Need help on piston failure

reeldutch · Feb 10, 2005

Re: Need help on piston failure

well if there is only one cylinder damaged ore piston than it is defenetly NOT vro pump failure. i thought all 4 pistons and cylinders looked like your pic. that is a big difference . buying an outboard over the internet is a big risk. i would only buy a rebuilder for a couple hundred from ebay but thats as much risk as i would take. and still you dont know what you buy. so if i get it right you have all 4 cylinders rebored and only one has damage or ?????

Dhadley · Feb 10, 2005

Re: Need help on piston failure

You can still go, if needed, to .044 and .064 oversize on that block. No problem. If the finished bore size was too tight, the extra oil could possibly avoid a problem until you went without it. Probably not the cause but its something we have to look at. Then, we have to look at what happened in the first place. If this is a repeat, then it will happen again unless we find and correct the cause. So, tell us what happened to the first powerhead. Was it the same thing? Next we need to know what the timing was set at, if at all, and by what method. When you ask the dealer, get him to be specific. "By the book" is not an answer. We also need to know if they drained and replaced the oil in the tank. If the first failure was the same and the oil was not changed, there could be water in the tank. Extremely common and easy to happen. Again that would explain why it happened after the extra oil was taken away. If the boat has been sitting for a day or so you can carefully disconnect the oil line and pump some into a cup or jar. If theres water in there it will come out first.

Cortes165 · Feb 10, 2005

Re: Need help on piston failure

Reeldutch.......all 4 pistons have the same damage. Dhadley....The oil tank was definitely drained , cleaned and new oil was poured in. I don't know how water would get in there after this procedure, but I can check the tank to see if there is. Didn't mention this before, but would using a full synthetic TCW3 oil hurt?? Ok, I better quit now. You guys have asked questions that I cannot answer. It's going to take me a couple days to get answers. Thanks again for the help. There is an overload right now, but like several have said, I need to find the cause before trying to rebuild.

Dhadley · Feb 10, 2005

Re: Need help on piston failure

No problem. We'll be here when youre ready. The oil should be OK. Probably better than OK. BTW, if its OK to ask -- who did the boring?

lawyertob · Feb 10, 2005

Re: Need help on piston failure

Okay, I hate to jump in here with the big dogs and experts...but my first impression was that the cylinders were not washed after the boring. It looks like an amateur bored the cylinders and just wiped them clean...and we know that a rebored cylinder just doesn't come clean unless you wash it...I know some people will look at you crazy when you tell them to use soap and water on a nice shiny just bored block. Anyway, the vertical scoring and little or no wiped areas make me think that it was work hardened metal left over from the boring. But then, I am a rank amateur when it comes to outboards, so I will shut up now.

Maybe just maybe $0.02 worth, Joe

walleyehed · Feb 10, 2005

Re: Need help on piston failure

Joe, that's what I was getting at by saying contamination above......looks too perfect on the scoring to me, but Dhadley will drag some clues out of him and the cause will show it's face. I feel the same as you though...

Dhadley · Feb 10, 2005

Re: Need help on piston failure

Agreed about the "not so clean" deal but it did run long enough to burn 40 gallons of fuel. It sure seems it would have tore up sooner than that. Maybe not, we'll see. LubeDude -- be careful about making statements that may mislead someone. That is obviously not a Wiseco piston. And the Wisecos do not need extra clearance compared to cast pistons. It may well turn out to be a clearance problem but if the cylinder was not bored properly thats not the piston manufacturers fault. No matter who made it. We just have to be patient until Cortes165 can find out from the machinist what he used for a finished bore size. If its who I think it is that bored it, I'd bet the finished bore size was correct. The clue is going to be in the original damaged pistons and these damaged pistons. Cortes165 has yet to say what the original problem was.

rodbolt · Feb 10, 2005

Re: Need help on piston failure

Dhadley I agree there. whatever the cause is most likely the cause of the original failure. the old wiesco pistons had to have extra clearence. a problem they solved many years ago. however I have seen some stick due to bad or removed thermostats due to the piston expanding and the cyl did not. they call it a cold seizure and wont warrenty it. but what it looks like is a clearence problem. why it ran out of clearence must be determined. most my experience with oil related failures usually will show marks on the rod and wristpin bearings. it is possible that the transfer port covers are not being removed for cleaning. I have seen that as well. maybe some less close up pics and pics from other directions will help as well. but I have built to many crossflow jonnyrudes to believe there is a flaw in the design. Cortes165. has the exhaust divider plate been removed for inspection?

Dhadley · Feb 11, 2005

Re: Need help on piston failure

That brings up a very interesting point Rodbolt. I hope we're not getting too far off the track of helping Cortes165. Especially since that is not a Wiseco piston. Anyway, do you believe they (Wiseco) should warranty the piston damage if the t-stat is missing or is not operating correctly? IE -- if the motor is operating differently than it was originally designed to?

rodbolt · Feb 11, 2005

Re: Need help on piston failure

dhadley no they should not.the instructions with the last set stated it.that is like yamaha warrentying varnised up hp pumps. they will but i dont think they should.

Dhadley · Feb 11, 2005

Re: Need help on piston failure

Thanks Rodbolt. Good info.

reeldutch · Feb 11, 2005

Re: Need help on piston failure

so if i understand it well the 50:1 + VRO kept the engine running altough there wasn't enough clearence. and as soon as he only used the vro the oiling kould not keep up with the friction? sounds good. but if you have impropper clearance shouldnt your engine overheat deu to extra friction? and why didnt his alarm go of then? assuming there are tstats in.

Dhadley · Feb 11, 2005

Re: Need help on piston failure

We dont know if it was a clearance issue or not. He's getting the finished bore size from the machinist. That will tell, but right now we dont know.

rodbolt · Feb 11, 2005

Re: Need help on piston failure

reeldutch thats why they call it cold seizure. in certain cases especially if its a forged piston the piston heats up but if the t-stats are open the cylinders and heads never do. in a perfect world the skirts never actually touch the cyl walls. the heat from the piston is transfered by the piston rings to the cyl walls. however in certain cases its possible the piston expands more rapidly than the cyl wall,aggrevateded by no t-stats, and will cause the piston to swell into the cyl walls. years ago when I was a pup wiesco instructions said to let the motor idle for 8 hours for breakin. then they came out with a different finnised bore size then they finally figgured it allout and use the standard bore size. but the cold seizure problem stillcan happen. however with the smallpart of the pic I saw with no ringland or dome shots I cant say what happened other than the piston had some type of interference with the wall.

johnrude · Feb 11, 2005

Re: Need help on piston failure

Call Kurt at Mat-Fab. All they do is outboard blocks. You can get there number at www.mar-fab.com. He should be able to help you figure out what happened. When in doubt talk to the pros.

walleyehed · Feb 11, 2005

Re: Need help on piston failure

As for the sake of Pros, I realize not everyone here knows who's who, so that being said, Dhadley has worked with Mar-Fab and many, MANY top-notch shops. Mar-Fab would tell you to call Dhadley. Best Techs available are right here. 931-738-2815....ask for Kurt or Dan if you must call...tell them your story and also let them know Dhadley is on the scene...they'll refer you back to him....

reeldutch · Feb 12, 2005

Re: Need help on piston failure

yep, i'm only a driveway wrench and dont have any real educated noledge like the pro's. i am really intrested in outboard stuff and its mysterys. i'm just hoping we can figure this all out. thanks rodbolt for explainig, it makes sence to me now. reeldutch

Cortes165 · Feb 17, 2005

Re: Need help on piston failure

Info is coming, it just takes a while to gather. Anyways, to get better pics, I removed the rod from the piston. The wrist pin bearing fell out in about 30 pieces (28 pins, 2 washers). I have never seen a brg like this. I have installed several (in diff engines) and the brg is always held together with a cage. Is this the normal setup?? It must be a real pain to reassemble? This is the least of my worries, I was just curious.

LubeDude · Feb 17, 2005

Re: Need help on piston failure

Originally posted by Dhadley: LubeDude -- be careful about making statements that may mislead someone. That is obviously not a Wiseco piston. And the Wisecos do not need extra clearance compared to cast pistons.

Were these pistons posibly Wesco or Wysco, however you spell it? They seem to expand at a greater rate and need more piston to wall clearence. It has been posted here before that Wiseco pistons expand at a different rate. I did ask if they were as it wasnt obvious to me in the original post. Sorry if I missled anyone. It was a generic statement made by what I have heard here and other places, I guess things have changed.

reeldutch · Feb 17, 2005

Re: Need help on piston failure

the needle bearings are not so hard to install. you have to have a bushing of the exact diameter the wristpin is. I use a piece of plastick pipe. then place that in the piston and one by one slide in the needle bearings. youl figure it out it looks harder then it is. but you can replace them for the caged bearings. good luck reeldutch

Need help on piston failure

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