55hp Chrysler Am I Screwed?

[tater76]

Ok, so i have had my 16ft tri-hull 1973 Chrysler 55hp combo out 4 times this year already with no issues until today. The motor started to studder and lose power after WOT for approx 2 mins. I immediately checked the carb, took it apart cleaned it, replaced needle seat, installed new plugs, this is when my heart sunk. Pulled upper plug and found no gap, that's right it was smashed into the electrode. I immediately thought wrong plug, too long right? wrong! looked at the plug and found little balls of ? imbedded between isolator and plug housing, and there was a dent on one side of the arm over the electrode. I figure I have a melted ring right? but to get to shore I stuck a new plug in and all was fine for a while. I had power back, and no rough idle, then after another few mins of running WOT it did it again! Same smashed arm on the plug, but still ran on one cylinder ok. Put new plug in again, and never had another issue. What the heck do I do? leave it be and run it, or pull the head and check for broken melted parts?

 

[jaybirddog11]

Re: 55hp Chrysler Am I Screwed?

I would pull the head and take a look befor any more damage is done.

 

[Smokepole27]

Re: 55hp Chrysler Am I Screwed?

Sounds like something is starting to let go on a connecting rode? Im not too sure Im not familiar with the internals of those motors yet? The only way the piston could do that is if something is letting go.. You might have something in the cylinder that is bouncing around. Dont ask how but im sure it could happpen

 

[tater76]

Re: 55hp Chrysler Am I Screwed?

Ok, so I pulled both plugs last night, shined a light into the holes and saw what looks to me like tons of carbon build up. Think its possible to have some carbon chunks break off and get shoved into the spark plug? I will pull the head tonight, then I will let you all know how screwed I am. Thanks Guys

 

[Smokepole27]

Re: 55hp Chrysler Am I Screwed?

Im not too sure carbon will do that or get that big, when you take it apart turn the fly wheel or have someone turn it while you push on the piston and see if their is any play that will give you a good indication if you have a worn pin etc. There should be minimal play on them, they should be fairly tight!

 

[jaybirddog11]

Re: 55hp Chrysler Am I Screwed?

Wow, that would be alot of carbon, keep us posted.

 

[tater76]

Re: 55hp Chrysler Am I Screwed?

Thanks for the advice guys, I have to be honest though, I'm getting pretty nervous about what's waiting in that cylinder. Sounds like its gonna cost me a fortune? Is the motor worth the work, or should i scrap it if the piston/cylinder is shot?

 

[jerryjerry05]

Re: 55hp Chrysler Am I Screwed?

If it's just the carbon build up,then save it.
If it's the connecting rod,find another motor.J

 

[moparman]

Re: 55hp Chrysler Am I Screwed?

does this motor have two carbs? If so, sounds like one has run lean [ cylinder that melted plug , was it the top cylinder by chance???] That motor requires a lot of fuel[it's bigger brother has two pumps on it, these are the older chrysler motors we're talking about] I would look at the carbs real good and check the fuel pump and filter. Run a compression check and see if you hurt the motor. Keep us posted on what you find

 

[Frank Acampora]

Re: 55hp Chrysler Am I Screwed?

Oh, you are SO very screwed! LOL

It actually sounds like melted aluminum which would come from the piston crown. If it is a single carb 55, if the carb is slightly too lean, the bottom cylinder preferentially runs richer and the top piston usually has the damage. The melting is USUALLY right in the center at the plug electrode position. They will run for a significant amount of time before the piston perforates. IF the compression is still good, while there may be damage, the engine will still be serviceable. Simply richen the idle needle a bit and continue to run it. NOTE that on these engines a carb set too lean usually gives a BEAUTIFUL idle while a properly set one may have a slightly rough or erratic idle, It is what it is!

Replacing a piston at a later date is not that difficult or expensive since the cylinder liner may not be scored.

 

[tater76]

Re: 55hp Chrysler Am I Screwed?

Well, Frank has it! the top piston looks like freshly poured aluminum, but pitted. Lower piston is dark with crisp edges and no pitting. However, the pitting is on the edges and lower part of the dome. The ring is still good, and there is no scarring on the cylinder, thank god! Now, where do I go from here?

 

[tater76]

Re: 55hp Chrysler Am I Screwed?

I will post pics in just a few, you gotta see how right on he was!

 

[tater76]

Re: 55hp Chrysler Am I Screwed?

So here it is...the evidence. So, what do you guys think?

 

[notsunkyet]

Re: 55hp Chrysler Am I Screwed?

yea i think frank is right you could richen the mix and be running again... but ive always opted for the saying when in doubt replace.

 

[Smokepole27]

Re: 55hp Chrysler Am I Screwed?

Im sorry to hear that, but I bet itd be easy to find a used piston if you couldnt find a new. And if you cant let me know I just bought a head from a place in florida and am sure they have the size you need!

 

[tater76]

Re: 55hp Chrysler Am I Screwed?

Thanks for the support, so how hard is it to replace the piston? can it be done with basic hand tools, or am I going to need some specilty stuff? I am familiar with engines, just never replaced a piston. I know I should buy a manual, but it doesn't look all that complicated. Any suggestions?

 

[Frank Acampora]

Re: 55hp Chrysler Am I Screwed?

That damage is not too bad--mild detonation damage. I would make sure the carb is properly adjusted and run it until the winter, then replace the piston at your leisure.

3.1875 bore diameter --if the bore is not scored, a light honing and a standard sized replacement piston will suffice. Pistons are available from Wiseco and I am sure from Sierra for 80-120 bucks. Want to get sick? The first piston I replaced cost 12 bucks with two caged needle bearings included.

It is not a difficult job, the most difficult tasks will be removing the flywheel and actually getting the block off the leg--be aware that there is a seventh bolt either behind the idle relief cover plate or inside it.

As I said, My 1967 had two caged needle bearings carrying the wrist pin in the piston and the pin was press fit in the rod. Your 1973 should have loose needles in the rod small end and two keepers on the wrist pin.

Everything is hand tools except for pressing out the piston wrist pin. However, an impact screwdriver from Sears will make your life easier. A special tool is necessary to press in the pin so the needles are not squeezed between the spacers. If not used, the needles will not roll but slide over the wrist pin and rod small end bearing surfaces.

 

[tater76]

Re: 55hp Chrysler Am I Screwed?

Thanks Frank! that was exactly the advice I was looking for! I was afraid I would be on the dock all summer, now what manual do I buy that would show me how to adjust the carb to the right specs? or do you have any advice? I have a carb rebuild kit on the way, so I can start at square one.