Exhaust replacement

[rveldman1]

I obviously need to re-do the exhaust on my 1974 Grampian. Question is: should I duplicate the riser (I can add 3 inches to height) and eliminate water muffler or use the brown thing?

[Al Schober]

OK, I'll jump in here.
First, I've never used a mixing elbow like the brown thing. There's a history of them here on the forum getting clogged. Is yours new or is it a used (questionable) unit from eBay?
I have used a riser, and they are fine. Taller is better. The only down side to them is they take a lot of space and require a lot of insulation to protect your boat.
I'd be tempted to try the mixing elbow if it's a new unit. Otherwise I'd build a riser of known performance. Might even think about stainless..

[joe_db]

I wouldn't leave the water lift out of the system.

[edwardc]

+1 on leaving out the brown mixing elbow and building a stainless riser.

+1 on NOT leaving out the waterlift muffler!

[rveldman1]

The brown thing is from a used engine I aquired that would not run for longer than 30 min. Perhaps the brown thing was it's problem.
I am trying to reduce back pressure in the exhaust system. Moyer has exhaust setup from catalina diagram that they suggest could be used without a water lift muffler?

[rveldman1]

I am trying to find out why my plugs foul in less than 8 hrs of running. Identical Black sooty fouling on all 4 cyl .
Vacuum at idle is 18-20, and goes to zero at 3/4 throttle. Cyl compression is 90, 95 , 95, 90. Exhaust is blue-gray on start, clean at 165 degrees, timing is at tdoc. I run the slightly hotter plugs and engine starts incredibly well.