Manifold torque specs

Will 55

Will 55

New Member
Nov 3, 2018
25
Boat Info
'87 230 Weekender
Engines
5.7 L Alpha 1
quadrajet 4 barrel

Tow with: Toyota Sequoia 5.7L
I did my first manifold and riser replacement on my 5.7 Merc 260 and followed the torque specs precisely, bought a torque wrench specifically for the job.

The other side I paid a mechanic to do and change the starter at the same time. I asked him how many lbs he torqued the manifold and he was taken aback an got upset. He said, "Are you kidding me! It's on and it's not going to fall off." I asked his assistant who did the work and he just made up a # and said, "oh, about 90". I can't recall the exact torque specs but I think it was something like 35 or 45 on both manifold and riser. How critical is this? I guess it's better too tight than too lose. Being an '87 freshwater boat, this was the first change out, and will certainly be the last time this will ever need to be done. Anyone have the proper torque specs for manifold and riser on a 86-87 Merc 260?
 
Will 55 said:
I did my first manifold and riser replacement on my 5.7 Merc 260 and followed the torque specs precisely, bought a torque wrench specifically for the job.

The other side I paid a mechanic to do and change the starter at the same time. I asked him how many lbs he torqued the manifold and he was taken aback an got upset. He said, "Are you kidding me! It's on and it's not going to fall off." I asked his assistant who did the work and he just made up a # and said, "oh, about 90". I can't recall the exact torque specs but I think it was something like 35 or 45 on both manifold and riser. How critical is this? I guess it's better too tight than too lose. Being an '87 freshwater boat, this was the first change out, and will certainly be the last time this will ever need to be done. Anyone have the proper torque specs for manifold and riser on a 86-87 Merc 260?
Click to expand...

https://www.perfprotech.com/blog/tech-specs/mercruiser-v6v8-fastener-torques
 
I wouldn't trust them to change tricycle tires if that's how they reacted.
 
Will 55 said:
I did my first manifold and riser replacement on my 5.7 Merc 260 and followed the torque specs precisely, bought a torque wrench specifically for the job.

The other side I paid a mechanic to do and change the starter at the same time. I asked him how many lbs he torqued the manifold and he was taken aback an got upset. He said, "Are you kidding me! It's on and it's not going to fall off." I asked his assistant who did the work and he just made up a # and said, "oh, about 90". I can't recall the exact torque specs but I think it was something like 35 or 45 on both manifold and riser. How critical is this? I guess it's better too tight than too lose. Being an '87 freshwater boat, this was the first change out, and will certainly be the last time this will ever need to be done. Anyone have the proper torque specs for manifold and riser on a 86-87 Merc 260?
Click to expand...

You do not want to over torque bolts. Period. There is no such thing as "better too tight than too loose".

Manifolds are typically cast iron. Over torquing can cause stress risers in the metal. Also, over torquing can stretch the bolts. Torque and follow the pattern provided by the manufacturer.
 
Off the top of my head I was like 35.... as an electrician I learned the importance of proper torque.... over tightening is just as bad as not tight enough IMO

Will 55 said:
I did my first manifold and riser replacement on my 5.7 Merc 260 and followed the torque specs precisely, bought a torque wrench specifically for the job.

The other side I paid a mechanic to do and change the starter at the same time. I asked him how many lbs he torqued the manifold and he was taken aback an got upset. He said, "Are you kidding me! It's on and it's not going to fall off." I asked his assistant who did the work and he just made up a # and said, "oh, about 90". I can't recall the exact torque specs but I think it was something like 35 or 45 on both manifold and riser. How critical is this? I guess it's better too tight than too lose. Being an '87 freshwater boat, this was the first change out, and will certainly be the last time this will ever need to be done. Anyone have the proper torque specs for manifold and riser on a 86-87 Merc 260?
Click to expand...
 
What a completely unprofessional reaction. Red flags for that crew.
You should go back and check those bolts with your new torque wrench then check them all after running for about ten hours or so. With some thing as important as those manifolds, bolt tension should not be left to Laurel and Hardy.
 
DWABoat said:
What a completely unprofessional reaction. Red flags for that crew.
You should go back and check those bolts with your new torque wrench then check them all after running for about ten hours or so. With some thing as important as those manifolds, bolt tension should not be left to Laurel and Hardy.
Click to expand...


Thanks, I will check the torque on those bolts when the engine is warm and adjust if necessary. Thanks everyone for the input.
 
I found the revised Merc Service Bulletin that I used originally for my manifold and riser. It is 33 ft/lbs
 

Attachments

  • Mercruiser Exhaust Manifold torque.pdf
    20.9 KB · Views: 1,689
Will 55 said:
Thanks, I will check the torque on those bolts when the engine is warm and adjust if necessary. Thanks everyone for the input.
Click to expand...
To check them, generally speaking, I'd loosen them one at a time and retorque to spec. Just checking them won't tell you if they're over torqued.
 
Will 55 said:
I found the revised Merc Service Bulletin that I used originally for my manifold and riser. It is 33 ft/lbs
Click to expand...

The Service Bulletin calls out the new, 33 lb-ft value when installing exhaust elbows or risers onto exhaust manifolds. Not for the manifold to head fasteners. For the manifold to head fasteners you should stay with the original specifications, 20 lb-ft.
 
I am wondering if they torqued them really tight then you loosen them will the gasket be crushed.
 
This is a perfect story of why the only person that works on my engines is..........me.
I can't find a "professional" that give more of a shiz than I do.
 
You must log in or register to reply here.

Forum statistics

Threads
113,154
Messages
1,427,384
Members
61,060
Latest member
Danileo
Back
Top