3GM30 Cranksft Nut Size

[hunter healer]

Hello out there me again trying to find the crankshaft front pulley nut and thread size for my 84 Hunter with 3GM30. Someone stripped the nut and I had to split it off! The threads look healthy but there is a burr or two around and I want to run a thread chaser over the threads before I run the new nut down on the belt pulley. Anyone know what thread and where I can get a chaser?
Many thanks for all your help

 

[kloudie1]

Parts book says it is an M18 but doesn't give the thread pitch.. pitch could be 1.5 (most probable) or it could be 2.5 (fine) or it could be something else.
A fastener place like Fastenal or Grainger probably can supply you with one and chaser

 

[hunter healer]

Thank you, do they use a washer behind the nut?

 

[kloudie1]

No washer.. The nut is probably a "Heavy Nut" meaning it is a bigger body than a standard nut..
Yanmar part # is 26776-180002. they are about $2 from Yanmar

 

[hunter healer]

The one I bought from Yanmar was less than $2.00 and average thickness as was the original not heavy like the prop nut

 

[hunter healer]

I’ll check the part number I have the orig packaging thank you

 

[kloudie1]

I had wrong part #.. It is correct now..

 

[hunter healer]

I ordered the thread chaser from fastenal today. Any recommendations how I chase the threads / use the chaser! Oil the crank shaft allot do in 1/ 4 turn and back off and then clean the threads before going on again???

 

[kloudie1]

Yup.. Very carefully

 

[hunter healer]

Thanks for the confirmation! I have never chased threads on something this expensive

 

[Charles Erwin]

Consider a thread file. Cheap and useful for other (inevitable) thread restores. Just need one for 8 pitches.

Charles

 

[hunter healer]

I was successful with the thread chaser until I tried the new nut, it went on a little wobbly yanmar part #26776-180002 now what

 

[hunter healer]

I guess I believe the thread chaser for the size 18-150, if the nut was mis packaged could the nut have a different pitch? I’m wondering if I should purchase a few different pitches to try them out. I don’t trust it holding the pulley fast

 

[jibes138]

If it was the wrong pitch it wouldn't go on more than one turn, if that, and jam up. What are you using that you are calling a "thread chaser?" Is it a die made for cutting threads? Did you cross thread it when you "chased the threads?" For the nut to be "wobbly" yet still screw on it means the pitch diameter of the thread is too small on the shaft or too big on the nut. Try a standard nut from fastenal, home depot, Lowes, or any other hardware store with the thread size from the die you used and see if it fits tight. It is possible but unlikely Yanmar sold you a bad nut, Checking with another one will only cost a small amount to make sure.