NEED TO CHANGE EXHAUST MANIFOLDS ON 502MPI'S LEAKING AT RISERS BADLY EVEN AFTER RPLACING GASKETS.WHAT ARE THOUGHTS ON BEST SYSTEM FOR SALT WATER USE. NOT PLANNING TO MAKE ANY MODS TO ENGINES AT THIS TIME.

I just added a set of Gils Wet Offshore manifolds. I can't tell you anything about any power increase. I am not expecting to see any big changes with it.

Go stock if you are not going to modify. They last a while as long as you flush them out. You from what I have been told by many will not gain any hp with aftermarket.

Jon

On my old boat ('00 PQ 280 w/ 502) I put on Stainless Marine exhuast.

Aluminium manifolds / stainless steel risers. NO corrosion!

Got about 100 more RPM too.

Go with the best! CMI Elbow Tops 317L stainless steel construction 2 year warranty.

Go with the stainless marine system. you get a 50 month warranty. i used to have a 222 chris craft stinger w/ 454. it ran 62 when i got it. changed to a 454 mag and ran 62. changed carb and camshaft and ran 62. put on a set of their manifolds and ran 70. that sold me. now i have a 31 cig and run them w/ dry exhaust to tips and have had no problems and they sound great!!!

I prefer the Stainless Marine Or the more expensive CMI to the rest. I can tell you I have seen improvement over stock on every application. The trick is use a GPS not a Speedo. The stock big block exhaust is very restrictive even for a stock engine. Remember there is no monumental gains just baby steps.

Randy

Since there seems to be very little gains in top end HP/speed... do these exhausts ie. CMI's provide more low/mid range torque than stock manifolds? How much less do they weigh?

I recall reading an advertisment for the CMI platinum series for a 454MAG with a dyno chart showing a gain of +/- 50HPs. What's up with that?

I can tell you from experience the weight savings are incredible. Just replaced both sets on my Formula in the past 12 months and they are a mutha. 80lbs is what the UPS packing slip said and I won't argue a bit with them. Add on cast risers and 3" spacers and that makes for one obese package (4x85/90=340/360lbs?). Imagine being bent over like some sort of contortionist and attempting to lower an 80+lb manifold down, GENTLY, into your bilge, stabbing it into your 4" exhaust hose (since the cast risers can't be installed separately) and then holding it in place with one hand while you start a bolt with the other. BTW, you can't see the bolt holes you are trying to stab! Sounds like fun, doesn't it? Actually, after fighting the first set I used some short 3/8 studs at each end and hung the manifold on these studs until I could get some other bolts started. I went the stock manifold route simply because I won't be searching for any more speed from this boat (Formula 311 454 mags) and the performance manifolds weren't worth the extra $$$ to me. It runs 65-67 GPS and will do it all day for weeks on end. If you aren't worried about any gains in HP or speed, you can save a bunch of money by finding a good used set of stock manifolds. If you want the weight savings, possible HP increase etc., go with the aftermarket stuff. Stainless does have some nice equipment.

Had 502 efi's and went with stainless marine. You will see a tremendous amount of improvement in low and mid range torque. Some improvement on top end, Definitely worth the investment.