Lost 4 freakin MPH!

[GottaHaveIt]

Last week I sold my CMI headers :rolleyes and installed my original Mercruiser exhaust with silent choice. Took two attemps to install it since the first time I had several leaks but now it seems to be OK. I used teflon tape and RTV on the threaded plug seals and finally found some riser gaskets that weren't bent..they leak if they've been bent.

Anywho..I ran the boat yesterday with the GPS...best speed was 66 MPH...4,900 RPM. >: With the CMIs I was running 69 solid GPS MPH at 5,100/rev limiter.

I don't remember gaining that much when I installed the headers so I definitely did not expect to lose that much!

Gonna have a compression check done soon..hopefully I did not damage the valve seats or valves by running it so lean when I had the headers on. My initial plan was to buy a recal ECU and fuel pressure regulator to get the air/fuel ratio back on line but I'm too cheap...:rolleyes

Now I have a lowly neutered 25 Outlaw and it sux being so slow..gotta get that 29 Outlaw with twin 500s now huh...

[TeamBajaMarine]

Chris,
remind us, why did you dump the headers in thefirst place and then go back to a restrictive Merc manifold?

[GottaHaveIt]

Money..I'm too cheap to spend $1,000 for silent choice tailpipes from CMI. And I needed to richen the mixture with a fuel pressure regulator and reprogam the ECU which was another $500 or so.

I figured that at the most I'd only lose 2 MPH but not 4!!
Hope I don't have any valve sealing problems from running lean so long.

[Baja Daze]

Ouch. :(
I didn't realize the stock exhaust is that restrictive. 4mph is pretty significant. You may be correct with the lean condition though. I've heard the 496's are very tempermental to any modifications, even something as simple as exhaust. The ECM need to be modified with any changes.

[davesoutlaw]

Any motor is tempermental to changes With computer controlled engines it is harder to modify just the engine and not the computer since it controls the air fuel ratio. As far as the 496's are concerned headers wont do any bit of improvements except looks the exhaust manifolds on them are high flowing almost equivant to a set of headers (so ive been told)

[GottaHaveIt]

Ran the 25 again tonight alone with 1/4 tank of fuel. Managed to get 69 on the speedo and 68.2 on GPS, and 5,100 RPM with the trim way out for speed.

Next time I fill it up will be the real test. With the headers it would run a solid 69 even with nearly a full tank.

I do like having the silent choice back though! ;)

[davesoutlaw]

Chris
Might be time for a PROCHARGER.