6hp Johnson 1968 fuel pump mounting bolts - wrong ones fitted!

[Swell]

Can anyone let me know what the correct bolt / screw size is for the 2 bolts which fix the fuel pump to the powerhead?

It looks like a previous owner has fitted bolts with the wrong thread and too short. Thankfully just the first 3mm or so of the thread on the powerhead has stripped and there's plenty left further in. So I want to run a tap down just to clear those few stripped threads. I don't think it needs a helicoil.

The part no. is 0309654 (SCREW, Fuel pump mount) but I can't find the length, diameter & thread type anywhere. The engine is a CDL-25c.

Any help would be much appreciated!

 

[F_R]

Re: 6hp Johnson 1968 fuel pump mounting bolts - wrong ones fitted!

#10-24 threads. Sorry I don't know the length offhand

 

[Swell]

Re: 6hp Johnson 1968 fuel pump mounting bolts - wrong ones fitted!

I'm in the UK & only really familiar with metric sizes so apologies if these seem like dumb questions!

Is that UNC or UNF?

What's the diameter in fractions of an inch?

Or is that a standard thread size?

Edit - I realise now that's a UNC thread. What would be the associated bolt diameter?

 

[Silvertip]

Re: 6hp Johnson 1968 fuel pump mounting bolts - wrong ones fitted!

This chart should help you.


http://www.engineershandbook.com/Tables/threadlimits.htm

 

[Swell]

Re: 6hp Johnson 1968 fuel pump mounting bolts - wrong ones fitted!

Cheers for that. I'm still confused though - there's a lot of info on the table and it looks like there are 2 versions - 2A & 3A. Is 10-24 a bolt size? e.g. could I order a 10-24 bolt x 1" long?

 

[Vic.S]

Re: 6hp Johnson 1968 fuel pump mounting bolts - wrong ones fitted!

#10-24 means size 10, 24 tpi which means that it is a UNC thread with an OD of 0.1900" and a 60? angle.

goodness knows where you will find them in the UK .. not just two anyway .. other than as the OMC part number 0309654.

Someone like Oakley Marine, www.outboards-direct.co.uk in Brighton or Willsmarine, www.willsmarine.co.uk in Devon should be able to supply them ( Try Oakley first but remember they may be recovering from the LIBS for a few days)

Alternatively try 3/16" Whitworth. That's very slightly smaller at 0.1875" OD but it has the same thread pitch at 24 tpi although Whitworth threads are 55?

The other alternative is to drill and tap to a larger size.

I don't know if you could make them M6 or 1/4" Whit, but then you'll also need to drill out the holes in the pump. If you re-tap them you'll need a plug tap

 

[Swell]

Re: 6hp Johnson 1968 fuel pump mounting bolts - wrong ones fitted!

Many many thanks for that! I get it now. There's a local supplier in Hove called the Nut & Bolt Shop and if anyone has them they will. Their website for anyone who's interested is http://www.namrick.co.uk/. Or just order the OMC part.

Otherwise I'll drill and tap for the nearest metric size. Not sure if I'd get away with an M5. I'll update when I've done the job.

 

[James R]

Re: 6hp Johnson 1968 fuel pump mounting bolts - wrong ones fitted!

These bolts should still be available through your OMC dealership. You can find the part numbers on www.boats.net.
Ex Limey here.

 

[Vic.S]

Re: 6hp Johnson 1968 fuel pump mounting bolts - wrong ones fitted!

You can find the part numbers on www.boats.net.

On in my post, #6, a bit up the page