454 horizon exhaust manifold and riser question

N

Nikloai

New Member
Jul 26, 2019
2
Boat Info
2000 Sea Ray 340 Sundancer
Engines
454 Horizon with hurth V drive transmission
Hello guys. Im new to the site and would love to hear your input. I own a 2000 340 and ive had nothing but bad luck. Recently my engine failed after a piston made contact with an exhaust valve. My manifolds and risers are 2 years old and the heads were recently rebuilt. I bought a brand new 454 and now I want to make sure this never happens again. I believe water was dripping down from the gasket and eventual the valve seat rusted causing the valve to stick or it could have been the fact I had 1.5h no wake to get to my slip which I read causes condensation inside the exhaust. I have closed cooling through the block and raw water in the manifolds. I read you can get turbolator plates to prevent water injection. Who has done that and what part number did you use. Also I bought a brand new set of manifolds and risers made by mercruiser. The previous set up was made by sierra. I figured maybe parts were machined correctly. Do you retorque all the exhaust bolts after a good run? Anyone have torque specs for the exhaust risers? btw I have 3 inch spacers as well. Last but not least should I use a 4 hole gasket between the riser and spacer or use 2 hole gasket. I've read conflicting information.
 
Are these "dry joint" ones?
mufflers, what type or straight exaust?

The turbulators are used on dry joint systems
 
I have fiberglass mufflers with raw water going through the bottom of the manifolds and out the riser into the mufflers.
 
Nikloai said:
I have fiberglass mufflers with raw water going through the bottom of the manifolds and out the riser into the mufflers.
Click to expand...
Did you ever figure out the gaskets? I’m having the same issue with conflicting info. I have the same exhaust setup on my 5.7 horizons.
 
No you don't, he has a big block you have a small block with dry-joint exhaust.
What's your issue?
 
@scoflaw sorry to resurrect an old thread, was try to avoid flooding the forum. I have a 2002 310da with twin 5.7 horizons. The engine block is FWC (antifreeze) and the manifolds/3” risers/and elbows are RWC (seawater). The manifolds have 90 degree elbows on the bottom that connect to the heat exchanger. I just installed brand new exhaust and used full flow gaskets for everything per Mercruiser bulletin 99-10. I believe I need restrictor gaskets because now my starboard elbows on both motors are HOT to the touch. This was not the case before the new exhaust (yes the exhaust parts are correct). Old gaskets were aftermarket and too damaged to tell what they were but I recall at least some appearing to be restricted. Replaced the parts are preventative maintenance since I just bought the boat in September. Thanks for any input.
 
With a 2002 you might not have dry-joint, right around the period when Merc made the switch. Too bad you didn't do your homework before you replaced your exhaust, you could have easily done the dry conversion and included your manifolds into the closed part of the system.
Hot on the hose or when it's in the water? Post up your engine number, I'll take a look.
 
@scoflaw it’s not dry joint, I’ll do the conversion next time I replace everything. Had to do a lot of other work so we stuck with the wet joint for budget purposes. The starboard elbows are extremely hot to the touch port elbows are cool running on the garden hose. I did this with the old exhaust and no issue. Serial number for reference is 0L677308.
 
@scoflaw the boat is on the hard since it’s off season in NE so unfortunately I don’t know yet. A couple people on the 310da Facebook group said to use restrictor gaskets but everything I’ve read from Mercruiser says to use full flow above and below the 3” riser. Just don’t want to run it hot, I’d also rather do the work in my driveway and not in the water!
 
Your motor calls for identical gaskets 27-863726 above and below the riser. Don't sweat it I'm sure it will be fine in the water.
 
@scoflaw thanks for the quick replies. I’ll have to bring a heat laser gun when she’s back in the water.
 
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