Re: Replacing rust exhaust bolts
If those are the bolts holding the exhaust cover, gasket and stainless plate assembly to the block and if your engine is still the 85 HP, then they are not stock--they are way too long and the two on the left are too thick too. They look like head bolts. Perhaps the P.O. drilled, tapped, and replaced them? Does the block show any signs of snapped bolts that were drilled out?
As far as replacing them, you can replace all with stainless bolts BUT you must used anti-seize or silicone RTV. If you don't, aluminum in the block and stainless in contact will set up a galvanic reaction and the bolts will quickly corrode into place. Even with minute amounts of moisture and fresh water use. I routinely replace all fasteners EXCEPT head bolts with stainless. You can buy stainless bolts in Lowes or Home Depot but a better choice would be to find a Fastenal. In any case, it will be expensive.
If we are indeed looking at head bolts, these really need to be replaced with grade 8 bolts. It came from the manufacturer that way for a reason and I have never seen a reason to try and replace them with stainless. Grade 8 have six "hash" marks on the head--six lines, usually one at eac point. Some will have a circle and lines.
Those bolts do not show enough damage to be unusable. You could reuse them as is or give them a light sanding first. To prevent further rust, you can coat the entire bolt with anti-seize--silver colored nickel base. Other mixtures, especially copper will corrode.
Even though torque specifications are for dry bolts, the head bolts at 225 inch pounds will not be too tight and will not strip with anti-seize lubricating them.
Same thing for 70 inch pounds on 1/4 X 20 exhaust cover bolts.
