Question about 575 SC blowers?
03-14-2012, 07:02 PM
#1
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Question about 575 SC blowers?
This winter, it was time for a freshen up on a friends set of 575 SC blowers. I rebuilt these engines a few years back to stock specs. Other than going .030 over on the bore, no modifications of any kind were done. The engines have run flawlessly since then. Come to think of it, they ran great before I tore them down. Getting back on point... I just got the blowers back from a reputable rebuilder. The rebuilder choose to add teflon wipes to the rotors. I must say, they did a great job. However, my concern was... will the addition of teflon wipes increase boost? A call to the rebuilder comfirmed my thoughts. He claims the wipes will increase boost by 1-2 psi. He claims no big deal, no worries. I tend to think differently. Although I doubt it would get to the extreme, I dont want to see 2 engines melt themselves down. I will keep an eye on the plugs for sure.
I have been on the boat many times running hard. I have never seen the boost gauge go above 3 psi. Now he is telling me the wipes will add 1-2 psi. With that in mind, we are talking about the possibility of increasing boost by 66%. In my book, boost = horsepower = heat. Heat needs fuel or an intercooler to cool down cylinder temps. I know Merc sets up their fuel curves safely on the rich side. But is the curve rich enough to handle potentially 66% more boost?
Has anyone done this before?
I have been on the boat many times running hard. I have never seen the boost gauge go above 3 psi. Now he is telling me the wipes will add 1-2 psi. With that in mind, we are talking about the possibility of increasing boost by 66%. In my book, boost = horsepower = heat. Heat needs fuel or an intercooler to cool down cylinder temps. I know Merc sets up their fuel curves safely on the rich side. But is the curve rich enough to handle potentially 66% more boost?
Has anyone done this before?
03-14-2012, 07:40 PM
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This winter, it was time for a freshen up on a friends set of 575 SC blowers. I rebuilt these engines a few years back to stock specs. Other than going .030 over on the bore, no modifications of any kind were done. The engines have run flawlessly since then. Come to think of it, they ran great before I tore them down. Getting back on point... I just got the blowers back from a reputable rebuilder. The rebuilder choose to add teflon wipes to the rotors. I must say, they did a great job. However, my concern was... will the addition of teflon wipes increase boost? A call to the rebuilder comfirmed my thoughts. He claims the wipes will increase boost by 1-2 psi. He claims no big deal, no worries. I tend to think differently. Although I doubt it would get to the extreme, I dont want to see 2 engines melt themselves down. I will keep an eye on the plugs for sure.
I have been on the boat many times running hard. I have never seen the boost gauge go above 3 psi. Now he is telling me the wipes will add 1-2 psi. With that in mind, we are talking about the possibility of increasing boost by 66%. In my book, boost = horsepower = heat. Heat needs fuel or an intercooler to cool down cylinder temps. I know Merc sets up their fuel curves safely on the rich side. But is the curve rich enough to handle potentially 66% more boost?
Has anyone done this before?
I have been on the boat many times running hard. I have never seen the boost gauge go above 3 psi. Now he is telling me the wipes will add 1-2 psi. With that in mind, we are talking about the possibility of increasing boost by 66%. In my book, boost = horsepower = heat. Heat needs fuel or an intercooler to cool down cylinder temps. I know Merc sets up their fuel curves safely on the rich side. But is the curve rich enough to handle potentially 66% more boost?
Has anyone done this before?
03-15-2012, 04:45 PM
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Dont worry, enjoy the added boost. Been running teflon tipped rotors with no issues. If the blowers were worn, and not operating efficiently, that can make some heat.
4-5psi on a stock 7.5 or 7.7:1 merc engine is not a problem. I wouldnt worry about adding a chiller until you exceed about 7psi. come to think of it, I am pretty sure all the merc factory blower setups, ran about 4-5psi. (525sc, 575, 600sc) Theres probably plenty of fuel in the stock mapping, although im not too familiar with the 575 setups.
4-5psi on a stock 7.5 or 7.7:1 merc engine is not a problem. I wouldnt worry about adding a chiller until you exceed about 7psi. come to think of it, I am pretty sure all the merc factory blower setups, ran about 4-5psi. (525sc, 575, 600sc) Theres probably plenty of fuel in the stock mapping, although im not too familiar with the 575 setups.
03-16-2012, 01:33 AM
#8
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The 575SCI's should have about 4.5#'s boost stock. I highly doubt there will be any issues with even up to 6#'s.
The 525SC is 5.5#'s stock and I was running almost 8#'s with stock carb jetting. I only bumped my jetting a few sizes when went to a bigger roller cam.
The 525SC is 5.5#'s stock and I was running almost 8#'s with stock carb jetting. I only bumped my jetting a few sizes when went to a bigger roller cam.
