Stuck a piston

[blueskyracer]

Our weekend finally went better this time.. We actually got to race but it was not without a cost.. The weekend did not start out good.. After a lot of break in and half throttle laps I started to open the motor up and it was taking off like a raped ape and I got to about 3/4 throttle and then I was on my nose with a terrible silence. I must say I hate that sudden stop.. Took the engine apart last night and #3 stuck..

Put on a backup John Myers motor and had no more problems with the boat..It was a wee bit on the rich side but I decided that was safe for now.. Also got to run the Euro boat and it got on plane instantly and now it turns without spinning out.. I guess I have to use it since I lost my ride to my daughter so I will spend more time sorting it out

I have one picture of the boat returning to the pits.. Will post later after the wife gets done with photo bucket

[form-e one]

soo many possibilities... cooling where it comes in how it routed and your out locations,, and sizes,,, oil mix ratio.. and piston wall clearance...the one i built for kenny hasent missed a beat.. and pegs the water guage with komato foot..

[blueskyracer]

The cylinder cleaned up with a little acid and light hone job

[seanp3]

Boy! That's what mine look like when overheated. I was watching you run when this happened and 99% sure you were watering

[Danny Pigott]

Piston

Mike I will send you a pm, if I forget let me know

[ZUL8TR]

wrist pin clips

The cylinder cleaned up with a little acid and light hone job

On reassembly I would rotate those wrist pin clips with the tang at the bottom of the hole.

[blueskyracer]

On reassembly I would rotate those wrist pin clips with the tang at the bottom of the hole.

I will do that and I plan to double check ring gap..Got to get this done in time for a race the 7 and 8 or else I will be just a pit witch

[ZUL8TR]

ring gap

I will do that and I plan to double check ring gap..Got to get this done in time for a race the 7 and 8 or else I will be just a pit witch

What gap are you using?

[Dave M]

Check Bore

When boring a blind hole, such as the Merc 44, extra care has to be taken to get the bore all the way to the head. if it does not, you will stick many pistons. Honing does not accomplish this either. A special hone might do it, but not your standard Sunnen Hone a lot of us use. It is critical to make sure the bore is straight all the way down, and no taper exists. If not, the rings will get pinched, and do pretty much what your pic shows. Just something to check before re-assembly. Better to make sure while apart than to wonder why the same piston burned again.

[jeff55v]

Every time I overheated a Merc, (many times) the rings always scored and stuck on the exhaust side of the piston at the exhaust ports. Never at the top or bottom of the piston as it sits in the block.

[blueskyracer]

Another great weekend.. Did it again on cylinder number 2 this time.. Also did in two more motors on two different boats.. At least the season is over

[JBM]

I fought the same thing once. I had to increase the clearance between the piston and the rod. I just ground off a little of the pin boss inside of the piston.

[pops67g]

Seems silly to ask but.....

when you said the same thing happened to two other motors it sounds likely that the same mistake applies to all of them. What oil mix are you using? The only time I have ever had a piston look like the one in the picture is when the power head bolts loosened up and starved the top two cylinders for water and then the damage was spread around the exhaust side of the piston. Oil is cheaper than parts and I regularly run an 8:1 ratio in my stock and mod 4-bangers and have never had a hint of a failure. That's 26 years alone on my 44XS.

[DiGia54D]

Mike, Sent a PM

[blueskyracer]

when you said the same thing happened to two other motors it sounds likely that the same mistake applies to all of them. What oil mix are you using? The only time I have ever had a piston look like the one in the picture is when the power head bolts loosened up and starved the top two cylinders for water and then the damage was spread around the exhaust side of the piston. Oil is cheaper than parts and I regularly run an 8:1 ratio in my stock and mod 4-bangers and have never had a hint of a failure. That's 26 years alone on my 44XS.

Stuck the same motor only on a different piston.. Another motor just shut off and we don't know why.. Maybe fuel pump and the other motor was either to lean or got over heated.. I am running 8:1 oil