MAc 45 wrist pin failure

[tnrcboatracer]

I was working with my SP40 today and trying to finishe the breakin of my AB prepped MAC45. The boat seemed to be responding well to the new turn fin and I was working on handling with prop selection and strut depth. I had just finished a couple of laps with the latest setup when the motor seemed to load up and die withing 100ft. I thought that maybe I had run out of fuel since I had been in and out several times with out refueling. Anyhow, I removed the plug and blew out the motor, only to find many small aluminum shavings on hte bright blue head cap. NOT GOOD. Time to pack it up and check it out at home. After removing the engine from the hull, my finger snagged on something sharp on hte bottom; MORE NOT GOOD! I pulled the rotor housing ogff, and found thaqt something hard had been wedged between the big end of the rod and the case. Well, time to takes it home for major tear down.

Top make a long story short, I found that something of significant size and hard went through the engine. Major damage to the head button and piston crown, and when I removed the wrist pin to find it in 2 pieces. It failed right at the edge of the pin boss. Once I lined up the fracture surfaces, I found that a piece about 1/16' x 1/32" was missing. Well now I know what went through the engine. I also found that the rod was also now bent. Basically the engine is now trash, and it wasn't even broken in.

I was wondering if anyone else has had wrist pin failures on the MAC 45. I have a couple more MAC 45's and am concerned about a defect. MY engine was freworked by andy himself ans is dated 10/02. It has been oiled and stored as a backup since new. I am a little diappointed since I feel that this was probably a manufacturer's defect, but any hope of warranty is probably gone due to the situation with MAC, and the fact that motor is 4 years old (though unrun). I will give a call and see if I will be surprised, but I don't hold much hope. Any one else have this failure mode?

I have pics that I'll try to post shortly.

 

[ALLAN YUEN]

I was working with my SP40 today and trying to finishe the breakin of my AB prepped MAC45. The boat seemed to be responding well to the new turn fin and I was working on handling with prop selection and strut depth. I had just finished a couple of laps with the latest setup when the motor seemed to load up and die withing 100ft. I thought that maybe I had run out of fuel since I had been in and out several times with out refueling. Anyhow, I removed the plug and blew out the motor, only to find many small aluminum shavings on hte bright blue head cap. NOT GOOD. Time to pack it up and check it out at home. After removing the engine from the hull, my finger snagged on something sharp on hte bottom; MORE NOT GOOD! I pulled the rotor housing ogff, and found thaqt something hard had been wedged between the big end of the rod and the case. Well, time to takes it home for major tear down.

Top make a long story short, I found that something of significant size and hard went through the engine. Major damage to the head button and piston crown, and when I removed the wrist pin to find it in 2 pieces. It failed right at the edge of the pin boss. Once I lined up the fracture surfaces, I found that a piece about 1/16' x 1/32" was missing. Well now I know what went through the engine. I also found that the rod was also now bent. Basically the engine is now trash, and it wasn't even broken in.

I was wondering if anyone else has had wrist pin failures on the MAC 45. I have a couple more MAC 45's and am concerned about a defect. MY engine was freworked by andy himself ans is dated 10/02. It has been oiled and stored as a backup since new. I am a little diappointed since I feel that this was probably a manufacturer's defect, but any hope of warranty is probably gone due to the situation with MAC, and the fact that motor is 4 years old (though unrun). I will give a call and see if I will be surprised, but I don't hold much hope. Any one else have this failure mode?

I have pics that I'll try to post shortly.

h34r: I had a problem with MAC 21 before piston was cracked so I send proof picture to CMDI Andy Brown and he gave me discount price for new P/S , wrist pin, inerst head and conrod That's good service business

 

[Duck899]

I would be curious to know what the bearings look like in this engine? Have you removed them to see if there are parts of the cages missing? If the engine had sat for 4 years even oiled, there is the possibility of corrosion in the cages causing failure in this area thereby slamming into the head and button which puts undue stress on the wristpin and bosses in the piston. Looks like the engine was running with bits and pieces of shrapnel between the piston and head button just before the wristpin let go. There had to be heat created to damage the piston and head button in those pictures as shown. Are those plier marks on the head button as well? I'm no engine guru but I've seen this sort of thing before and I'm sure some of the engine experts will chime in. I would talk to Andy as you said and see what he can do.....

Sorry about your engine, they are really nice engines, I ran one in my sport 40 for a couple of years and it was a rocket with great reliability.......

Good Luck....

 

[tnrcboatracer]

Thanks for your comments. good observation. Yes, there are plier marks on the button, because that was the only way I could get it out of the sleeve. Some of the impacts actually expanded the head button radially, wedging it into the sleeve. The bearings are smooth, but I have not yet pulled the crank out. The rear bearing looks fine, it has a polyamide cage that appears to be intact. The engine has been run about 1-2 sessions per year over the last 2 years. I flush it at the beginning and end of the season, whether it has been run, or not. The piston fit was exceptional before the failure. The damage appears to have been caused by the piece that is missing from the wrist pin. They appear to be impact craters, no melting or major heat. If it failed at full RPM, I think it could have caused this. I briefly mentioned it in my first post, but I only found the issue when small aluminum flakes were found on the head cap when I blew it out. I didn't find the failed wrist pin until I tore it down after I returned home. It seemed to turn over smooth at the pond.

Overall, I am very happy with my MAC engines. I have 12 0f them (11 now) in all displacements, and this is my first failure in 6 years.