7.5 Johnson 1958 AD12 Powerhead help

[SPK]

Once again I find myself in need of some expert advice with respect to the powerhead of this 7.5. Johnson.
My parts booklet shows in a diagram the first 6 parts in the gear case group page as being #1 303335 gasket, #2 303356 plate,
#3 303347 O-ring, #4 303391 Seal, #5 303357 spring, and #6 303327 washer.

These parts are all there on my motor and I have the powerhead removed to replace the powerhead gasket # 304314.

Could someone please enlighten me as to the purpose/use/function of the six parts mentioned above.
My parts appear to be in good shape yet I wonder if any should be replaced now that I am in this far.
What exactly do thes parts contribute to the proper function of this older motor? I don't know what they do.

Looking forward to hearing from you.
Thanks,
Sean.[SPK] Lindsay, Ont. Canada

 

[cajuncook1]

Re: 7.5 Johnson 1958 AD12 Powerhead help

Take a look at this link, it will enlighten you.

http://www.youtube.com/watch?v=SVOedhzPP7M&feature=channel

The combination of the parts that you mention, help form a seal against water intrusion into the power head. A lot of people neglect the parts you are mentioning and end up with a power head full of water and rust.

part 1 (303355) a definite change item

part 3 (303347) a definite change item [this part (o-ring) slides inside part 4]

part 4 (303391) carbon seal should be replaced if worn or damage


Remember part 7 (pin) has to be present to put pressure against part 6 (washer) in order for it apply pressure so that parts 6 to 1 form a seal. Part 7(pin) often gets damage or is not replaced so parts 6 through part 1 can't make a seal.

 

[cajuncook1]

Re: 7.5 Johnson 1958 AD12 Powerhead help

Here are a few links that may prove helpful to you if you have dive in the carburetor. Compliments of some very nice AOMCI members. God Bless them!!

It is not your exact model but suffices for the basic OMC 1950's carburetor.

Episode 19 http://www.youtube.com/watch?v=MwLrW51_uao&feature=mfu_in_order&list=UL

Episode 20 http://www.youtube.com/watch?v=GBsQ8rAYhOw&feature=mfu_in_order&list=UL

Episode 21 http://www.youtube.com/watch?v=Z8199RDZt5k&feature=mfu_in_order&list=UL

Episode 22 http://www.youtube.com/watch?v=4BKbY0pVmiQ&feature=mfu_in_order&list=UL

Episode 23 http://www.youtube.com/watch?v=PA4KG8_XysQ&feature=mfu_in_order&list=UL

Episode 24 http://www.youtube.com/watch?v=RgNy5RZrFGc&feature=mfu_in_order&list=UL

Episode 25 http://www.youtube.com/watch?v=4mvM-EYtBj0&feature=mfu_in_order&list=UL

Episode 26 http://www.youtube.com/watch?v=uIUo17JR6VA&feature=mfu_in_order&list=UL

Episode 27 http://www.youtube.com/watch?v=R38ji2kKsLA&feature=mfu_in_order&list=UL

Episode 28 http://www.youtube.com/watch?v=ad1g9bpuamw&feature=mfu_in_order&list=UL

 

[HighTrim]

Re: 7.5 Johnson 1958 AD12 Powerhead help

I will repeat it because I think it deserves a repeat....Frank has driven this into me.....seal is very important, replace it when replacing the powerhead and ensure it is installed correctly.

 

[SPK]

Re: 7.5 Johnson 1958 AD12 Powerhead help

Thanks so much for your advice. Are you referring specifically to the powerhead seal for replacement?

Is 303355 gasket made of anything special or is it just a cork gasket. I think I could just make that one if need be but my own looks great.
Sean.

 

[SPK]

Re: 7.5 Johnson 1958 AD12 Powerhead help

Thanks very much for sharing this info with me. The videos are really informative as well. So these old parts are still out there? Would dealers still stock them?
Thanks,
Sean.

 

[F_R]

Re: 7.5 Johnson 1958 AD12 Powerhead help

The seal parts are available from dealers. Actually, the 303347 and 303355 are available right here at iboats.