distance for check valve in exhaust?

[albinalaska]

good morning,

i’ve posted about this general topic a few times but am hoping for some more guidance. i’m looking at replacing my transom exhaust port, check valves and exhaust hose on my vessel.

is there any literature in the ABYC or other governing bodies that dictate the distance between the transom exhaust outflow and the engine that i could/should place a check valve?

in other words: how far back the check valve can go between the engine and the back of the boat?

appreciate any wisdom or insight.

 

[kapnd]

I’m not up on pertinent rules, but common sense says put the check valve as near to the transom as practical.

 

[High Wire]

Why not put it exactly like the original? Is there a problem that you are trying to solve?

 

[psneeld]

This I think is the first time I have heard of exhaust check valves in an Albin.. Most just have loops that prevent back flow.

Do you have a link to what check valve you are discussing so we could find out something to help?

 

[O C Diver]

Not sure I understand the purpose of a check valve in the exhast. If you're concerned about back flow, a lift muffler might be a better choice.

Ted

 

[kapnd]

Why not put it exactly like the original? Is there a problem that you are trying to solve?

Don’t believe for a minute that just because it came a certain way from the factory that that is the absolute best location.
Look at your system with an eye toward practicality, remembering how water is affected by gravity, and you may discover that many factory installations are marginal at best, and have room for major improvements.
Whenever possible, I’ll put at least a pipe diameter of fall in the last 18” of the exhaust run with the swing check valve in that.
Interesting reading re exhaust system geometry at sbmar.com, Tony’s Tips.

 

[albinalaska]

Why not put it exactly like the original? Is there a problem that you are trying to solve?

thanks for taking the time to reply-

there is a 70 gallon water tank that covers any practical way to inspect it.

 

[albinalaska]

This I think is the first time I have heard of exhaust check valves in an Albin.. Most just have loops that prevent back flow.

Do you have a link to what check valve you are discussing so we could find out something to help?

This I think is the first time I have heard of exhaust check valves in an Albin.. Most just have loops that prevent back flow.

Do you have a link to what check valve you are discussing so we could find out something to help?

appreciate the input- that’s interesting to hear and what i’ve been wondering too- if i even need it. there are lift mufflers as well but they’re not as low, relative to the engine, as i think ford lehman techs would recommend. (their at the back cabin level, not the engine room level)

the check valve i was looking into was a centek fiberglass style or anything else really that i could ideally put somewhere outside of the lazarette where even fit wouldn’t be a problem.

 

[albinalaska]

Don’t believe for a minute that just because it came a certain way from the factory that that is the absolute best location.
Look at your system with an eye toward practicality, remembering how water is affected by gravity, and you may discover that many factory installations are marginal at best, and have room for major improvements.
Whenever possible, I’ll put at least a pipe diameter of fall in the last 18” of the exhaust run with the swing check valve in that.
Interesting reading re exhaust system geometry at sbmar.com, Tony’s Tips.

thanks for the reply- can you clarify what you do again? what does “at least a pipe diameter of fall” mean? thank you!

 

[albinalaska]

also has anyone ever installed a lift riser to their lehman 120?

 

[Delta Riverat]

thanks for the reply- can you clarify what you do again? what does “at least a pipe diameter of fall” mean? thank you!

That means that the exhaust heading to the outlet should slope towards the water one pipe diameter in the final foot and a half.

 

[psneeld]

I didn't install it but relocated it so it had better angles to the inlet/outlet hoses in relation to the engine and exhaust port in the transom.