Re: What exhaust for 311?
 

Haven't done yet but am becoming all too aware of what could happen. like a lot of us, my business partner (the Mrs) isn't so excited about spending $4k. I'm working on her.

Re: What exhaust for 311?
 

I had a '92 boat I bought off Lake Winnipoopie with a single 454 mag 365 hp, everything stock. Ran in Newburyport for 3 seasons. Exhaust looked ok on the outside, but I had the motor out to work on the hull, and decided 10 years was enough. Once the exhaust was off, you could see that it was leaking on the inside right into heads! If I had went one more season, BANG! Glad I caught it when I did.

Food for thought, and nightmares (sorry!)

Re: What exhaust for 311?
 

Same thing happened to me on my 242. Took it out once too often and that was that. Rule of thumb: if you can see ANY water leakage on the outside, you can bet it's leaking on the inside. That's why I changed the exhaust on Outlaw when I did. It had just started showing a leak on the outside where the risers bolted to the manifolds. Never even started it once I noticed that. Motors had run find last time I shut'em off and wasnt' about to take the chance.

Re: What exhaust for 311?
 

Same story here, guys. Actually had those NICE plastic water inlet fittings/drains on my Merc manifolds and they were leaking and allowing water to run down on top of the manifold bolts. Bolt heads literally crumbled when I put a socket on them. Decided if I was going to pull the motors to get manifolds off I would go ahead and freshen ( :rolleyes: ) them up at the same time. Upon teardown, one set of heads completely ruined and the others already had the beginnings of water damage. Needless to say the merc anchors went overboard (along with 300+ lbs) and in came the EMI's. Of course, with new EMI's I couldn't just "freshen" the motors. :D :D :D

Re: What exhaust for 311?
 

I am going with the EMI Thunders. CMI wants almost 4000$ per motor to make them fit right. Not worth it to me. I'm will need that money for drives if they dont hold up. Bolt up and forget about 'em factor is huge in my book too. Thanks for all the info.

Re: What exhaust for 311?
 

Croozin2, what exactly do you have under the hatch? What speed are you getting?

Re: What exhaust for 311?
 

Croozin, nice lookin motors - 1st time I have seen the 454mag flat hat filters actually look good.

Looks like you had the same issue with the oil drain lines that are supposed to be able to be pulled out the bilge drain but ends too big to fit. I put mine in just about the same place. Are those quick connects on the end??

Re: What exhaust for 311?
 

Oops. Above I posted that I have the risers welded shut. That's not the case, it was the manifolds, but you probably knew what I meant. The EMI stainless risers just have a solid flange on the bottom, water gets in via a hose.

Re: What exhaust for 311?
 

Sorry so late getting back - been at the river all weekend! I was looking for a previous post I made so I could just copy and paste but here goes,

.030 over, 9.5:1cr, 461ci, stock crank & rods
990 GM heads lightly massaged, Ferrea Valves, 2.30 - 1.88, Crane Gold Rockers
Cam by Cam Motion, Single Pattern Hyd, 236 @ .050, .561 lift
EMI Thunder Exhaust w/stainless 3" extended risers
Crane Hi-6 Marine Ignition w/stock TB-IV dist
Stainless x-overs and t-stat housings
Merc/GM Dual Plane Aluminum Intake
modified Q-Jets (Yeah, I know) w/1" open spacer

Didn't dyno my particular motors but this package has netted anywhere from 498 to 512hp on previous builds. Diamond Engines in Hammond Louisiana did all of the bottom end work. I used to drag race in super stock with the guy 15-20 years ago and he builds some strong motors. After much work with the carbs (Q-jets are really finicky w/ low vacuum signal) the boat increased from 63mph with the stock 454 mags to 72mph and blowing right through these 23" mirages (5500+ rpm). It really accelerates, though. I'm figuring with some 25" Mirages or 24 Bravos or Q-IVs I should see ~75.

Re: What exhaust for 311?
 

Good eye on the quick connects, CMG! I had been using the old method of vacuuming out through the dipstick tube and you never quite get everything out. I had the hoses made up at a local hydraulic hose shop and added the quick connects on the end. Took a 5 gallon plastic bucket and mounted a Teel 12v impeller pump to the top of it. Put the male quick connect on the inlet hose and drilled the top of the bucket and routed the outlet line straight into the bucket. Makes for a sanitary little package.

Thanks for the compliment on the motors. I always like to be a little different so I thought the silver powder coated manifolds topped off with the original flame arresters and covers looked nice (makes people wonder just how stock/modified it really is, too!). :D