Any time you truthfully reveal what you have done...there are always critics. Bottom line...all things considered I'm happy with what I have and it performs very well.

Sure. I'll take a stab it.

It will be much faster if you're wife is driving it.

Loud is a relative term. Several factors come into play with 'loudness' in my boat. If the bimini top is up the boat is perceived to be louder inside the boat since the sound waves are bouncing off the water, up and into the bimini top reflected inside. Obviously the true dB reading aft of the boat remains virtually unchanged. I don't have readings for the current motor, but stock Merc 350 Mag with Rex Marine Sound Selector system was about 82 dB at idle, cutouts closed and if I remember about 86 dB with the cutouts open. New motor has more bark, but I haven't pulled the meter out to measure it and I only have straight through hull.

I can, and have run inline silencers and they do cut the dB by about 6-8 but also choke down the top end rpm by 300-500 so I almost always leave them out. With a milder cam you may not have that problem. There are several exhaust cut-out systems available which can also give you some sound options, but they should be avoided when cams get more aggressive since the butterfly valves diverting the exhaust down the Y-pipe when running closed can exacerbate potential reversion issues with performance cams. They also add expense. $600-800 just for the system, not including additional exhaust hose, thru hull tips, and the labor required to cut the holes.

To answer your question, I would be hesitant to run the Comp 276 with a diverter type exhaust system.

Definitely faster when the wife drives it. After all, this one is hers.

That does sound like my boat. The 305 was missing when I bought the boat but most everything was still in it. I guess for the time being i'll look for a cam that is a step above what would have been in a 5.7 I can swap later if I still want. What kind of HP is a sx cobra duo prop good for? Am I going the wrong direction again thinking about comps XM270 ? Advertised at 5200rpm or is it doable through the stock leg?

Exactly. As long as your happy that's all that counts.

Is this cam doable in my 383 exhausting through the stock leg and would it actually reach the advertised rpm? What kind of hp and tq numbers could I expect from it?

Lunati 20080720 (Formerly Part Number 60120) Chevrolet Small Block LT1, LT4, & 1987-Present Hydraulic Roller Voodoo Camshaft RPM Range 1600 - 5600 Lift .507"/.515" [email protected] 211/219 LSA/IAC 112/106
Excellent choice for stock to mildly modified engines, works well with OEM style injection, great inboard/outboard marine cam for economy and sking. Good mileage and torque increase.



RPM Range: 1600 - 5600
Lift with 1.6 Rocker: .507"/.515"
Duration @ .050": 211/219
Advertised Duration: 262/270
LSA/IAC: 112/106
Valve Lash: Hyd/Hyd
Cam & Lifter Kit: 20080720LK
Complete Kit: 20080720K
Lifters: 72910-16
Springs: 73943-16
Retainers: 75742-16
Locks: 77003-16
Valve Spring Kit: 73943K1
Valve Seals: 78501-16
Timing Set: 93026
Pushrods: 5040-16
Rocker Arms: 85340-16

38
You will likely incur pumping losses (both intake and exhaust) that will inhibit you from reaching 5600 RPM. It will be beneficial to address your exhaust lobe due to the downstream restriction the log manifolds present. The displacement has increased ~9% from the original spec, increasing the spent charge proportionally. I would suggest increasing intake duration, reducing your exhaust bias (from the new intake lobe) to: (1º-4º) It will also benefit you to pay close attention to your ECL.

Bob

If I give ya a hundred down would you help make this problem go away rmbuilder?:D

Or suggest an off the shelf cam that will let me get the most from this 383 that I can exhausting through the stock leg?

I have been offered a brand new hyd roller cam and roller lifters a long with new roller rocker arms, chain and gears. valve springs push rods from a 325 HP 5.7 mercruiser that is being reworked for opposite rotation. He is asking $375 for everything. I can't hardly turn that down. Will my 383 gain or lose running that hyd roller cam? Pretty sure he said it was a duel pattern cam. He also said the cam is a 5,000rpm cam. Everything is for my same year engine, a 98.