Update on 65hp johnson: Help!

ShawnQ · Jan 22, 2003

Re: Update on 65hp johnson: Help!

alcan, What would allow water into the cylinder on these engines? The guy I bought it from said he thought water was getting into the cylinder, and was the cause as of the power loss..but he wasn't sure. He told me why he thought so, but I forgot. Don't be sorry, I'm not upset at all...I look at it as a good time to learn about outboard rebuilding basics. I've done a ford 302 and a chrysler 318 (non marine), but these marine 2strokes seem to be a whole new beast. Looks like it is time to learn! OK, so now what? Should I go ahead and start dissasembling the 'power head', or what I would call the short block? How do I know if the cylinder bore is still good or not? I can feel a few grooves in it, nothing really jagged or deep, MAYBE 1/64th(+or-) of an inch on the worst one, and I can barely feel the other grooves. The grooves go up and down in the cylinder, not around it. In an automotive engine, it would just need a 'hone'...but I'm not sure how these go. I'm assuming it may need a sleeve. Here are a few pictures of the piston, you can see the cylinder wall a little bit as well. You can see some scarring on the cylinder in this one..a little blurry, but still viewable:

Here is one from the other side, showing a little bit more scarring, not nearly as bad, I can barely feel it with my fingers:

Lastly, a picture pulled away a bit. I circled a little 'port' where there was an electrical sensor of some type installed. It went thru the head and head cover, any idea what it is?

If you have any idea as to what I should do next, I would appreciate it! I am considering rebuilding it all...or buying a new engine. Every engine I have found thus far has been too large for the boat I have. Thanks! Shawn

OBJ · Jan 22, 2003

Re: Update on 65hp johnson: Help!

Shawn...water can get in from the exhaust side of the cylinder or possibly the head gasket. Remove the head gasket and look at it carefully. If it has been leaking, you will see marks on the gasket around the metal edge. In extreme cases, the cylinder is cracked. If you decide to rebuild, strip the block first before pulling. It makes it a little easier to pull. When I rebuild a motor, all nuts and bolts go into a drawer marked where the go or in zip lock bags. Keeps parts and fasteners from getting mixed up. Do you have a manual for the engine? If not, you need to get one. Preferably an OEM manual. Don't know what the circled hole is for sure. Can't really tell from the pictures, are there any deep scores on the cylinder wall? How are the other cylinders looking? OBJim Nice to see ya' taking it so calmly.

Walker · Jan 23, 2003

Re: Update on 65hp johnson: Help!

I'm with OB, a piston ring let go. You're gonna need a new head if you rebuild. Here's another concern, there were a couple of year models of those 3 cylinders that had bad carbs that just didn't work well. If yours is one of those years you should look for new carbs too. I don't know offhand what years they were. Maybe OB, Clanton, or somebody else.

ShawnQ · Jan 23, 2003

Re: Update on 65hp johnson: Help!

OBJim... The other cylinders look like new other than the simple fact that there is a thin layer of carbon on the piston top. As for the depth of the scoring in the cylinder, I dont have any tools to measure it. I would say it is about 1/64th of an inch...MAYBE a little more, but it isn't very bad. Like I said, I've seen a lot worse in cars, and they were honed out. So, will I need to take the block and get it checked for cracks, or can I do that myself? As for the bolt/fastener organization...I usually put a number on top of them, and put numbers on the diagrams in the manual I am using...works for cars. I may do the ziplocs this time.. BTW, I do have a clymer manual, but it's for 1973andUp...but it is the same design I believe. I checked the head gasket, no signs of failure...this would cause it to overheat anyways, wouldn't it? The running temp was fine. Now, how do I check to see if the exhaust was leaking into the cylinder? Someone mentioned that they had a similiar problem one time...they said their powerpack was firing the cylinder at any given time (not at the right time though), and it caused all hell to break loose. Could my power pack be the culprit? I'm not worried about not having the ability to re-build it...I just dont know if I can diagnose the cause correctly. That's what you guys are for! BTW, it took me ~12 minutes to pull the head...very simple. Thanks! Shawn

jim dozier · Jan 23, 2003

Re: Update on 65hp johnson: Help!

Shawn, It looks to me like pieces of metal have been bouncing around in the combustion chamber (never a good thing). The picture of the cylinder head has definite angular and linear dents. Melting from pre-ignition alone wouldn't leave the angular and linear dents. Its hard to tell from the photo but it looks like parts of the exhaust side of the piston have come off. Can't really see. Are the rings still in the piston? If not pieces of piston or piston ring, I wonder if you sucked a reed or bolt or screw in from the bottom of the engine? Regardless, this baby is gonna have to come apart and see the machine shop before it runs right again. If it ever goes back together make sure the ignition timing is right when you run it.

ShawnQ · Jan 23, 2003

Re: Update on 65hp johnson: Help!

Walker, what's the best way to check if the cylinder is salvageable? Any guidelines I can go by? I'd like to rebuild it...but I'd like to find the cause of the problem first, and then I'd need to know if it IS rebuildable. Thanks again! Shawn

ShawnQ · Jan 23, 2003

Re: Update on 65hp johnson: Help!

JimD.. In the two pictures of the piston, you can see where a piece of the piston actually cracked off. It is in the top left of the picture. The piece is about 1/4 of the size of a penny. It cracked off from the ringland UP. Then, on the very bottom of the piston, closest to the floor...you can see the ring itself. A section of the piston ~2" was eaten off from the ringland UP. As for the ring...it's still in the piston. There is one or two areas where I can see some of it missing...but not as badly as the piston itself. It looks to me like the ring was in good shape until pieces of the piston started floating around in the cylinder... IF YOU NEED MORE DETAILED PICTURES OF ANYTHING, I CAN GET THEM...if it would help. Thanks. Shawn

jim dozier · Jan 23, 2003

Re: Update on 65hp johnson: Help!

Shawn, You answered my question. Apparently it is pieces of piston/and or ring that made the dents. One has to wonder what caused the piston to come apart in the first place. Pre-ignition and detonation have caused the death of a lot of engines. During your rebuild you might want to investigate the possible causes of the melted/cracked piston. Since the others are OK I assume it wasn't lubrication. My guess, and others would know more, is that you can overbore the cylinders (all three to make it balanced) and put in 3 new oversize pistons. The head is probably toast. The dents, even if you got a good seal, would cause terminal pre-igniton and start the issue all over again.

jim dozier · Jan 23, 2003

Re: Update on 65hp johnson: Help!

I just reread some of your earlier post about the cracked coils and arcing. If the bad cylinder was firing consistently at the wrong time that could have over a period of time killed that piston and cylinder.

ShawnQ · Jan 23, 2003

Re: Update on 65hp johnson: Help!

JimD... I wouldn't be suprised if it is coil related. However, Walker and I were talking ther other day and he asked me if I had the plug wires connected when the coils arced. I didn't. Therefore, the energy was looking for the area of least resistance to get to ground...and arced through the crack in the coil. However, I haven't had a chance to try it with the plug wires attached, so they may still be doing it. I know all about timing and pre-ignition, and what it can cause...I really don't know how to find out if it IS what caused it though, you know? I don't exactly know how to back track and see what was happening when the piston was being damaged. I guess I can look for water leaks into the cylinder, replace the coils, powerpack, and then make sure the timing is set,Check into the carb failure, and go from there. That is a lot of $$, for that I can buy a running engine...so I need to weigh my options first. Thanks for the ideas! Shawn

mike-evin-50hp · Jan 23, 2003

Re: Update on 65hp johnson: Help!

Shawn, I had the same motor with the same problem. Also new gaskets and parts by someone (I can share this later).Your pictures bring back memories. Bottom line - take the block to a good machine shop and they will tell you if they can clean it up. I had mine bored .030 on all 3, new pistons and rings, cleaned up the head (your head looks worse) and put it back together. Ran great and felt good doing it myself. The OMC manual and the parts book were a big help. I sure wish I had the help of all the pros on this site back in the late 80's. PS - I even had cracked coils like yours.

ShawnQ · Jan 23, 2003

Re: Update on 65hp johnson: Help!

Mike, If you dont mind, how much did you end up spending getting it re-done? What kind of specialty tools were required? Also, what caused yours to do this? I still haven't found the culprit on mine... I would love to rebuild this one...but I think I can get a new used outboard for less money. Thanks for any help. Shawn

alcan · Jan 23, 2003

Re: Update on 65hp johnson: Help!

Hi Shawn I would guess the previous owner knew all about the problems this motor has. You might not find where the water entered. I suspect there was a problem with the exhaust cover. but since the gaskets were replaced, it's going to be hard to tell. Another suspicion I have is, sence this motor dosen't have the stock powerhead or even the original horsepower. What I'm trying to say is the powerhead may not be compatable with the exhaust housing. This could also be a cause for water intrusion. Just because parts will bolt up dosen't mean they will work. The little hole you circled looks like it's where the heat sensor goes. If you consider and overhaul on this unit run down some parts catologs so you can identify your parts for compatabilty. I don't know what your goal is with this project. If it is messin around with an old motor just to see if you can fixit, then your good to go. And thats cool, there are a lot of us wierd tactile folks. If on the other hand you want to go boating,fishin,hunting. Scrap at darn thing and get an outboard motor. Remember you get what you pay for in this game.

ShawnQ · Jan 23, 2003

Re: Update on 65hp johnson: Help!

Alcan...I sure appreciate the help. The previous owner is a close friend of mine, and the rest of my family for that matter. He is not very mechanically inclined at all. I am absolutely positive that he didn't know exactly what was wrong with this engine...he would've told me, without a doubt. However, he did know that there was SOMETHING wrong with it, and I was also aware of it. He was selling it because he was tired of messing with it. He was the one who installed the current powerhead on the older casing... He bought the powerhead as it is, and has never been into it himself, but that's not to say the previous owner hasn't. The 2nd previous owner could've very well put a few of the wrong parts on it, I wouldn't be suprised. I am most likely only going to keep the boat for a year or two, at most, and intend to do a good bit of local lake fishing in it. With that said, I will most likely just get a different engine where I know the history behind it...instead of someone elses problems (which you risk either way, anyways). However, I am still thinking of rebuilding it. What kind of special tools are required in a 2stroke marine rebuilding process? What all should be replaced? If I do rebuild it, it will probably be just the bottom cylinder (a patch that will last me a year). I took it to a boat mechanic today, and he said it would need to go .030 over for sure. So, what will be needed? .030 Piston .030 Rings Wristpin? head gasket sealer what else? Thanks! Shawn

OBJ · Jan 23, 2003

Re: Update on 65hp johnson: Help!

Shawn...if it will help, when I get to the shop tomorrow, I'll get a list together for ya'. Post your email address and I'll get it to you. Least you'll know what's available and what ain't. OBJ

ShawnQ · Jan 23, 2003

Re: Update on 65hp johnson: Help!

OB Jim, that would help me a lot. You can email me at S_Queeney@hotmail.com Today I called a friend of mine who lives on the texas gulf coast, and has several connections in the boating business. I'm sure he can find me a reasonably priced outboard that will fill my needs. If not, I will rebuild the current one. However, I would still like a list. If nothing else, I will rebuild and sell the current one..get some of my money back at least, right? Take care, I appreciate it! Shawn

OBJ · Jan 23, 2003

Re: Update on 65hp johnson: Help!

OK shawn....I'll get it together first thing in the morning. OBJ

mike-evin-50hp · Jan 24, 2003

Re: Update on 65hp johnson: Help!

Shawn, If I recall, I spent about $700.00 rebuilding my power head. This did not include coils & carb rebuild. As far as the cause... I first had a bad head gasket and was sucking water. I took it to a mechanic who charged me ~ $1000.00 to rebuild the power head and carbs. However, he just honed the cylinders and put stock pistons back in. I don't think he actually measured the bore. After maybe 20 hours (with careful break-in) she was down again. This time I took it apart myself and the machine shop said the cylinders were way out of spec for stock pistons. The new pistons and rings had too much play and snapped a ring and thats what beats up the head and the exhaust ports and scores the walls (as you have seen). If you rebuild, check those ports on the cylinder walls. After boring, they may be to sharp and need to have the edge removed (Rotary tool). I think the only special tools I used was the flywheel puller and torque wrench. I had the guys at the machine shop help with installing wrist pins. As mentioned earlier, the OMC manual and parts book were a must have. Your parts list will give you a good idea about cost along with the machine shop.

jim dozier · Jan 24, 2003

Re: Update on 65hp johnson: Help!

Shawn, For my 2 cents if you elect to rebuild this engine I vote for all cylinders on the rebore and new pistons for all cylinders. Otherwise you'll be creating an unbalanced engine. I know you may want to just get it up an running but do the next owner a favor. The cost of a complete rebuild should be compared to a new/different outboard. I've no personal experience with just doing 1 cylinder on a rebore but I would bet it would have a lot of vibration in the crank and the engine wouldn't last long.

Walker · Jan 24, 2003

Re: Update on 65hp johnson: Help!

Shawn, before you start anything clean off the top of the pistons and look for some letters or numbers. You are looking for "STD.,.020,or .030.

Update on 65hp johnson: Help!

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