Are M10 bolts for a BF150 would be OK?

[Iskander-M]

Hi guys,

Can please anyone tell me if the M10 would suffice to fit the BF150? The Honda fitting instructions suggest 4x M12 bolts but I need to use the 10mm. The reason is the that the engine sits on a stainless Gil Marine bracket which creates an electrolysis and I had some corrosion issues.

The idea now is to fit the engine with an acrylic shield 1-2mm between the bracket and the engine and use the M10 bolts with shoulder washers so there is absolutely no contact between stainless bracket and aluminium engine parts. That will be the 12mm finished diameter to fit in the engine’s holes.

Checking the stainless bolts shear resistance I find that a 10mm bolt A2 70 would hold a 1.8 tonnes so 4 of them totalising 7.2 tons so looks not bad for a 225kg engine.

Any suggestions or opinions? Thanks in advance.

 

[dingbat]

Hi guys,

Can please anyone tell me if the M10 would suffice to fit the BF150? The Honda fitting instructions suggest 4x M12 bolts but I need to use the 10mm. The reason is the that the engine sits on a stainless Gil Marine bracket which creates an electrolysis and I had some corrosion issues.

The idea now is to fit the engine with an acrylic shield 1-2mm between the bracket and the engine and use the M10 bolts with shoulder washers so there is absolutely no contact between stainless bracket and aluminium engine parts. That will be the 12mm finished diameter to fit in the engine’s holes.

Checking the stainless bolts shear resistance I find that a 10mm bolt A2 70 would hold a 1.8 tonnes so 4 of them totalising 7.2 tons so looks not bad for a 225kg engine.

Any suggestions or opinions? Thanks in advance.

Really bad idea all the way around.

Need to read up on the mechanisms and remediation of Bimetal corrosion and applied mechanics.

How much shear does a 225 kg load at 6 g generate?

Hint, stainless and aluminum are both classes of materials of varying compositions. While stainless Y and aluminum B, might get alone well at the molecular level, Stainless Z and aluminum A when combined may be catastrophic.

Lots of Gil brackets around without corrosion issues. You need to find the cause of the problem and address it.

 

[Sea Rider]

Check that all anodes have sufficient tall material for proper degradation, are immaculate clean and make sure that the lower leg and swivel bracket are well grounded between them if that helps to lessen or cancels the bracket's corrosion issue..

Happy Boating

 

[Iskander-M]

Thanks for your replies gents, but there is not much I can do about corrosion issues except shielding the metals and change the anodes

How much shear does a 225 kg load at 6 g generate?

I don't that much, it's not a F1 but a 1.8T fisher cruising 20 topping 28

Need to read up on the mechanisms and remediation of Bimetal corrosion and applied mechanics.

I boat in this area for 7 years and galvanic corrosion issues in Thames are quite common. On our club's moorings the corrosion varies from one side to another one where the bed changes from mud to clay. It is normal to replace the double shaft anodes on inboards twice a year.

Lots of Gil brackets around without corrosion issues. You need to find the cause of the problem and address it.

Lots of powder coated alu Gil or Stainless Marine or anything else, but not much of stainless. From my research on my bracket I know that Gill was the first serious manufacturer of the stainless brackets and switched to alu after all the outboards manufacturers wrote in they warranties that these regarding corrosion are automatically voided if mounted on Gil stainless bracket.

This is to say that have gone through the possible problems of the corrosion issues which are almost unavoidable due to my set up and local specificity, I'm just asking if anyone had experience with M10 bolts on a similar engine instead of M12.

On this forum I saw someone using hot dip galvanized bolts instead of SS, would it be the option?

 

[Scott Danforth]

If the bolts were a complete special alloy that most likely doesnt exist, then maybe

if not, follow the OEM recommendation on size, and isolate the shank of the bolts with garolite tube

 

[Iskander-M]

Thanks for advice about the Caroline tube, will give it a try!

Cheers