Life Expectancy Of Merc 575 Sci

[thunderdan]

i AM WONDERING WHAT TYPE OF LIFE EXPECTANCY OF THIS MOTOR BEFORE REBUILD? HOW MANY HOURS HAVE YOU SEEN ON THESE?

[mcollinstn]

It's a solid motor on a good platform.
Relatively low boost. Low compression blower pistons.
Pretty mild cam and mild springs.

Keep the boost stock, prop for 5000-5100, do not overheat it, warm up the oil before hammering it, keep WOT operation down under 5% of the time, run good quality gas, and stay on top of your fluid changes and you should expect normal (400 hour) service intervals.

Up the boost, run questionable fuel, let it overheat into the alarm buzzer, and do other things to tempt detonation, and you are making your own luck.

Keep in mind that with all BBC's, valvetrain aggressiveness is the determining factor on service intervals. The wilder the cam and stiffer the springs, the sooner you gotta service it. Bottom end parts are usually no worries.

[Canada Jeff]

Is it fair to say the cam is less agresive than a hp500efi??

[zahndok]

It's my understanding that it is less aggressive than the 500efi but I'm not sure you can compare NA to blower as far as what's needed in a cam.

Anybody know what Merc uses for the major internals such as crank, pistons, valve train. Basic GM parts? or other Brands?

[Canada Jeff]

I am just trying to gage the valve spring stress compared to my hp500efi. If the cam is not as agressive, one would have to believe the springs are not under as much stress.

I do agree with keeping WOT to a minimum! To bad. They sound great!

[Biggus]

Originally Posted by Canada Jeff

I am just trying to gage the valve spring stress compared to my hp500efi. If the cam is not as agressive, one would have to believe the springs are not under as much stress.

I do agree with keeping WOT to a minimum! To bad. They sound great!

The cam on the 575SCI is just a mild hyd flat tappet cam. Lift is very conservative (.559 I believe) and mild spring pressures.

I agree with mcollinstn, treated right they will give you good service.

[tj309]

I have an Active Thunder Cat 24' with twin ProMax 300's. What type of boat do you have?

[mcollinstn]

Originally Posted by zahndok

It's my understanding that it is less aggressive than the 500efi but I'm not sure you can compare NA to blower as far as what's needed in a cam.

Anybody know what Merc uses for the major internals such as crank, pistons, valve train. Basic GM parts? or other Brands?

500efi is a more aggressive cam. Faster ramps. More lift and duration.

A 500efi and a 575SCi share the following components:
Gen 6 siamese 4.470" GM 4 bolt block.
Forged steel GM crank.
"Merc Racing" forged rods.
GM rectangular port iron heads.
Crane gold roller rockers.

A 575SCi uses:
Inconel exhaust valves (500 efi "may" have those, but I don't think so)
Flat tappet hydraulic cam
Mild springs
Dished Blower pistons

500efi uses:
A more aggressive hydraulic roller cam
Springs matched to the cam
JE flat top pistons

[thunderusone]

Originally Posted by mcollinstn

500efi is a more aggressive cam. Faster ramps. More lift and duration.

A 500efi and a 575SCi share the following components:
Gen 6 siamese 4.470" GM 4 bolt block.
Forged steel GM crank.
"Merc Racing" forged rods.
GM rectangular port iron heads.
Crane gold roller rockers.

A 575SCi uses:
Inconel exhaust valves (500 efi "may" have those, but I don't think so)
Flat tappet hydraulic cam
Mild springs
Dished Blower pistons

500efi uses:
A more aggressive hydraulic roller cam
Springs matched to the cam
JE flat top pistons

mcollinstn...You've got mail!

[Canada Jeff]

Thanx for the info! Are the Flat tappets not as good as the rollers?