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1990 Johnson 115 bogs under load

Dale_Mitch

New member
I have a 1990 Johnson 115 that bogs under load. The motor will start and idle all day long with out issue. The problem is once I put it in gear and try to speed up, the motor will only get up to about 4 mph and then bog down. I have replaced and clamped all fuel lines, vacuum lines and connections from the tank through the pump and into the carburetors. I rebuilt the carburetors so the needles would seat properly. I then replaced all 4 spark plugs and spark plug wires. I have determined that the motor is bogging because it is getting too much fuel. What would cause the motor to get too much fuel if the carbs are clean and rebuilt to operate properly? Is it possible that my motor is getting the right amount of fuel but I have an ignition problem that can’t burn it fast enough? The one thing that scares me is I did a compression test when the motor was hot and my numbers read 125, 110, 110 and 90. I’m thinking my issue may be in the stator or the power packs if it’s is indeed an ignition issue, but I’m afraid to replace those expensive parts if it’s possible that the low cylinder at 90 is the reason my motor won’t run right.
 
Sorry ----You need to take the cylinder head off on the side with 90 PSI.-----Lucky you if it is just the head gasket blown.-----But I think you will find broken bits of piston rings smashed on the piston and cylinder head.----That has happened and will happen to all these crossflow engines !!!-------The fact that it will idle all day long and even run means that these are really well built motors.----All except for the design of the top piston ring !
 
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If it is a blown gasket or piston ring is it possible for the motor to run WOT sometimes? When i first started having the bogging issue I brought it in my garage and started replacing parts I would take it back out and test drive it. During the test drive I was able to get the boat to take off and plane out and run fine but then the next time I had it out I would have issues again. It hasn’t gone over 5mph the last 3 times I have tested it though and I think I am out of cheap things to fix and try out. Is there anything else you think I should try that’s easy or cheap before I tear the motor down again?
 
I believe post # 2 is very clear !!------But perhaps you are waiting for an answer that you want to hear.------Take the head off now.----There is something wrong with your motor !!----Rebuilding the carburetors is often the first thing a novice will try.-----But that won't fix your motor.
 
I believe post # 2 is very clear !!------But perhaps you are waiting for an answer that you want to hear.------Take the head off now.----There is something wrong with your motor !!----Rebuilding the carburetors is often the first thing a novice will try.-----But that won't fix your motor.

Rebuilding the carbs was the first and cheapest thing to do since the symptom was a fuel related issue. I am not waiting for an answer to hear I want to hear I’m just simply asking if there are other possible things that could make my motor do this before I order more parts and wait for them to come. I am ordering a new head gasket since it is cheap and will be replacing that although I don’t have any signs of a bad head gasket besides low compression. There is no fuel seepage around the edge of the gasket and there is no sign of water getting into the piston. This leads me to believe it is a piston ring issue like you said but I’m not sure I want to tear down to get to the piston rings just in case the cylinder wall needs to be honed out. I don’t have the tools or know how to hone out a cylinder and I don’t want to try to bring it into a shop torn apart. Shops are very expensive which is why I was asking if there is anything else I need to check before I start throwing money at larger parts.
 
Sorry ----You need to take the cylinder head off on the side with 90 PSI.-----Lucky you if it is just the head gasket blown.-----But I think you will find broken bits of piston rings smashed on the piston and cylinder head.----That has happened and will happen to all these crossflow engines !!!-------The fact that it will idle all day long and even run means that these are really well built motors.----All except for the design of the top piston ring !
In your opinion,what is wrong with the design of the top piston ring that is used on avery3.5 crosstown and looper?
 
Cheap and easy,is your timer base advancing All the time? Are the carbs opening up All the time? Does it act up with cowling off? Is it running on all cylinders by doing a cyl.drop test? Put a timing lite on and watch you spark...none of this will fix low compression.there's lots to check,but you have to do it.
 
Just wanted to see if YOU were out there.[/QUO
Suup, I gotta say i'm a little surprised you don't know why crosstown rings break. I will let you get back to your muffs. A must have diagnstic tool:cool:

To Dale_mitch if you find the piston ring is broken you can do most of the work yourself. With a broken ring your motor will need to be bored. You will need to do all 4 cylinders and replace all 4 pistons. If you broke a ring you will see it immediately on the piston crown. You can get a WSM kit for a very reasonable price, and some let you upgrade to a Wiseco piston for a small fee. The Wiseco does away with the top ring design, a WSM piston will use the wedge ring. If you go that route you should be able to rebuild your motor for about $12-1500 dollars. The WSM kit nas everything you need to rebuild your motor.
 
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I had to get new spark plug wires that I he ordered before I was able to do a drop test. I also got connectors for all 4 plug wires that allow you to see the spark going to each spark plug. Once I could see that my spark was fine I did the drop test. When I pulled the plug wire on the low cylinder with only 90psi, the motor didn’t skip a beat and just kept idling. It was idling high though, anything under 1600rmp and it would die because it was only running on 3 cylinders. I’m guessing I need new parts in the piston and the cylinder wall will probably need to be honed out. I’m taking it in to get it done professionally and then have a tuneup done on it after. Thank you all for the advice and extra things to check!
 
Not easy to find a shop that will rebuild it.----They might opt for an exchange powerhead.----Still going to be a hefty sum of money.
 
I had to get new spark plug wires that I he ordered before I was able to do a drop test. I also got connectors for all 4 plug wires that allow you to see the spark going to each spark plug. Once I could see that my spark was fine I did the drop test. When I pulled the plug wire on the low cylinder with only 90psi, the motor didn’t skip a beat and just kept idling. It was idling high though, anything under 1600rmp and it would die because it was only running on 3 cylinders. I’m guessing I need new parts in the piston and the cylinder wall will probably need to be honed out. I’m taking it in to get it done professionally and then have a tuneup done on it after. Thank you all for the advice and extra things to check!
There is no reason you cannot rebuild that yourself. Get a factory manual and do it.
 
There is no reason you cannot rebuild that yourself. Get a factory manual and do it.


I could probably do it but I would still need to get the cylinder honed out and I dont know of anywhere around me that will do that for less than $500 and the other parts look like they will cost about $600 after shipping. Have you ever rebuilt a cylinder and what was your experience with it?
 
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