Exhaust/Riser

[brendel]

What's inside the fiberglass exhaust

July 1st, 2020, 11:56 AM

inside the Fiberglass exhaust.

Does anyone know what's inside a fiberglass exhaust on an inboard ski boat? Baffles? Suppressors? . I own a '93 Ski Brendella, restored it, new engine, half cooling system, water pump etc. I just had both manifolds and risers changed, yet the starboard exhaust side is running hot 160 plus degrees after about 20mns, which is at least 30 degrees more than the port side. There are no obstructions/clogs that I can find in any of the hoses etc. Problem started with a blown exhaust hose (3.5"), which I replaced. I am hearing a small rattle in the starboard fiberglass exhaust portion of the system and wondered if something could be loose inside and creating some back pressure or trapping gases and water. Very puzzling... Thanks in advance for your comments.

 

Update

I pulled both risers for giggles and grins, my plan was to run water from a garden hose straight down the exhaust rubber hose and compare flow from the rear of the boat to see and there's any visible difference that would point towards restrictions on the starboard side. Interestingly enough I discovered that the gasket pattern is reversed from starboard to port side. I understood (maybe erroneously that the tab on the gasket is supposed to face forward of the boat and the closed cell on the back, which if that's the case the starboard side would be mounted correctly (incidentally that's the one getting hot), whereas the port side is facing the other way. Could it be that the port side is pulling all the water instead of "sharing" with the starboard side as a result of the gastkit being backwards? Either way something is not correct. Not to say that one of the baffles in the exhaust if there is one (it's a straight fiberglass piece) couldn't have come loose compounding the effect.

I appreciate your heads up.

[GSchmid]

I have a Ski Nautique, so it's got the single 2-inlet, 1-outlet muffler. Coincidentally, I just replaced my muffler because it was leaking water into the bilge. But I took a look inside before tossing it. It's a dual cavity resonator with 2 fiberglass baffles. I could see if your exhaust gets too hot (maybe blocked riser) the baffles could get hot and become unglassed, but more likely the rattling is contact with the floorboards..

 

Anyway, I shot some pix. One is a view through the inlet, one is through the outlet, the other is external.

 

 

[PatM]

Maybe a little off topic - but my buddy has a 98 Sport Nautique that I swear is getting louder. It use to be fairly quite, now it howls as if something may be wrong with the muffler. I can hear it from across the lake and without looking know he is out there. Unfortunately mostly pulling tubers.

[brendel]

Good info, thanks for the pics GSchmid, what year is your Nautique?

[ReallyGottaSki]

The riser gasket orientation mistake was a good find, the two water columns will be slightly different heights which could offset proper even flow.

 

Check the thermostat housing for old impellar bits too.

 

Typical dual mufflers have 2-3 baffles that cover about 1/2-2/3 the area, however they should be oriented at 12oclock. Maybe on a long prior service the muffler got oriented any old way