a very low budget and very unfamiliar with 2 stroke engines and outboards. I did buy the repair manual but didn't find alot of troubleshooting info, and now feel more confused by reading all the forum related posts. Thanks for any and all suggestions and help!!

 

[gdavies07]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

And I meant to add... Would Seafoam be effective in any way where I can't run the engine in an attempt to boost the compression if it is low? I do see quite a bit of carbon looking through to spark plug holes. I can't see any scoring on cyl walls or metal on the pistons. Is there something that would be effective to help build compression in a non running motor other than a little 2 stroke oil? Would fogger help and how so if it would?

 

[Jeremy78]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

All that info and you never said the size of the motor. 55 on compression is way to low. I would save my money and rebuild the motor. you are having fuel problems because of the low compression.

 

[JB]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

In a very low HP, rope start engine 55-55 could be okay, but more likely it is a head gasket blown between the cylinders.

Without knowing the exact model we can only speculate.

 

[gdavies07]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

Sorry about that, it was late, and I was getting tired after reading post after post. 30 hp, Mod: J30ELCUB. Electric start. As far as priming the fuel bulb...should that force fuel into the carb bowl? I'd much rather replace a head gasket cost wise than a fuel pump. But with ethanol fuels here it makes me think the diaphragms or fuel line might be rotted & possibly clogging something. Like I previously mentioned, I don't have alot of $ so I really don't want to start tearing things apart and replacing gaskets or pumps until I feel a little more comfortable with the actual problem. Carb will be rebuilt this winter but I'd like to get it running before I get into other things. Compression was low IF the tool was right on its reading. But as I read here there's mechanics with 5 compression tools in their shop that give reading of a 20 psi difference from one another, and the motor was cold, and there was alot of carbon build up. The fact that the readings were so close and the PO was describing some sort of fuel starvation (using the electric fuel prime). Does his description of symptoms sound like a head gasket? Would low compression/ low vacuum scenario still allow the fuel pump to operate enough to use dump fuel into the manifold via the electric fuel prime via the push in key? Or because of low compression would the pump eventually fail all together? I'd think, if it was operating enough to feed fuel to the manifold then it should feed fuel to the carb. But I in no way understand too much about 2 strokes, or outboards. But I'm very knowledgeable in 4 strokes, autos, and electronics diagnostics.

 

[JB]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

I think you need to confirm or eliminate the head gasket before you go farther, GD.

Good luck.

 

[gdavies07]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

Ok so as I've already mentioned at least twice in my previous post is that I don't have a lot of money and risking a broken head bolt on a 24 year old motor doesn't seem cost effective "at the moment". A head gasket is cheap yes, but removing a broken bolt is not. Of all my unanswered questions, is there someone who knows if priming the fuel bulb should send fuel through the pump and into the carburetor bowl? Because if my understanding is correct from what I'm looking at this system the fuel pressure from the primer bulb should flow through the fuel pump and into the carb. Unless there is a problem somewhere in the fuel system. Isn't that a little more cost effective before tearing into a 24 year old ocean used head?

 

[Monte1961]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

Parts and repairs cost money. 55 psi is to low on a electric start motor. Pull the head and inspect! Or just keep guessing. Your choice.! TIP: A little bit of heat goes a long way!

 

[gdavies07]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

I agree Monte, although, there is a big difference between me guessing, and me asking for help and suggestions on certain questions that I have, parts and repairs do cost money where as diagnosing the actual problem cost mostly time. But pulling a head that didn't need to be now cost me money, time, and a 4 day wait for a new gasket, and time to clean the head mating surfaces. Seeing as though I was already having problems with the compression tool as described, and the motor was cold during the comp test which I've read here in this forum that a cold compression test is pretty much useless, and a lot of posts describe how compression tools differ in reading from one another, and the readings were almost exactly the same, and the previous owners description of the problems sounded like fuel starvation, I was hoping for some help diagnosing the fuel system. As suggested by others, I pulled the head off and found no signs of a blown head gasket, no signs of carbon or blow-by between the cylinders. no scoring on the cylinder walls. I don't even feel wear from the rings. I've rebuilt auto engines in the past, I could feel the lip on the cylinder from where the rings stopped their stroke. So that leads me to believe there's nothing wrong with the rings either. So I "guess" a good suggestion would have been to get a comp tool that is known to work where as I stated the tool was already giving me issues. Yup, Kicking myself in the rear now!

 

[gdavies07]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

Question. While I was preparing the surfaces for the new head gasket, I noticed what looked like vacuum tubes pressed in the water cooling passages around the cylinders running parallel with the cylinder in 3 locations. To redirect water flow to hot spots? I thought at first they were pieces of a water pump impeller, but they're definitely a tube and strategically placed. Why would someone do that? Is this common practice for a troubled powerhead?

 

[Jeremy78]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

I have used very expensive compression checking tools and I have used very cheap ones. I have never seen the difference. What monte1961 was trying to tell you is that you have a boat and it is going to cost you money to run and fix it. I have seen a 15 pound difference in compression when outside temps have fallen. That little extra heat might be enought to get your compression up to start your motor. Also, unless we are right there with your to look at your motor all people can do is give there best guess. Have you cleanned the carb. Have you done a spark check, do you have a manual.

 

[boobie]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

As long as you have the head off, replace those little tubes you see in the block. They direct water in the proper direction so you don't get hot spots in the block causing it to overheat.

 

[AlTn]

Re: 87 Johnson wont start, good spark. Fuel? Compression?

marineengine.com has diagrams and part numbers and names for parts for your motor...as to the primer bulb and primer, I've used clear vinyl tubing in place of the fuel line from the pump to these parts and the carbs to diagnose fuel pump or fuel delivery problems and it's been effective as you can see fuel or air bubbles in the line...I don't recommend you use this as a permanent fuel line however