142 supercharger on a stock 5.7 ?

[Junkyardroad]

My 1995 Donzi 212 has a Mercruiser 5.7/350, probably 260 hp. My favorite lake is at 6500 feet which really hurts power. The 142 Weiand supercharger is looking like a good option to restore some performance. (<100hp) The clearance between the blower snout and thermostat housing is questionable though, and Holley doesn’t appear to have any data about fitment. Has anyone done this?

The drive is an Alpha Gen II with a 1.5 SEI lower

 

[Scott Danforth]

First, please understand automotive vs marine requirements

Second, understand the limit of your alpha drive.

Adding a supercharger will require a different fuel system than what you have

Not to mention stock alpha drives are limited to 300 HP.

While you can add it. You must understand that the thermostat housing is the first of many many modifications.

At 6500 feet you are down 20% just due to altitude

 

[QBhoy]

First, please understand automotive vs marine requirements

Second, understand the limit of your alpha drive.

Adding a supercharger will require a different fuel system than what you have

Not to mention stock alpha drives are limited to 300 HP.

While you can add it. You must understand that the thermostat housing is the first of many many modifications.

At 6500 feet you are down 20% just due to altitude

Did they not mate big block 7.4’s to alphas at one point Scott ? I’m sure there used to be an old glastron in my yard with an alpha one or maybe even an mr1 with a 7.4 carb in it. Likely not a great idea though. Agree. I’ll have about the max for an alpha in my boat, but always a good idea to wind on the power, I think. Not that I have lots of power down low anyway

 

[Scott Danforth]

Did they not mate big block 7.4’s to alphas at one point Scott ?

yes, back in 1988/1989 only and they all broke and was a warranty nightmare for Brunswick.

 

[stresspoint]

guessing from the boat build year you have a carbed motor .
that said , IMO , it would be cheaper and more reliable with less modifications to get yourself one of those aftermarket fuel injection systems ,
try to get one with a user programable map that way you can get real time figures and you can play with performance tunes. .

i like your thinking , yes a super charger will serve the purpose but i think you will be digging a money pit to get it it work suitably.

 

[Scott Danforth]

guessing from the boat build year you have a carbed motor .
that said , IMO , it would be cheaper and more reliable with less modifications to get yourself one of those aftermarket fuel injection systems ,
try to get one with a user programable map that way you can get real time figures and you can play with performance tunes. .

i like your thinking , yes a super charger will serve the purpose but i think you will be digging a money pit to get it it work suitably.

only if you want to have your motor go lean. a few folks on here went the Sniper route and ended up taking out their motor

 

[QBhoy]

guessing from the boat build year you have a carbed motor .
that said , IMO , it would be cheaper and more reliable with less modifications to get yourself one of those aftermarket fuel injection systems ,
try to get one with a user programable map that way you can get real time figures and you can play with performance tunes. .

i like your thinking , yes a super charger will serve the purpose but i think you will be digging a money pit to get it it work suitably.

Apologies to jump on this. But do you have one in mind or that you’re aware of that can replace a stock 555 ecu?

 

[QBhoy]

yes, back in 1988/1989 only and they all broke and was a warranty nightmare for Brunswick.

Fair play. Not surprised to hear that.

 

[Scott06]

My 1995 Donzi 212 has a Mercruiser 5.7/350, probably 260 hp. My favorite lake is at 6500 feet which really hurts power. The 142 Weiand supercharger is looking like a good option to restore some performance. (<100hp) The clearance between the blower snout and thermostat housing is questionable though, and Holley doesn’t appear to have any data about fitment. Has anyone done this?

The drive is an Alpha Gen II with a 1.5 SEI lower

Did you consider a 383 swap? would give about 340 hp if vortec headed several folks on here successfully running those in front of alphas especially in lighter boats, and would likely be an easier swap

 

[stresspoint]

only if you want to have your motor go lean. a few folks on here went the Sniper route and ended up taking out their motor

that's interesting info , thanks for the heads up . i was unaware that the Holley snipper system caused lean problems with IO application's , lots of guys using them now days on HP automotive motors without issues .

obhoy , i was thinking along the lines of the Holley snipper ,to be honest , i would have no clue how to get it to work with the ECU you mention , but i am sure their are EFI wizz folks that would have it working in no time .

 

[Scott06]

that's interesting info , thanks for the heads up . i was unaware that the Holley snipper system caused lean problems with IO application's , lots of guys using them now days on HP automotive motors without issues .

if you read up on sniper weather it is automotive or marine some folks have issues setting them up. Its not that the system doesn't work, seems more like Holley oversells the self tune feature. Seems like some folks have to go download different fuel mapping from holley to get them to work right. Haven't spent much time looking into it as I prefer carbs... just would caution folks to really dig into it as it doesn't seem to be plug and play as they advertise

 

[stresspoint]

if you read up on sniper weather it is automotive or marine some folks have issues setting them up. Its not that the system doesn't work, seems more like Holley oversells the self tune feature. Seems like some folks have to go download different fuel mapping from holley to get them to work right. Haven't spent much time looking into it as I prefer carbs... just would caution folks to really dig into it as it doesn't seem to be plug and play as they advertise

i also prefer a well tuned carb over EFI when it comes to performance , I'm old school . .

my post was thinking along the lines of the amount of effort that the OP would need to put into getting a superchager to work properly at his altitude with a carb set up ,predicting jetting would be a nightmare.

if there was a a pre set map that Holley have already developed for the snipper , Op could plug and play and still retain his OEM HP or at least most of it and retain reliability .

 

[Scott06]

i also prefer a well tuned carb over EFI when it comes to performance , I'm old school . .

my post was thinking along the lines of the amount of effort that the OP would need to put into getting a superchager to work properly at his altitude with a carb set up ,predicting jetting would be a nightmare.

if there was a a pre set map that Holley have already developed for the snipper , Op could plug and play and still retain his OEM HP or at least most of it and retain reliability .

Even if there is a preset map based on air pressure , any engine will still be down on power at altitude. its not AFR that causes the power loss , its the lower O2 content in air. So you can get the AFR ratio right but you will still be down on power. Superchargers gained use during second world war to keep piston engine performance up at higher altitudes planes were flying at

 

[stresspoint]

Even if there is a preset map based on air pressure , any engine will still be down on power at altitude. its not AFR that causes the power loss , its the lower O2 content in air. So you can get the AFR ratio right but you will still be down on power. Superchargers gained use during second world war to keep piston engine performance up at higher altitudes planes were flying at

for the sake of the conversation regarding high altitudes and supercharging, ,correct me if i am wrong here , weren't those motors with superchargers mechanically injected , if so what type of system did they run , curiosity .

 

[Scott06]

for the sake of the conversation regarding high altitudes and supercharging, ,correct me if i am wrong here , weren't those motors with superchargers mechanically injected , if so what type of system did they run , curiosity .

out of my area of expertise

 

[Scott Danforth]

if so what type of system did they run , curiosity .

pilot turning knobs

 

[flashback]

pilot turning knobs

Yep they had to keep a close eye on manifold pressure and adjust the throttle accordingly, especially at low altitude..

 

[Scott Danforth]

Yep they had to keep a close eye on manifold pressure and adjust the throttle accordingly, especially at low altitude..

and EGT's which indicated AFR

 

[flashback]

And in the meantime fight the dang thing!

 

[nola mike]

only if you want to have your motor go lean. a few folks on here went the Sniper route and ended up taking out their motor

I think that was only one guy, and he lost his display while tuning the motor and ran it flat out anyway iirc