Merc 575 info / opinion

[Kelly O]

Originally Posted by JaayTeee

Mine had 388 hrs on them when 1 started
loosing a head gasket.

Everything else looked good inside,
I decided to freshen them up though,
and was able to go back with std.
rings and bearings.

We decided to upgrade them a bit
( heads, cam, ecm mods)
Courtesy of Mr. Horsepower1,
and should have them done in a couple of weeks.

They're a great engine, but like others have mentioned
head gaskets and blower problems are the most common
problem with them.

525's havent been trouble free either
( header leakage problems)

Please keep us updated on your results.
I am considering using Mr. Horsepower1 to upgrade my 575's, based on other's good experiences.

[Here's Johnny]

Originally Posted by Vinny P

We wanted to get new injectors, but found they are not available from Merc anymore. There are a few posts here about using replacement injectors. but since there seemed to be no issues with the original injectors, I just bolted them back on.

While we are on the topic......does anyone have a part number for replacement injectors.....

[Pesky Varmint]

My plan for replacement injectors if I ever need them:

Take a good injector into an injector shop. Purchase a new 60lb/hr
injector and compare the flow. If it isn't the same, buy a bigger/smaller
injector as necessary until I've matched them up.

If you surf the web on the subject, there is a range of injectors available for GM throttle bodies. Rumor says they are the 60lb/hr. Whatever, I would still try to match it.

Forget matching numbers on the injectors.

So far my 9 year old 450 hour injectors cleaned up just fine. For what it is worth they were 10% down on flow on average, and the clean up fixed a host of ills and they run like the scalded rabbits they were when new.

One other caveat regarding 575SCi relating to blower/throttle body:
I've resigned myself to the fact that some time in the future the day will come where you have to replace everything from the intake manifold up with a completely new set up. I've got a professional builder who will do that for me when the day comes.

Pesky Varmint

Originally Posted by Here's Johnny

While we are on the topic......does anyone have a part number for replacement injectors.....

[Quinlan]

I just took my Injectors to a diesel injector shop in town 2 weeks ago. They said the flow rate shoud be 115. Half of mine were under 100. They went thru all and installed new gaskets and all is good now.
By the way someone on here said that the kits for the 90 454ss chevy truck motor was the correct kit for gaskets and they were correct.
OF course when I said I needed 4, They said W T H and had to ship from Canada!! Got in 5 or 6 days.
Also said kit only came w one side of injector I said W T H now I need 8!!!! But truth b the kit is complete and now I have 4 kits for next time.

O and did I say it runs MUCH better now!!!

Quinlan

[JaayTeee]

[QUOTE=Vinny P;2890839] My biggest concern : I cant understand why did Mercury use flat tappet cam shafts? /QUOTE]


My thoughts are that the drives that were going to
be used ( XR's) determined the cam selection.

Use anything better, and it makes too much power,
and there goes the drive.

Mercury is know to build stuff conservative,
so the'll make it out of warranty.

[JaayTeee]

Originally Posted by Kelly O

Please keep us updated on your results.
I am considering using Mr. Horsepower1 to upgrade my 575's, based on other's good experiences.

Just waiting on the ECM's and cams to get here,
heads got here yesterday.

I've got to finish up a "frozen" small block project a guy
brought to me, and if nobody else breaks anything this
weekend, I can get back on working on my stuff

So far, they ( Gellners) have been a pleasure
to work with......I'll post results when they are done.

[Steve Zuckerman]

Originally Posted by Vinny P

I rebuilt Johns 575's this past winter. Along with what was said above I have a few issues I would like to bring out.
My biggest concern : I cant understand why did Mercury use flat tappet cam shafts? While rebuilding these engines, I was going to replace the cams with hydraulic rollers. The key was, we didnt want to re-map the ecu's. After several phone conversations with RMbuilder, it was determined that he could not exactly duplicate the flat tappet cam profile, to hydraulic roller. It would be real close, but not exact. Our concern was not having the correct vaccuum signal to the MAP sensor, possibly effecting the fuel curve. So, rather than take a chance, flat tappets were made and installed. One other issue is the throttle bodies. We wanted to get new injectors, but found they are not available from Merc anymore. There are a few posts here about using replacement injectors. but since there seemed to be no issues with the original injectors, I just bolted them back on.

Vinny,
You are correct that the map sensor and ECU won't be happy with the new cam/vacuum signals, nor will the existing fuel curve work with a better breathing, higher RPM cam. Remapping the ECUs for a different cam profile is no problem (I have a hydraulic roller in mine), as long as you have someone who has the software/knowledge/data base to do it. Speaking of remapping, raising the very conservative RPM limit on these motors from 5300 to what ever your cam profile needs are will help performance too. Horsepower comes with boost, and more boost comes with additional RPM. Unfortunately the stock cam is out of gas at 5600.
If anyone needs this service (ECU reprogramming) I recommend EB Marine here in Nashville (615-714-2944).
Regards,
Steve

[Vinny P]

[QUOTE=JaayTeee


My thoughts are that the drives that were going to
be used ( XR's) determined the cam selection.

Use anything better, and it makes too much power,
and there goes the drive.

Mercury is know to build stuff conservative,
so the'll make it out of warranty.[/QUOTE]

I agree with Merc building conservative, but they easily could have come up with a hydraulic roller cam that is real close to the flat tappet they used. If the profiles are very close, simply changing from a flat tappet to roller would not increase horsepower enough to even talk about.

[Vinny P]

Originally Posted by Steve Zuckerman

Vinny,
You are correct that the map sensor and ECU won't be happy with the new cam/vacuum signals, nor will the existing fuel curve work with a better breathing, higher RPM cam. Remapping the ECUs for a different cam profile is no problem (I have a hydraulic roller in mine), as long as you have someone who has the software/knowledge/data base to do it. Speaking of remapping, raising the very conservative RPM limit on these motors from 5300 to what ever your cam profile needs are will help performance too. Horsepower comes with boost, and more boost comes with additional RPM. Unfortunately the stock cam is out of gas at 5600.
If anyone needs this service (ECU reprogramming) I recommend EB Marine here in Nashville (615-714-2944).
Regards,
Steve

Steve,

I agree. Remapping is not a big deal IF the person doing it has the equipment and experience to do so. Personally, I would like to see it done on a dyno. That way, you know you are good.

[Bad Girl]

JT
Did Dean finish your motors? Would you share what he did and what results you haave with the new setup? thanks