Need muffler/ fumes advices

[Cooler]

Another possibility is the fuel in that tank may have some additive or treatment in it that creates a stronger odor. I have seen where people put too much Seafoam or Stabil in one tank and that makes one side exhaust smell stronger. Are you able to get non-ethanol gas in the tanks? The 454's have 142 degree t-stats in them. You may consider going to 160. er

[chpsk8]

Good idea Cooler - warmer stats along with a general tune up would be a pretty cheap and easy place to start. If the carb has been rebuilt one would think it would be ok, but having had rochesters on previous boats I know they can use a tweak sometimes. saying that...the last one I had rebuilt was plug and play.

Have you cleaned the flame arrestor? Keeping that clean will allow more airflow into the motor. Take some carb cleaner and just blast it until it's clean. Let it dry before starting.

Cap and rotor cleaning at the least, and replacement would be better. Sometimes we think things sound great until you go through the basic tuneup steps and then it's even more amazing how smooth your motors can get.

Keep playing with it, sounds like there's room for improvement.

[Dustin07]

we recently did new caps, and actually new carbs by previous owner. I don't think they were tuned well because my port motor runs too rich, but I'm working on that with my mechanic.

I bring that up because despite knowing it's running a little rich, my fumes were exactly like you described. definitely too noxious for my wife who is quite sensitive to the smell of exhaust fumes on a hot day, it will make her want to vomit.

We redid the risers, elbows and manifolds because they were due, but also discovered a small leak in the port side manifold. after doing this job, the fumes are incredibly minimal now. now the boat just smells like a carbureted SBC.

any chance of a manifold leak? sometimes you can hear it if you know what you are listening for.

[Hudsteve]

Dustin

How would I go about checking the mainfold for a leak?
I had the carb tuned up and the fumes are better but still enough that sensitive people can easily tell they are there

Also this engine (port) is very loud, sounds like riding on the back of a Harley and no one can even think about talking while underway.

Easy way to minimalize the noise?

Thanks

[Dustin07]

hmm, 454's are big blocks and in my opinion already have a cooler sound than my SBC's but with the hatch closed you can barely hear our motors from the bridge. At least, the sound is faint enough that when one is running I really have to strain my ear to hear the second one start up. our manifold leak you could hear, but only barely. My mechanic pointed it out to me. and I can tell he was 100% right because I have now redone the manifold and risers/elbows full exhaust on both of my motors and we have basically zero fumes now. it's much better. you can try this approach, although my leak was on the lower side of the manifold so it would have been harder to see:

https://www.google.com/search?q=how+to+ ... PhfSNmA479

[bud37]

Source of the post At least, the sound is faint enough that when one is running I really have to strain my ear to hear the second one start up. our manifold leak you could hear

Do you have the Davis underwater exhaust/muffler out the center stern in your model ?