Life Expectancy Of Merc 575 Sci
 

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

Re: Life Expectancy Of Merc 575 Sci
 

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.

Re: Life Expectancy Of Merc 575 Sci
 

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

Re: Life Expectancy Of Merc 575 Sci
 

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?

Re: Life Expectancy Of Merc 575 Sci
 

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!

Re: Life Expectancy Of Merc 575 Sci
 

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.

Re: Life Expectancy Of Merc 575 Sci
 

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

Re: Life Expectancy Of Merc 575 Sci
 

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

Re: Life Expectancy Of Merc 575 Sci
 

mcollinstn...You've got mail!

Re: Life Expectancy Of Merc 575 Sci
 

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

Re: Life Expectancy Of Merc 575 Sci
 

So if ran hard, like in a race boat, you could expect about 30 hours of service?

Would the 525 last longer?

Re: Life Expectancy Of Merc 575 Sci
 

Guys:
I have a 575SCi in a 28' Nordic. I bought the boat because my best friend had run a 575SCi in a 29' Fountain for 3 years with no issues at all except routine maintenance. It is reliable and fast (87/88GPS). Only mod is the AZ Speed and Marine boost kit, which works very well, and has had no adverse effect on reliability whatsoever. The boat now has 250 HRs, and ran as well as ever last weekend.
My luck, unfortunately wasn't quite as good. I bought the boat with 102 HRs. Since it was used and out of warranty, I immediately installed the updated AZ Speed and Marine boost kit with similar good results. However, a screw backed it's way out of the rear throttle body, went through blower which cut it in two, half going into #5, and half into #8 :mad: ............
After pulling it down, it required 2 new pistons, and I had the heads and valves cleaned up. We put all new FelPros, bearing and rings in the motor since it was out. OH YEAH, LOCKTITE ALL the fasteners on the throttle bodies too :rolleyes: !
We reinstalled the motor @ 9:00 the night before our local Poker Run, and I was the 1st single engine/1st vee to the 1st stop the following morning :D . So I guess you could say it was broken in rather aggressively.
Since then I had the Blower Shop freshen up the Weiand 256 and repair my rotors, which were dinged up, and installed a Whipple intercooler which has really woken the motor up. Even though I had some bad luck with mine, I'm still sold on the motor. It's in a very conservative state of tune from the factory, and should last 500 hrs. easily in stock form (depending on how you drive it of course). Even modified like mine, it cold starts right up, idles like a (noisy) kitten, and rips when called upon.
Regards,
Steve

Re: Life Expectancy Of Merc 575 Sci
 

If you would have put the intercooler on sooner as a screw catcher you probably would have only rebuilt the blower. :D :evilb:

Re: Life Expectancy Of Merc 575 Sci
 

350 hours on two 575SCi's in 35 Nordic.

One blower overhauled last summer.

Zero oil consumption.

I asked Larry Peto of Larry's Engine and Marine about
when I should overhaul them. He agreed that they are
actually pretty mild motors and don't touch them until
they need something (consume oil, low compression, etc).

I would say just check your compression annually, do regular
oil testing (Larry does this, I don't do it only because I'm too
lazy), and watch oil consumption. I'd put money on them being able to go over a 1000 hours without really needing anything. I'll find out for you.

By the way I'm an old man so I don't spend 100% of time
at full throttle. I'd say over 70% of the engines running hours
have been between 3500-4000 rpm, and never over 5200.

Wish the XR drives were half as reliable (never had them grenade but need complete overhauls about every 200 hours because they wear out gears). I consider an 8000 lb 35 ft
boat with 575's the limit for XR drives.

Pesky Varmint

Re: Life Expectancy Of Merc 575 Sci
 

What is the speed on the 35 575sci nordic?

Re: Life Expectancy Of Merc 575 Sci
 

We have XR's on our 36 Apache, and I'm sure she weighs around 10 000lbs. I agree if we see 200 hours out of out drives I'd be happy!

Re: Life Expectancy Of Merc 575 Sci
 

Mid 90's GPS, Havasu, cool weather, 1/2 fuel, two people.
Never dialed the boat in, 32 pitch props.

Pesky Varmint