Exhaust Angle

[dlp_90731]

Hi everybody! Had a question about the degrees of drop the exhaust should be from the manifolds to the transom? I attached a couple of pics. Thanks in advance.

 

[Bondo]

Re: Exhaust Angle

Ayuh,.... Looks like it's fallin' away alright,...

I'd still put shutters in it...

 

[Tahorover]

Re: Exhaust Angle

Use flappers on your tips.

 

[dlp_90731]

Re: Exhaust Angle

Thanks Bond-O and Tahorover. Basically I want to lower the deck and need to change the risers to a lower profile. I wanted to make sure that I would have the correct angle to prevent back flow of water. I do have flappers at the moment. You can see the height of the old deck in the second picture right above where the exhaust goes through the transom. That's where I will be bringing it down to.

 

[Lyle29464]

Re: Exhaust Angle

If your total drop is less than 13 inches you will need to get creative.

 

[dlp_90731]

Re: Exhaust Angle

Lyle the required drop is 13" from manifolds through to the transom? I will measure this weekend and see what it's at presently. Thanks for the response.

 

[Bondo]

Re: Exhaust Angle

Lyle the required drop is 13" from manifolds through to the transom? I will measure this weekend and see what it's at presently. Thanks for the response.

Ayuh,.... It's 13" from the tipping point of the risers, to the water level, Outside the hull....

 

[dlp_90731]

Re: Exhaust Angle

Well looks like I will need to fix it. I'm pretty sure it's a few inches less than 13". Maybe they raised the deck and risers trying to get close to that drop? The flappers are at the water line at the transom.

 

[Tahorover]

Re: Exhaust Angle

Were did this 13" spec come from?

 

[dlp_90731]

Re: Exhaust Angle

It was suggested farther up in the post. Is this correct? I am game for all information and options just want it done right. Thanks

 

[Ned L]

Re: Exhaust Angle

Tahorover, ... I was wondering the same thing. That sounds like a nice number, but there are also lots of boats out there that can't accomplish it.

........ I know, there are also lots of boats out there that have lost engines from water sloshing back up the exhaust & through open exhaust valves.

 

[Bondo]

Re: Exhaust Angle

Were did this 13" spec come from?

Ayuh,.... I know it can be found in Mercruiser installation manuals, 'n I pretty sure it's also listed in the Volvo installation manuals....

That's why some motors need riser blocks under the risers, 'n some don't.....

 

[Ned L]

Re: Exhaust Angle

Thank you Bondo. I hadn't heard of a published dimension before. 13" is a pretty 'gut instinct' logical dimension. - That's got me thinking, I'll take a look in Some Chris Craft ML & KBL manuals I have.
also, for the O.P. The angle of the exhaust is really not that important, as has been said, it is the dimension between the bottom of the exhaust path inside the riser and the true waterline (loaded) that would be important.

 

[Tahorover]

Re: Exhaust Angle

Ayuh,.... I know it can be found in Mercruiser installation manuals, 'n I pretty sure it's also listed in the Volvo installation manuals....

That's why some motors need riser blocks under the risers, 'n some don't.....

OK now were does one find the inboard shutters? I can only find I/O shutters?

 

[Bondo]

Re: Exhaust Angle

OK now were does one find the inboard shutters? I can only find I/O shutters?

Ayuh,... That's a different question, but usually, at the end of the thru-hulls, outside the boat....

 

[dlp_90731]

Re: Exhaust Angle

I do have blocks in between the manifolds and risers. So is it safe to say this exhaust system is set up correct? It has no known issues I'm just making sure that it is correct when I go forward with restoring everything. Thanks guys you have been a great help.

 

[Bondo]

Re: Exhaust Angle

So is it safe to say this exhaust system is set up correct?

Ayuh,... The Safe way to know is to Measure, 'n See.....

Who knows if the last guy got it Right, or Wrong,..??

By the looks of yer picture, you've got clearance for 6" blocks,... those look to be 3"...

 

[dlp_90731]

Re: Exhaust Angle

10-4 Bond-o! My boat just back from a film shoot of the Mentalist. Somehow got picked to be an extra. I'll have a chance to measure it. Will get the figures to you guys.

 

[Luhrs28]

Re: Exhaust Angle

I read recently that the exhaust down-pitch should be at least 1/2" per foot of tubing. I can't remember where I saw that though.

 

[Tahorover]

Re: Exhaust Angle

I read recently that the exhaust down-pitch should be at least 1/2" per foot of tubing. I can't remember where I saw that though.

That makes more sense than 13".