mercruiser 5.7 compared to 5.7 magnum?

[doc_texoma]

Greetings...

I'm about to buy a Glastron CSS19 (1989) heap that comes with motor and outdrive.. For the money I am 100 percent certain that the block is going to be cracked, rusted out, whatever... But I know its a 5.7 magnum... I know/think after certain years that being a magnum meant it was MPI fuel injected.. I am unsure of what years this included and am unsure of any other differences. Can someone provide me with some insight to the differences assuming the 5.7 magnum is a 1989 model?

I've done some googling and don't find anything terribly definite..

TY

 

[CampbellCarl]

I think the standard was rated at 260hp and the magnum was close to 300hp, maybe 290 or so.

 

[3queens]

If my memory serves the magnum has a little more HP and a tuned port injection
The standard 5.7 had a throttle body injection

Give a few peps will chime in

Sun still out and 85 here
Peeps are still boating and swiming

 

[Backlash]

This may not apply to the earlier models, but at some point during the 90's, the 5.7 was rated at 260hp and came with the Alpha drive. I heard this was also a 2 bolt block. The 5.7 Magnum was fuel injected and rated at 300hp. This motor typically came with the Bravo1 drive and I believe it was a 4 bolt block. I think there was a difference with internals being forged vs. cast. But I'm not positive this applies to the late 80's motors.

Henry

 

[doc_texoma]

Ok... Excellent information.. The guy keeps on talking about it being a "290" .. I've never had a magnum before and again the results on google weren't terribly informative... I doubt its going to matter as cheap as I'm getting the boat..

Who knows.. Maybe it wont be cracked..

Thank you for the replies thus far..

 

[Deja_Vu]

Take a look at this link. Lists the engine models by serial number.

http://www.mercruisermotor.com/V8SBMOTORSB.html

 

[Trash]

Greetings...

I'm about to buy a Glastron CSS19 (1989) heap that comes with motor and outdrive.. For the money I am 100 percent certain that the block is going to be cracked, rusted out, whatever... But I know its a 5.7 magnum... I know/think after certain years that being a magnum meant it was MPI fuel injected.. I am unsure of what years this included and am unsure of any other differences. Can someone provide me with some insight to the differences assuming the 5.7 magnum is a 1989 model?

I've done some googling and don't find anything terribly definite..

TY

First off, if you get the serial number off the motor that will tell you the most.

I don't believe the 5.7 terminology was used in 1989 for the small blocks. We all know the basic motor as a 350 cid small block Chevy that has had various MerCruiser names over the years. Sometimes the name was attributed to HP rating, sometimes not. 1989 was not a MPI or TBI motor. Later on the 350 began to get the label as 5.7 but was the same basic motor.

Now to your question at hand the biggest difference between a standard 350 and a 350 Magnum (or 5.7 and 5.7 Magnum) was typically a mild bump in the cam and perhaps compression. For the most part the differences were (are) minimal. I've heard claims of forged internals etc. From the Magnums I've torn down in the small block realm none were forged and none had 4 bolt mains. The Magnum monicker was never directly related to an MPI motor, but an MPI motor could be a Magnum.

It is most likely your block is a late model 1pc rear main seal, two bolt main, possibly hyd roller motor, but likely flat tappet with standard heads. It was likely 260 hp at the crank (235 hp at the prop). Shortly after that (1994 or so) the Magnums EFI motors had a slightly (and I mean slightly) bigger cam sometimes referred to the GM 395 cam with the hp upped to 265 but this was measured at the prop vice crank. 1996 Vortec heads came into play and most of the small blocks ran in the 300 hp range.

These motors were virtually unchanged over the years, with the biggest change being the addition of hydraulic roller cams and the Vortec heads. I would not worry too much about whether the motor is a Magnum or not. Since you are likely going to re-power or rebuild I'd spec out a motor and have at it. Best of luck.

 

[TPC]

I remember the most is they had better pull-your-skiers-up-hole-shot power if prop'd correct.
Just noticeable and worthy.

 

[Slippery]

Killed a lotta brain cells since the 80's so memory is a bit fuzzy

As someone already mentioned, the didn't have the metric name back then.

The 350 chevy with the alpha drive was a "260" and had a sticker that said so on the outdrive.

The SS drive which was essentially a crescent shaped alpha drive was introduced late 80's, maybe early 90's if memory serves but wasn't part of the "magnum" package.

The next step up was a "350 magnum". I seem to remember the up charge being in the neighborhood of $500.oo

I believe the flame arrestor had a few more "discs" to flow more air. I also believe the exhaust risers on the manifolds had a slightly less restrictive bend.

I also don't remember seeing any 350 mags with through hub exhaust, doesn't mean it didn't happen but I've never seen one.

I don't know when Merc started offering fuel injection, but don't remember it in the 80's. I remember replacing the metering rods in the Q-jet carb's to get a bit extra.

The cam may have been a bit more aggressive but I think the internals were the same. I think it was more of marketing gimmick than real performance gain.

Much like in 99 when Ford came out with the SuperDuty. The "Off Road" package was a $40.oo option which consisted of a sticker. We tried to explain it to customers who didn't believe us, especially if they'd been somewhere else and gotten a different story, and we finally would end up asking "Look, what do you really think you're going to get for forty bucks?"

 

[Chili Palmer]

I had a 99 Howard open bow sport with the 350 Mag MPI it was port fuel injected with 300 hp with the Bravo 1. It was ok, all trimmed out what felt real fast and at 61 on the speedo GPS'd at 47 mph. What a let down.

 

[77charger]

I have a 93 350 mag in my eliminator from the merc manual i have its 250 at the prop hp.My uncle had a chapparal with a standard 350 things i notice was mine has a hi rise manifold,afb type carb vs a standard manifold and i believe his was a quadrajet carb.

Pretty sure the hp was within 10 of mine though.not much different.

 

[GregG]

Model year 1996's changed over to the Vortec heads I believe.

 

[Trash]

Model year 1996's changed over to the Vortec heads I believe.

True, and the first real HP increase because of these Vortec heads. Cams were the same (except the Scorpion motors).

Interesting note, I tore down a 1995 Merc 350 Mag EFI / MP motor with Bravo drive rated 265 hp at the prop. Later got a small block out of a 2000-02 MasterCraft ski boat. This motor was rated at around 330 hp or so. BOTH motors had IDENTICAL cranks, mains, pistons, block, cam etc. Both were injected. The only difference were the heads (1995 had non-vortec, later motor had Vortec). Funny how they claimed some 60 hp difference. I believe the heads were worth 30 hp, but not 60-65 hp as the cam and rpm band was identical.

 

[AzGeo]

Merc offered '350 MAG' motors with Webber 4 bbl carbs, long before they went to any EFI . I would be more concerned about how 'rusty, stripped threads, warped, or cracked' the block and heads are, you can always up grade a small block Chevy as long as you keep the idle speeds down for the Alpha drive . (Bravo will handle 800 RPMs)

 

[GregG]

True, and the first real HP increase because of these Vortec heads. Cams were the same (except the Scorpion motors).

Interesting note, I tore down a 1995 Merc 350 Mag EFI / MP motor with Bravo drive rated 265 hp at the prop. Later got a small block out of a 2000-02 MasterCraft ski boat. This motor was rated at around 330 hp or so. BOTH motors had IDENTICAL cranks, mains, pistons, block, cam etc. Both were injected. The only difference were the heads (1995 had non-vortec, later motor had Vortec). Funny how they claimed some 60 hp difference. I believe the heads were worth 30 hp, but not 60-65 hp as the cam and rpm band was identical.

Very interesting. I never knew that and your right, that is a very steep pony claim.

 

[GregG]

First off, if you get the serial number off the motor that will tell you the most. It is most likely your block is a late model 1pc rear main seal, two bolt main, possibly hyd roller motor, but likely flat tappet with standard heads. It was likely 260 hp at the crank (235 hp at the prop). Shortly after that (1994 or so) the Magnums EFI motors had a slightly (and I mean slightly) bigger cam sometimes referred to the GM 395 cam with the hp upped to 265 but this was measured at the prop vice crank. 1996 Vortec heads came into play and most of the small blocks ran in the 300 hp range.

Best of luck.

Yep, you are correct. I believe that the very first Magnum EFI's were shipped as early 1994's. I thought however, that these 1994's Magnums were 250hp at the prop mated to the Alpha One drive UNLESS you ordered a "Tournament Ski" motor option which bumped the ponies up a bit. Why, I don't know.

 

[AzGeo]

I think there was a "320 HP MAG EFI" (racing model in black) before the production (black) EFI motors ever came out . Long in the past, I have worked on a Hallett that had two of them with Bravos, long long ago . The EFI intake looked just like the ones on the 454 and 502 Production motors (black) that came after them . Throttle body 90 degrees to the 'ram plenum' on the starboard side .

 

[Trash]

Yep, you are correct. I believe that the very first Magnum EFI's were shipped as early 1994's. I thought however, that these 1994's Magnums were 250hp at the prop mated to the Alpha One drive UNLESS you ordered a "Tournament Ski" motor option which bumped the ponies up a bit. Why, I don't know.

That is correct, but the Magnum EFI / MP motors ordered with a Bravo 1 drive or "Tournament Ski" motors came with a tunnel ram style intake (Scorpion motor predecessor), side mounted two stage throttle body similar to the big block EFI /MP 454 and 502 motors.

 

[GregG]

I think there was a "320 HP MAG EFI" (racing model in black) before the production (black) EFI motors ever came out . Long in the past, I have worked on a Hallett that had two of them with Bravos, long long ago . The EFI intake looked just like the ones on the 454 and 502 Production motors (black) that came after them . Throttle body 90 degrees to the 'ram plenum' on the starboard side .

These race 320HP Magnums would have been available from the racing division ONLY before 1994 AzGeo? Were they called Tempest? That might tie in to the Alpha SS production dates which I believe was '87, '88 and early '89.

 

[Trash]

I think there was a "320 HP MAG EFI" (racing model in black) before the production (black) EFI motors ever came out . Long in the past, I have worked on a Hallett that had two of them with Bravos, long long ago . The EFI intake looked just like the ones on the 454 and 502 Production motors (black) that came after them . Throttle body 90 degrees to the 'ram plenum' on the starboard side .

You're mixing two motors up. There was the 320 EFI back in the 80's (late time frame) that was a rare bird. The intake similar to the 454/502 motors with side mounted throttle body was on the 350 Mag/EFI Bravo 1 motors and Tournament Ski motors introduced in 1994. They were 265 hp at the prop. I've got one of those motors but its been tweaked a little.

The 320 looks like this:



The 350 Mag EFI/MP Bravo 1 looks like this:

 

[GregG]

Trash, what was the "Tempest" motor or am I far afield now from 350/SBC stuff?

 

[OCMerrill]

I have a 93 350 mag in my eliminator from the merc manual i have its 250 at the prop hp.My uncle had a chapparal with a standard 350 things i notice was mine has a hi rise manifold,afb type carb vs a standard manifold and i believe his was a quadrajet carb.

Pretty sure the hp was within 10 of mine though.not much different.

YES! I have a 1991 Merc 350 Mag in my Laveycraft Sebring. It has as you have described and is rated as propshaft HP. The 260 hp SBC which was very typical in nearly everything from early 80's to right around 1990 was rated at the crank.

My 1991 350 Mag is rated at 245 hp at the prop.

 

[GregG]

YES! I have a 1991 Merc 350 Mag in my Laveycraft Sebring. It has as you have described and is rated as propshaft HP. The 260 hp SBC which was very typical in nearly everything from early 80's to right around 1990 was rated at the crank. My 1991 350 Mag is rated at 245 hp at the prop.

Do you have a picture of that 1991 Magnum Carb?

 

[Trash]

Trash, what was the "Tempest" motor or am I far afield now from 350/SBC stuff?

Unfortunately I'm not that versed on the Tempest small block. I will share what I believe is correct, but take it with a grain of salt. Those motors were 1989 vintage and basically a Mercury 'blue' motor before they were 'blue'. Think HP series motors. Tweaked out small block EFI motor. Cam was bigger than the stuff you'd see today and the motor spun upwards of 5400ish. Not orbital by any means but more than typical. I believe the electronics were just not up to snuff and that was the Achilles heal of the motor. Other may have more accurate information. I would not waste time seeking one out.

 

[OCMerrill]

Do you have a picture of that 1991 Magnum Carb?

I will get you one today. It's a Weber that is basically a Carter AFB.

A link I had saved.

http://www.marinemechanic.com/merc/distributors/mercurymarine/sterndrive/gmblockcodes1.PDF

 

[GregG]

Cool, thanks. Your link has a lot of info and explains a lot .............

 

[HBCraig]

My Dad has a 350 Mag MPI in his 21'er. Outside of one water pump, it has been bullet proof. Well over 500 hours.

 

[doc_texoma]

Thanks for all of the replies... This guy told me "and this one has the good 5.7 liter in it - its the 280 version..>" I had always heard of 5.7's referred to as 260's - and I was wondering if it was the "magnum" moniker that was making him want to call it a "280"...

As some have speculated I have no hope really that this motor will run so it likely won't matter... I will know relatively soon.. Bringing the boat home next weekend.

And as of that time a new project thread will begin!!!! Hey at least the hull is in good shape!!! Comes with an outdrive too but again who knows what kind of shape its in.. we will see..

 

[OCMerrill]

The years prior to the Mag being fuel injected (1994 and older) are foggy at best.

I am going to get into the boat today and look at the casting numbers on mine and get a picture of the carb and high rise manifold but I have to say I don't think the mag offers much more in the way of power in 1991 anyway. Just how the power is rated.

I put an edelbrock cam in mine and jetted up the carb.

Getting parts and jets for the Weber Carb is real easy.

Here is another link....

http://www.carburetor-parts.com/Weber-Marine-Carburetor_ep_485.html

 

[BDMar]

True, and the first real HP increase because of these Vortec heads. Cams were the same (except the Scorpion motors).

Interesting note, I tore down a 1995 Merc 350 Mag EFI / MP motor with Bravo drive rated 265 hp at the prop. Later got a small block out of a 2000-02 MasterCraft ski boat. This motor was rated at around 330 hp or so. BOTH motors had IDENTICAL cranks, mains, pistons, block, cam etc. Both were injected. The only difference were the heads (1995 had non-vortec, later motor had Vortec). Funny how they claimed some 60 hp difference. I believe the heads were worth 30 hp, but not 60-65 hp as the cam and rpm band was identical.

Sterndrive models are rated at the prop as you said. Inboard engines are rated at the flywheel

 

[Trash]

Sterndrive models are rated at the prop as you said. Inboard engines are rated at the flywheel

Yes, I understand that and was a little hesitant to do that comparison simply because of that issue.

 

[GregG]

Sterndrive models are rated at the prop as you said. Inboard engines are rated at the flywheel

Yes, I understand that and was a little hesitant to do that comparison simply because of that issue.

I never knew that. Takes away the mystery of why the exact same motor's had different HP ratings :thumbup:

 

[GregG]

Unfortunately I'm not that versed on the Tempest small block. I will share what I believe is correct, but take it with a grain of salt. Those motors were 1989 vintage and basically a Mercury 'blue' motor before they were 'blue'. Think HP series motors. Tweaked out small block EFI motor. Cam was bigger than the stuff you'd see today and the motor spun upwards of 5400ish. Not orbital by any means but more than typical. I believe the electronics were just not up to snuff and that was the Achilles heal of the motor. Other may have more accurate information. I would not waste time seeking one out.

I asked around a bit. It turns out that the "Tempest" came just before the "HP320". Same motor, the only difference is the Tempest 300 was carb (84, 85, 86) and the HP 320 was EFI (87, 88, 89) and they were both considered race motors before there were true blue motors from Merc. The HP 320 EFI got a promo race bump because it was announced when the 2.5" shorter Alpha SS drive was introduced so for 87 and 88 that was the hot set up for SBC. In 1989 the BBC Bravo combo was introduced and the hot motor was the HP 370 and up. But I digress.

 

[Trash]

I asked around a bit. It turns out that the "Tempest" came just before the "HP320". Same motor, the only difference is the Tempest 300 was carb (84, 85, 86) and the HP 320 was EFI (87, 88, 89) and they were both considered race motors before there were true blue motors from Merc. The HP 320 EFI got a promo race bump because it was announced when the 2.5" shorter Alpha SS drive was introduced so for 87 and 88 that was the hot set up for SBC. In 1989 the BBC Bravo combo was introduced and the hot motor was the HP 370 and up. But I digress.

For some reason I attached the Tempest name to the 320 motor. Not sure why. I didn't really follow the motor/drive combos during that time frame. Regardless thanks for the correction.

 

[Norm]

I never knew that. Takes away the mystery of why the exact same motor's had different HP ratings

I still have an early 1987 Magic 23' with a 320efi and the short alfa drive with factory bullet nose. 100s and 100s of hours in fresh ans salt water without problems, including one upside down ephisode. Sitting in my barn now if you want any pics or measurements.

 

[wzuber]

I still have an early 1987 Magic 23' with a 320efi and the short alfa drive with factory bullet nose. 100s and 100s of hours in fresh ans salt water without problems, including one upside down ephisode. Sitting in my barn now if you want any pics or measurements.

Merry Christmas cap't. This is a old thread from 2015, not likely to get many replies. Good of you to offer though...

 

[HST4ME]

Early carb magnums had a "high rise" intake compared to the passenger car flat intake. The q jet was set up a little fatter. Hydraulic and roller lifter shared the same cam as the pedestrian 5.7.

 

[Orange Juice]

My Dad has a 350 Mag MPI in his 21'er. Outside of one water pump, it has been bullet proof. Well over 500 hours.

I’ve got a 1985 260 in my Eliminator. I’ve own it since new.
1200 hours on Original engine and out drive. Alpha drive has been rebuilt once…..resealed. Engine is still original. 2 carburetor rebuild.

As long as water stayed out of the block, you might be ok. Change oil, replace battery, check plugs and do a compression test. If that checks out, rebuild the carburetor, and service the out drive, including the gimbal bearing. Run it, and let it nickel and dime you into a reliable boat.

Hopefully it was winterized, or allowed to dry out, before winter.