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I plan to replace my risers before I go in in the spring. The new ones that I bought (Barr # MC 20-72963) came with bolts to secure them to the manifold. Should I be using studs instead? When I bought the boat the previous owner's mechanic had used some of each. When my yard replaced the risers four years ago, they used bolts.

This is for 454s with log manifolds.

In some applications they use both bolts and studs because of clearance issues. This is not specifically for 454s but more in general. The inner lower riser bolt on my turbos uses a nut on a stud as opposed to a bolt. Also can help hold the heavy thing in place...

I dont think it is like using studs on a head where you are looking for strength but more a convenience thing (I could be wrong on that but risers are not under pressure like heads)

6 of 1 or a half dozen of the other...it makes no difference aside from preference...not for the exhaust manifold, just use grade 8 hardware,

When I did mine on the crusaders on my 31 there was a mix of studs and bolts. On my shamrock Pleasure craft I had to make studs just to hang everything then replace with bolts! I might have made a few studs to leave can’t Remember definitely second what Carl said about grade 8 minimum.

I found a parts list for my engines on-line (https://www.perfprotech.com/mercury-mar ... ?model=814 ) and ordered the studs and corresponding nuts based on the part numbers that they listed. The nuts turned out to be flanged with serrations on the flanges (see the link below). I assume that this means that they are to be used without lock washers. Does this make sense? The risers came with bolts, but it looks to me like it would be easier to get the gaskets and blanking plates to line up and stay in position if I used the studs. When I got my boat the risers were held on with a mix of studs and bolts. The boat yard used bolts when they did my risers four years ago.

Any suggestions welcome.

http://www.ipernity.com/doc/307687/51224540

The larger diameter of the Flange is to disperse the force of the nut, similar to what a washer does. The serrations are to enhance vibrations resistance similar to a lock washer.

Grade 8 hardware whether bolts or studs with washers and lock washers OR use the serrated flanged hardware. Whatever you choose...it's not a bad idea to run the boat a few hours then go back and re-torque/Snug up again. Vibrations and heat cycles get things to settle in...often nothing changes, sometimes a quarter turn here and there.


My suggestion is to stick with quality grade 8 hardware and use whichever is available and easiest to assemble.....and down the road disassemble. Mix and match or keep all the same, no real difference to speak of.

I used studs on my 454s with log manifolds in the Anna E. It made putting the manifolds on a lot easier.

Studs if you have room. Less chance of wringing them off later down the road.

I ended up using the studs and flanged nuts so that it would be easier to keep the gaskets and the blanking plate in place. One of the 90-degree elbows on my port engine had a 1" chunk missing from the lip. This made it impossible to slide the hose from the riser far enough on to get a decent seal, so I ended up replacing the elbows with a pair of Barr Marine cast iron 90-degree elbows. The ones I got adapted the 3" hose from the riser to my existing 3 1/2" hose downstream. I replaced both elbows so that I would not have unbalanced backpressure on the port engine.

The yard put the boat in on Wednesday and the supervisor was good enough to let her sit in the slings while we started both engines and verified that I had done the job correctly. She ran well on the short trip from the yard in Sayville to my slip in Great River.

Thanks for all of the suggestions and encouragement.

pschauss wrote: ↑Apr 22nd, '22, 20:18 She ran well on the short trip from the yard in Sayville to my slip in Great River.

We really do need a like button!
Hope you have a great season.
Stephan