Ron V
04-27-2001, 04:57 PM
First, before I forget to mention it, Bill Gohr was the one who had told me some time back that the V-8 bolts were the thing to have for strength AND corrosion resistance. They are made of the 17-4 PH grade of stainless, hence their hefty price. Most places don't even carry these.
Alan, you are correct about the strengths. Anyone who would like to find out the truth about the strengths, and see how strong the 304 grades of stainless that hold your jackplates together really are, open a McMaster-Carr catalog or go to their website. STAINLESS IS NOT STRONG COMPARED TO PLAIN STEEL, GENERALLY SPEAKING. 304 stainless is not even half the tensile strength of Grade 8 steel. It is 2/3 the tensile strength of Grade 5. But it is the industry standard. It is also less brittle and has some give to it. You could go the hardware store, get a Grade 5 made in Bangaladesh, and it would likely still be stronger than the 304 (a type of 18-8 grade) stainless holding your jackplates together!
The standard transom bolt to the best of my knowledge is a 1/2" x 13 thread (coarse thread) 304 stainless. This is what most motors are held to transoms with. Obviously ultra-performance applications vary.
The company I work for has an in-house steel fabrication shop, and I also asked the guy who runs it about what he thought would be best for rigging my setback. Mind you they build things that people's workplace safety depends on. I described the application to him, including the horsepower (90; admittedly much less than most of you guys run), which he almost treated as irrelevant. I made a comment that I knew 18-8 stainless (304 falls into this category) to be weak compared to Grade 8 steel. He corrected me and told me that while it is not AS strong, it is NOT "weak". He was EMPHATIC in telling me that a 18-8 stainless bolt/nut from the local Ace Hardware was fine. His exact words were "You'll pull the ass end out of the boat before you'll break those bolts."
When my CMC ML-65 jackplate arrived in the mail, it was sent with 304 stainless bolts. And the 300 horsepower rating sticker is right on the side of it. Now, the side bolts that hold the plate itself together are 3/4" instead of 1/2". And I can see that, since they are subjected to shearing instead of pulling. The side bolts that broke on Wicky's boat, if they were the grade that has been stated on this board, were, to the best of my knowledge, very little if any weaker than a 304. Grade 2 has a tensile strength of 60,000 psi. 304 stainless, or 18-8, is 70,000. Grade 5 is 105,000. Grade 8 is 150,000. Grade 3 or 4, I am not sure of, but I'd guess them to be close to or maybe even stronger than 304. Unless they are corroded....
Not trying to talk loud here because I know that my hardware store bolts could fail, but I think Alan hit the nail on the head ont his one with his comment on the strengths. All of you can take this for what it's worth. I am for sure no expert.
Alan, you are correct about the strengths. Anyone who would like to find out the truth about the strengths, and see how strong the 304 grades of stainless that hold your jackplates together really are, open a McMaster-Carr catalog or go to their website. STAINLESS IS NOT STRONG COMPARED TO PLAIN STEEL, GENERALLY SPEAKING. 304 stainless is not even half the tensile strength of Grade 8 steel. It is 2/3 the tensile strength of Grade 5. But it is the industry standard. It is also less brittle and has some give to it. You could go the hardware store, get a Grade 5 made in Bangaladesh, and it would likely still be stronger than the 304 (a type of 18-8 grade) stainless holding your jackplates together!
The standard transom bolt to the best of my knowledge is a 1/2" x 13 thread (coarse thread) 304 stainless. This is what most motors are held to transoms with. Obviously ultra-performance applications vary.
The company I work for has an in-house steel fabrication shop, and I also asked the guy who runs it about what he thought would be best for rigging my setback. Mind you they build things that people's workplace safety depends on. I described the application to him, including the horsepower (90; admittedly much less than most of you guys run), which he almost treated as irrelevant. I made a comment that I knew 18-8 stainless (304 falls into this category) to be weak compared to Grade 8 steel. He corrected me and told me that while it is not AS strong, it is NOT "weak". He was EMPHATIC in telling me that a 18-8 stainless bolt/nut from the local Ace Hardware was fine. His exact words were "You'll pull the ass end out of the boat before you'll break those bolts."
When my CMC ML-65 jackplate arrived in the mail, it was sent with 304 stainless bolts. And the 300 horsepower rating sticker is right on the side of it. Now, the side bolts that hold the plate itself together are 3/4" instead of 1/2". And I can see that, since they are subjected to shearing instead of pulling. The side bolts that broke on Wicky's boat, if they were the grade that has been stated on this board, were, to the best of my knowledge, very little if any weaker than a 304. Grade 2 has a tensile strength of 60,000 psi. 304 stainless, or 18-8, is 70,000. Grade 5 is 105,000. Grade 8 is 150,000. Grade 3 or 4, I am not sure of, but I'd guess them to be close to or maybe even stronger than 304. Unless they are corroded....
Not trying to talk loud here because I know that my hardware store bolts could fail, but I think Alan hit the nail on the head ont his one with his comment on the strengths. All of you can take this for what it's worth. I am for sure no expert.