Turbocharging a Mercruiser 502, guidance required.
10-31-2014, 09:51 PM
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Turbocharging a Mercruiser 502, guidance required.
Hi Guys,
I've been a member of this forum for a few years now but more a reader than contributor and I think the time has finally come to reach out :-)
I currently have a 2000 29 Scarab which I love but its time to upgrade things a bit and rather than learn from my own money eating mistakes I thought
It best to seek some advice from the knowledge full.
I am based in Ireland and familiar with european cars but American Marine stuff is completely forgien to me.
My Scarab was running a single 7.4 MPI 310hp which pained me as my previous boat had two 5.7 twin turbo motors and wanted to go down a similar
route so when I saw some value in the form of a low hour Mercruiser (Forged pistons, steel crank and low compression)502 Carb engine 415hp
which had been fitted with a Cutler EFI system 1000CFM (similar to Holley), MSD 6M-2, Mercruiser Thunderbolt IV Distributor and a set of exhaust headers I took a punt.
I then acquired an old school Gale Banks Stage Three Twin Turbo Setup. which consisted of 2 Gale Banks Exhaust Manifolds,2 Water Cooled Turbos and 2 Intercoolers.
There currently isn't the ability to control boost as it simply is preset via a hole in the exhaust side that allows gasses to bypass the turbo. From what I can find
out the system runs about 8psi stock and some people have restricted the bypass to increase up to 12psi. I can block these off and weld in some external wastegates if need be.
Here are two links to similar set ups:
http://www.performanceboats.com/part...turbo-kit.html
https://www.flickr.com/photos/menard...7616396786774/
https://www.flickr.com/photos/menard...7619340912710/
My current thoughts are to ditch the outdated Cutler EFI ECU and replace it with Holleys HP EFI (550-604) and run some bigger injectors and to remove the throttle
body and mount the intercooler on top of the inlet manifold and fit the throttle body where the carb would sit?
Is this a set up that would work anyway well? I really need to know what approximate power level these engines can run safely in stock form so that I can match the correct
injectors and to get the correct GPH fuel pump etc. I estimate a figure of about 700hp would that be a fair assumption?
Again I have no idea about American products and don't know if my existing Distributor and MSD ignition box me up to the job? are they standard
block connections that are plug and play with the Holley 550-604 kit?
Would I have a worthwhile benefit from sticking in a set of cams and rockers while the engine is out of the boat?
I know I'm probably going to be told to ditch the old kit and get a procharger but I just like the turbo idea.
Any advice or guidance as to how I would best set this up to maximize its potential on a reasonable budget would be greatly appreciated.
Many thanks from the Land of Eire!
Jay
I've been a member of this forum for a few years now but more a reader than contributor and I think the time has finally come to reach out :-)
I currently have a 2000 29 Scarab which I love but its time to upgrade things a bit and rather than learn from my own money eating mistakes I thought
It best to seek some advice from the knowledge full.
I am based in Ireland and familiar with european cars but American Marine stuff is completely forgien to me.
My Scarab was running a single 7.4 MPI 310hp which pained me as my previous boat had two 5.7 twin turbo motors and wanted to go down a similar
route so when I saw some value in the form of a low hour Mercruiser (Forged pistons, steel crank and low compression)502 Carb engine 415hp
which had been fitted with a Cutler EFI system 1000CFM (similar to Holley), MSD 6M-2, Mercruiser Thunderbolt IV Distributor and a set of exhaust headers I took a punt.
I then acquired an old school Gale Banks Stage Three Twin Turbo Setup. which consisted of 2 Gale Banks Exhaust Manifolds,2 Water Cooled Turbos and 2 Intercoolers.
There currently isn't the ability to control boost as it simply is preset via a hole in the exhaust side that allows gasses to bypass the turbo. From what I can find
out the system runs about 8psi stock and some people have restricted the bypass to increase up to 12psi. I can block these off and weld in some external wastegates if need be.
Here are two links to similar set ups:
http://www.performanceboats.com/part...turbo-kit.html
https://www.flickr.com/photos/menard...7616396786774/
https://www.flickr.com/photos/menard...7619340912710/
My current thoughts are to ditch the outdated Cutler EFI ECU and replace it with Holleys HP EFI (550-604) and run some bigger injectors and to remove the throttle
body and mount the intercooler on top of the inlet manifold and fit the throttle body where the carb would sit?
Is this a set up that would work anyway well? I really need to know what approximate power level these engines can run safely in stock form so that I can match the correct
injectors and to get the correct GPH fuel pump etc. I estimate a figure of about 700hp would that be a fair assumption?
Again I have no idea about American products and don't know if my existing Distributor and MSD ignition box me up to the job? are they standard
block connections that are plug and play with the Holley 550-604 kit?
Would I have a worthwhile benefit from sticking in a set of cams and rockers while the engine is out of the boat?
I know I'm probably going to be told to ditch the old kit and get a procharger but I just like the turbo idea.
Any advice or guidance as to how I would best set this up to maximize its potential on a reasonable budget would be greatly appreciated.
Many thanks from the Land of Eire!
Jay
10-31-2014, 10:57 PM
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i had one of those engines and i removed the orifice and replaced it with a smaller one.the darn thing went from 8 to 22 lbs.i was running 110 octane fuel in it.i never ran it on a dyno but im sure it made over 900 hp.i ended up selling it to a buddy who started a car project with it.he kind of lost interest in it and never finished it.he recently sold it to another buddy and i,d say it will be running in a year or two.if i still had that engine i would plug the internal waste passage and install a waste gate so i could adjust the boost,i would also run it on e85.
11-01-2014, 05:46 AM
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i had one of those engines and i removed the orifice and replaced it with a smaller one.the darn thing went from 8 to 22 lbs.i was running 110 octane fuel in it.i never ran it on a dyno but im sure it made over 900 hp.i ended up selling it to a buddy who started a car project with it.he kind of lost interest in it and never finished it.he recently sold it to another buddy and i,d say it will be running in a year or two.if i still had that engine i would plug the internal waste passage and install a waste gate so i could adjust the boost,i would also run it on e85.
Yes I think the wastegate is an absolute must. was your engine modified or stock? Did you run it on carb(s)?
11-01-2014, 06:19 AM
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You are more likely to find people that have used that setup over on performanceboats. These are generally reserved for jet boats and v-drives with open engine compartments, Unless you have a pair of water cooled turbine housings.
11-01-2014, 10:01 AM
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Yes I have read a lot of stuff on their forums as well, my Turbo housings are watercooled. no harm to ask the same question there also. thanks
11-01-2014, 12:20 PM
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I know I'm probably going to be told to ditch the old kit and get a procharger. Quote
In the long run I bet you will be miles ahead in money and time just going to a supercharger kit from Whipple, procharger or the one I like is Vortech.
Fabrication, electronics and tuning while trying to build an older twin turbo onto your 502 will be a big big job, just my two cents worth of input.
In the long run I bet you will be miles ahead in money and time just going to a supercharger kit from Whipple, procharger or the one I like is Vortech.
Fabrication, electronics and tuning while trying to build an older twin turbo onto your 502 will be a big big job, just my two cents worth of input.
11-01-2014, 12:34 PM
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Do you by have any pictures online or thread about your boat?
11-01-2014, 12:51 PM
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In the long run I bet you will be miles ahead in money and time just going to a supercharger kit from Whipple, procharger or the one I like is Vortech.
Fabrication, electronics and tuning while trying to build an older twin turbo onto your 502 will be a big big job, just my two cents worth of input.
Fabrication, electronics and tuning while trying to build an older twin turbo onto your 502 will be a big big job, just my two cents worth of input.
The entire kit I have bolts directly on, the intercooler bolts onto the cutler efi inlet manifold and the throttle body fits straight onto the carb mount at the turbos.
the only real expense will be upgrading the fuel system which has to be done regardless and then the updating to Holley EFI and the addition of a wastegate system.
Mapping her wont be an issue as I have experience on some high horse power cars.
Although I think there will be plenty more expense for an out-drive if she makes anything like the 1000hp like Phil's.... I'm sure i'd get over that expense though ;-)
