2001 Johnson 115 Blown Piston

[asignabove]

5 months ago I purchased a used 2001 Johnson 115hp Ocean Pro on a 2001 Sea Hunt. When I bought the boat the dealer stated that the motor was thoroughly checked out and was in excellent shape and had compressions of 145/145/150/150. Since then I have ran the motor around 15 hours. While using the boat the other day running at about 4200 RPM for about 10 minutes the motor lost power over about a 5 second period and finally stopped. It had to sit about 20-30 minutes before it would start up again and when it did it ran rough. The motor did not make any unusual noise before or after the shut down. We trailored the boat and took it back to the dealer to be checked. They advised me that the #1 cylinder had no compression and wanted to tear it apart to see why(upset with the dealer I declined). I got the boat home and looked in the spark plug hole and saw a large hole in the piston. Then removed the head and the hole was at least the size of a half dollar with the sleeves destroyed and possibly damaging the block. The head had very little damage to it considering the size of the hole. The dealership failed to put my original plugs back in so I can see what kind of shape they were in. My question is what could cause this on such a new engine and should there have been signs prior to this that something was going wrong? Another question is if the block is damaged is it worth replacing the powerhead and rebuilding or should I just ditch that motor and go new? Going out on a limb here is it possible the dealership when checking it out did something to it and are trying to hide it? Because it is odd that they would place new spark plugs in a motor that will not run and not even charge me for them.

 

[Dhadley]

Re: 2001 Johnson 115 Blown Piston

First, welcome! And sorry to hear of the troubles.<br /><br />Anyway, if the motor was damaged when you bought it you would have known right away. It would not have run flawlessly for 1 hour let alone 15. Something caused the piston damage. Lets find that cause.<br /><br />You didnt mention but can we assume this is a carb'd motor?

 

[asignabove]

Re: 2001 Johnson 115 Blown Piston

I believe it is carb and not fuel injected.

 

[Dhadley]

Re: 2001 Johnson 115 Blown Piston

OK, seems logical since you didnt mention having to fool with injectors when you removed the head. Just making sure so we dont go down the wrong road, so to speak.<br /><br />Let me say that, believe it or not, its not uncommon for guys to replace the spark plugs right away instead of taking compression. I dont know why but thats the way it is. <br /><br />Anyway, I know youre upset with the selling dealer as far as working on the motor. Understandable. However if there was any type warranty it might not be a bad idea to see what he offers. If that dealer is out of the question look for another thats certified in OMC/Bombardier. <br /><br />Theres two things we have to concentrate on. 1- what caused the hole in the piston. Detonation? Sure, but what caused the motor to go into detonation? What brand and type plugs were in it? Is the motor double firing? Is the center hub magnet on the flywheel still in place? What fuel and how old? Is the number 1 carb clean? What was the timing set at? Lots of questions.<br /><br />2- get the motor apart to assess the damage. Once its apart we can see if it can be bored or if a replacement sleeve is needed. <br /><br />Some other info may be helpful also. What was the top rpm? Wtaer pressure? Type of fuel / age of fuel and spark plugs play a big role. Any water in the fuel filter? Post back with as much info as possible. Some of these answers will have to come fro a tech most likely.<br /><br />Good luck!

 

[Reelly]

Re: 2001 Johnson 115 Blown Piston

A hole in the center of piston is usually a sign of preignition. Either the timing is too far advanced or there was other issues causing the preigniton. This could have been caused by numerous things but if not the timing advance there was something that caused internal engine damage before the preignition happened. The only true way to tell is to tear it down. If there was major piston damage the deposits of piston are placed on top of piston and head which will turn red hot during operation. Thus acting like a spark plug and igniting the mixture prematurely. This premature explosion rams into the top of the piston causing the hole you see. Did the dealer rebuild anything on motor, carbs etc?

 

[Reelly]

Re: 2001 Johnson 115 Blown Piston

I agree with dhdadly. I have also seen this when someone was running too low of octane. This low octane will burn much faster than the high octane beleive it or not. But usually there other facters involved as well.

 

[Reel Precision]

Re: 2001 Johnson 115 Blown Piston

Let me reword that. The lower octane has a lower flash point so this causes the mixture to go off faster. The higher octane burns hotter but this because it burns slower. If you build a fire and let it burn longer it will get hotter.

 

[asignabove]

Re: 2001 Johnson 115 Blown Piston

OK, the answers I know of as of now. I don't have the original spark plugs to know what plugs were in it, because the dealer kept them and I did not find out until the boat was home hours later. The motor was inspected and tuned by the dealer prior to the sale so it was the plugs they put in. Fuel was less than 2 weeks old and was 87 octane(what the dealer and johnson recommends) boat never sat more that 2-1/2 weeks without being ran. I never ran it over 5000rpm and that was for less than 1 minute. Water pump was changed at time of purchase and was a strong pressure out the water outlet even after problem. As for the flywheel I will have to find out.

 

[Dhadley]

Re: 2001 Johnson 115 Blown Piston

Good choice on fuel. What spark plugs are in it now? Most likely the dealer put the same type in this time as he did last time.<br /><br />Was 5000 the most it would turn?

 

[asignabove]

Re: 2001 Johnson 115 Blown Piston

Plugs are Champion QL78YC.

 

[asignabove]

Re: 2001 Johnson 115 Blown Piston

5000 was the most I did, but it seemed like it would do more. I tried to baby it because I wanted it to last.

 

[Dhadley]

Re: 2001 Johnson 115 Blown Piston

Good choice on plugs too. <br /><br />I take it you dont have a water pressure gauge. You might want to consider one after we get going again. <br /><br />When you turn your key "On" the warning horn should beep once. Thats the "self test" mode. If that works, most likely the alarm system works. And vise versa.<br /><br />We're fairly certian the basics are OK, as long as the horn works. The rest of the answers will have to come from the tech that performs the work. <br /><br />Once the rebuild is done the tech will have to spend some time figuring out what caused the piston to burn if its not been determined by then. And you want to make sure the motor is set up so that top rpm is 5800 to 6000 with an average load. That will asure that its not being lugged at any given rpm. <br /><br />The next step is to start the rebuild. Whoever is doing it will have to look over those things we talked about earlier. Just remember, there is a reason and it can and must be found. <br /><br />Good luck!

 

[asignabove]

Re: 2001 Johnson 115 Blown Piston

If I find out when we tear it apart that the block is damaged, is it still worth rebuilding or should I go to a new powerhead or new motor?

 

[Dhadley]

Re: 2001 Johnson 115 Blown Piston

Lets see what it looks like. Generally speaking if the crank is OK, and I would bet it is, then its worth rebuilding even if it needs a sleeve in number 1. <br /><br />Just to get some background, look here in iboats at replacement prices. Remember these are bare powerheads and they will have to be dressed with your carbs, ignition etc.<br /><br />There is always the advantage of a new motor with the warranty etc. Thats something to think about. If you decide to go that way and want to sell yours, as is, let me know. We can probably find a home for it. <br /><br />Keep us posted!

 

[asignabove]

Re: 2001 Johnson 115 Blown Piston

Thanks for all your well needed help....I will keep in touch.

 

[Dhadley]

Re: 2001 Johnson 115 Blown Piston

Sorry I wasnt more help. Hang in there, if you chose to fix it I'm sure it will turn out to be a great motor.<br /><br />Hey, one more thought -- when you pulled the head off, there should have been some silicone sealer type substance. Look at the top and bottom water passage openings -- are the openings partially closed? And look at the thermostat on that side. What does it look like?

 

[bollard]

Re: 2001 Johnson 115 Blown Piston

Could it be possible that there was a carburation failure causing the one cylinder to lean out and burn the piston? <br />Just a thought because a rebuilt powerhead with the old carbs could spell trouble later on.

 

[Cricket Too]

Re: 2001 Johnson 115 Blown Piston

E., When you do get it back up and running, and I'm sure you will, there is no harm in running this motor over 5000 or evn 5500 rpm, all day long if you want, assuming it is propped correctly. 2 strokes are a different animal than 4 strokes and it is a common misconception that lower rpm and never running WOT will add to your engine life and that running high rpm's alot will hurt it, car engines yes, 2 strokes no. Good luck.

 

[bonitoman]

Re: 2001 Johnson 115 Blown Piston

I live 5 minutes from you in Sanford. Email me so I could take a look at your engine. jsapo@cfl.rr.com