View Full Version : Horsepower Question
Greg Guimond
06-27-2013, 06:57 AM
This motor is either a 1997 or a 1998, can someone tell me what the horsepower would have been? Thanks
BUIZILLA
06-27-2013, 08:02 AM
purty sure it's 310hp
Ghost
06-27-2013, 10:16 AM
+1 on 310 (The higher HP 454s had a higher WOT RPM range).
biggiefl
06-27-2013, 12:42 PM
Being left hand and 600rpm idle could it be a FWC inboard with possibly higher hp? 600rpm seems a bit low for raw water and aren't O/D's counter rotation....I know the Alphas were.
Ghost
06-27-2013, 12:52 PM
Agreed the LH smacks of inboard, but I don't think more HP (Other than the HP measurement spec maybe being different for inboards.) I believe my 310 horse Volvo 7.4 idled at 600.
biggiefl
06-27-2013, 01:05 PM
Quick question....1994 7.4L Bravo I think was 300 or 310hp back then....what was rpm range? For some reason I am thinking 4800 but now I am not sure and can't find crap on Bing.
BUIZILLA
06-27-2013, 04:10 PM
I had this exact engine in a 1995 252BR Formula with a B3
310hp, rev limiter was hard set at 4700 (confirmed :smile:)
they need to be wheeled to 4500-4600..........
Greg Guimond
06-29-2013, 05:00 AM
+1 on 310 (The higher HP 454s had a higher WOT RPM range).
Thanks Ghost, it looks like this is it .........1999 - Bravo drive, 7.4MPI, 310hp, 454cu. in. fuel injection - 9.3:1comp...........although I'm not sure why it would say LH on the tag.
Greg Guimond
06-29-2013, 05:10 AM
purty sure it's 310hp
Two new big block models:
7.4 L MPI – Bravo 1, 2 or 3 models (310 pshp/4200-4600 rpm) and Inboard models (310 pshp/4000-4400 rpm).
Uses the GM L29 base engine. This engine was designed for torque, not high rpm horsepower.
GM multi-port fuel injection system. 75mm throttle body. GM lower intake and plenum.
GM fuel injectors and rail. GM fuel injector harness. MerCruiser only adds elbow to
turn throttle body to front of engine to allow water cooled exhaust manifolds to be
installed. This engine is basically a complete GM package.
MEFI 2 (GM 96 Software) ECM. Additional features and codes are now enabled. New
software for the DDT and Rinda tools is required.
Requires a new fitting to accommodate the larger GM fuel rail test port. See Service Bulletin 97-24.
454 Magnum MPI Horizon – Inboard (380 pshp/4400-4800 rpm).
Basically a regular 454 Magnum MPI with enhancements to increase durability and
extend service intervals.
Most service intervals are now 3 years (instead of 1 year).
Platinum spark plugs and hi-temperature spark plug wires.
Extensive use of EDP and ceramic coating.
Closed cooling standard with the new extended life antifreeze (5 years/1000 hours).
Constant-tension hose clamps and engine mounted freshwater flushing device.
High mounted starter and alternator. Stainless steel ground studs.
MEFI 1 (GM 93 Software) in a MEFI 2 case.
BUIZILLA
06-29-2013, 07:50 AM
the LH is a std. rotation engine, counter-clockwise rotation looking towards the flywheel from the back.... the RH was the opposite rotation version, my 28 Cary had LH and RH 454 engines made by Crusader, they were peanut port carbed 310 or 320's
the MPI Horizon 380hp had different larger port heads and intake, the 310hp had the peanut port oval heads (smallest oval port heads ever made for a BBC) and smaller port lower intake..
Greg Guimond
06-30-2013, 11:27 AM
Thanks BUIZILLA for the explanation. The more I think it through the more I'm thinking the best option is a stock 502 Magnum MPI. Here are the SB's for the 1998 7.4MPI, maybe it will help someone down the road.
Service Notes:
•
Only the 350 Magnum MPI and 7.4L MPI (L29) engines use true MEFI 2 (GM 96 software)
ECMs. All others engines use the MEFI 2 (GM 96) ECM case, but are loaded with MEFI 1
(GM 93) software.
•
If an Alpha throttle body injected engine is stalling when shifting out of gear, make sure the
new shift interrupt spring (24-45599-1) has been installed.
•
If a 1998 7.4 L MPI (L29) is whistling between 800-2000 rpm, replace the throttle body
gasket with 27-861518. This gasket has a “D” shaped hole in it and the words “this side
out” printed on it. The wrong gasket was used in production on Bravo’s (0L014226 and
below) and Inboards (0L002190 and below).
•
SB 97-14: Engine specifications for new 1998 models.
•
SB 97-21: Required ECM replacement. This effects 1998 350 Magnum MPI and 7.4 L MPI
(stern drive and inboard models). See bulletin for serial numbers. Calibration problems
with warning system (oil pressure). May also require moving the brown lead from J1-4 to
J1-6.
•
SB 97-24: Service tools. Heat transfer compound (92-805701-1) and new fuel pressure
gauge adaptors to work with the GM L29 fuel rail fitting.
•
SB 98-4: Electric fuel pump check valve sticking. Effects Cool Fuel models only. Caused
by new government mandated fuel detergent packages. Net result is no fuel from the
pump, even though it is “running”.
•
SB 98-5: Gasoline additives causing fuel system component problems. Effects all EFI models.
Similar to 98-4, but includes injector problems and recommendations for preventing
these problems.
•
SB 98-11: Required ECM replacement. This effects 1998 7.4 MPI INBOARD models only
(0L002006-0L007302). This does not effect stern drive models. ECM recalibration to
eliminate stalling when shifting into reverse gear.
•
PB 98-6 (Rev. 1/01): This is a PARTS bulletin concerning fuel system replacement parts.
VST top cover O-ring is now available separately (25-803831).
•
SB 97-20: Required fuel line replacement on Cool Fuel models. This effects a massive
number of 1997 and 1998 models. The fuel lines may fail, causing a high pressure fuel
leak or may collapse internally causing low fuel pressure above approximately 2800-3500
rpm.
Greg Guimond
07-03-2013, 04:29 AM
Is it unusual to find the earlier 502 MPI Magnum's with closed cooling? 25% of the factory production? Less? I know you can add it aftermarket but was wondering (very roughly) how often they were equipped this way.
I was thinking being an inboard it was a 330hp, did a little checking found out in 93 the did away with the 330 and went to 310.
Greg Guimond
07-10-2013, 08:22 AM
On the 454 Carb's motors (1989, 1990, 1991) the standard motor made 330hp correct? And then the only other option was the 454 Magnum which made 365hp? Thanks
BUIZILLA
07-10-2013, 08:26 AM
On the 454 Carb's motors (1989, 1990, 1991) the standard motor made 330hp correct? And then the only other option was the 454 Magnum which made 365hp? Thanks
I believe that was Merc's advertised numbers..
if it was an OMC they would have been 340 and 370 for the exact same engines, since OMC always one-upped the competition,,,,
Greg Guimond
07-10-2013, 10:33 AM
I believe that was Merc's advertised numbers..
if it was an OMC they would have been 340 and 370 for the exact same engines, since OMC always one-upped the competition,,,,
Thanks BUIZILLA, these are Merc's. Beyond the difference in horsepower, was the Magnum version a significantly stouter motor as far as internals?
BUIZILLA
07-10-2013, 12:03 PM
I believe the 365/370 engines were rect port heads and intakes and a different cam
the 330/340 was oval port stuff
the early 330's had log manifolds, later 330 versions had center risers, all the 340 versions had center risers
Crusader used the same oval port engine as Merc and OMC, and sold it as a 350hp, with center risers
biggiefl
07-10-2013, 12:06 PM
Not sure about rods but pistons were forged on Mags.
Greg Guimond
07-10-2013, 07:44 PM
Thanks guys for the info, appreciated.
joseph m. hahnl
07-11-2013, 07:25 AM
Thanks BUIZILLA for the explanation. The more I think it through the more I'm thinking the best option is a stock 502 Magnum MPI. Here are the SB's for the 1998 7.4MPI, maybe it will help someone down the road.
Service Notes:
•
Only the 350 Magnum MPI and 7.4L MPI (L29) engines use true MEFI 2 (GM 96 software)
ECMs. All others engines use the MEFI 2 (GM 96) ECM case, but are loaded with MEFI 1
(GM 93) software.
•
If an Alpha throttle body injected engine is stalling when shifting out of gear, make sure the
new shift interrupt spring (24-45599-1) has been installed.
•
If a 1998 7.4 L MPI (L29) is whistling between 800-2000 rpm, replace the throttle body
gasket with 27-861518. This gasket has a “D” shaped hole in it and the words “this side
out” printed on it. The wrong gasket was used in production on Bravo’s (0L014226 and
below) and Inboards (0L002190 and below).
•
SB 97-14: Engine specifications for new 1998 models.
•
SB 97-21: Required ECM replacement. This effects 1998 350 Magnum MPI and 7.4 L MPI
(stern drive and inboard models). See bulletin for serial numbers. Calibration problems
with warning system (oil pressure). May also require moving the brown lead from J1-4 to
J1-6.
•
SB 97-24: Service tools. Heat transfer compound (92-805701-1) and new fuel pressure
gauge adaptors to work with the GM L29 fuel rail fitting.
•
SB 98-4: Electric fuel pump check valve sticking. Effects Cool Fuel models only. Caused
by new government mandated fuel detergent packages. Net result is no fuel from the
pump, even though it is “running”.
•
SB 98-5: Gasoline additives causing fuel system component problems. Effects all EFI models.
Similar to 98-4, but includes injector problems and recommendations for preventing
these problems.
•
SB 98-11: Required ECM replacement. This effects 1998 7.4 MPI INBOARD models only
(0L002006-0L007302). This does not effect stern drive models. ECM recalibration to
eliminate stalling when shifting into reverse gear.
•
PB 98-6 (Rev. 1/01): This is a PARTS bulletin concerning fuel system replacement parts.
VST top cover O-ring is now available separately (25-803831).
•
SB 97-20: Required fuel line replacement on Cool Fuel models. This effects a massive
number of 1997 and 1998 models. The fuel lines may fail, causing a high pressure fuel
leak or may collapse internally causing low fuel pressure above approximately 2800-3500
rpm.
Nice bulletin :smile: alpha recall on a spring for the shift interrupter:propeller:
High speed/RPM miss on 350 mag 22zx:idea: (http://www.donzi.net/forums/showthread.php?68807-High-speed-RPM-miss-on-350-mag-22zx)
Greg Guimond
07-16-2013, 02:45 PM
This engine is a 1991, am I correct that the 454 Magnum made 365 ponies?
Greg Guimond
07-24-2013, 06:53 AM
The attached picture is evidently a 502 carb'd crate motor installed new in 2006 to replace a 1990 454MAG that came with the boat. The owner is saying he believes it makes an even 500hp on 89 octane. Does this sound accurate? Can anyone tell from the pic what goodies it might have that are perhaps better than a factory 502MAG. Thanks for any insights.
BUIZILLA
07-24-2013, 07:12 AM
I have serious doubt it even makes 400hp..... :wink:
Greg Guimond
07-25-2013, 06:49 AM
Bummer, what are the telltales?
Greg Guimond
07-28-2013, 11:01 AM
I have serious doubt it even makes 400hp..... :wink:
He is saying that it pushed his 22 Classic to 79 on GPS (1/4 tank of gas) with a Bravo I four blade 24" prop. What kind of horsepower would be needed to achieve 79 ?
Greg Guimond
07-28-2013, 01:01 PM
I also should have added that he is saying the top RPM is 5100
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions Inc. All rights reserved.