marine power 454?

[nos1967]

Im very close to buying a 1995 ultra custom 19' jet boat that has a marine power 454 and a dominator jet. The guy is a firefighter and had to leave town in a hurry so i cant contact him to get the ID tag on the motor, but im trying to figure out exactly which motor is in it. with my research i found that marine power made 330, 390 and 440 horsepower 454's in the mid 90's. the boat is bone stock from ultra and goes 68mph....so im hoping it has the 390 or 440 hp motor. I cant imagine it pushin 68mph with 330hp. does anybody have any knowledge of these marine power motors?

[Legal Chemistry]

I have an MP book at home, I can get you more information (I have the 390hp MP)
Off the top of my head the heads will be stamped "hi perf" for the 390 (look through the oil filler) The 390 has the sport pac ignition. 8.8:1 compression. forged pistons w/slight dome. I'm not sure about a 440hp 454, I don't recall that. There there was a 502 w/400+.

[nos1967]

thanks for your help, do you know if the crank and connecting rods were forged or cast? im guessing cast...but hoping forged.

[Legal Chemistry]

That I don't know, you'll have to check with MarinePowerUSA. The 440hp bbc was carb-only if that helps.

[Beer-30]

The 330hp should be the same shortblock as a 310/330 mercruiser. The 390 would be a "454 Mag" mercruiser (same as). A 440hp would most likely be an "LS-6" from back in the day. They still sold LS-6 long blocks up through early '90s.
Long Block
620-454380
http://www.cpperformance.com/images/620-4543.JPG
Brand Name: General Motors
Brand New GM Marine 454 V8 392 Horsepower Long Block
* 392 HP @ 5200 RPM / 447 lb. ft. @ 4000 RPM (PFI)
* 1-Piece Seal
* 4-Bolt Main
* Rectangular Port
* Roller Cam
* 8 Quart Oil Pan
Must use an electric fuel pump.
NO - Intake, flywheel, or water pump
http://www.cpperformance.com/images/620-454380.jpg
Long Block
620-74330G6WRCVH
Brand Name: General Motors
GM Marine 7.4 Litre (454 CID)
305 HP @ 4400 RPM / 435 lb. ft. @ 3200 RPM (PFI)
1987-2001, 1-piece seal, 4-bolt main, oval port, roller cam, 8 qt. oil pan, must use electric fuel pump.
No intake, flywheel, or water pump included.
http://www.cpperformance.com/images/620-74425G6.jpg
Long Block
620-74425G6
Brand Name: General Motors
GM Marine 7.4 Litre (454 CID) 425 HP
1-piece seal, 4-bolt main, rectangular port, roller cam, 8 qt. oil pan, must use electric fuel pump, No - intake, flywheel, or water pump.

[rivercrazy]

I had the 390hp version of the marine power 454. Its a nice motor with forged parts including the crank, rods, pistons. It also has rectangle port heads and an aluminum intake manifold.

[nos1967]

heres what i got from the owner. model J4545-CAL, serial 15806, Block number TO3245XYB. just by looking at the numbers i dont see anything performance, but if the 340hp motor has forged parts too ill be happy with that.

[bp]

that's not a block number. look at the left rear of the block, just above the bellhousing, and you'll find the casting number. it will have 6, 7, or 8 numbers, but it will be ALL numbers. head cast numbers use the same type of system - they will be either 6, 7, or 8 numbers, ALL numbers, but you will need to remove a valve cover to see 'em.

[nos1967]

1011482 is the number on the back of the block, looking through the oil filler all i can see on the head is markv which i know is the year motor it is. It also has an aluminum intake, but i think all motors came with that. MP doesnt seem to have an active web site right now...

[Jetmugg]

Probably most important consideration is the heads. I had a Marine Power 454 (the 330HP version) in an open bow 19' Gullwing. It ran about 65 in stock form. The limitation was the "peanut port" heads. After 1 season, I popped for aluminum bowtie heads, higher compression pistons, and a 502/502 cam. After making only those changes, I ran a best of 83 mph.
SteveM.
PS - if it has the peanut port heads, it will probably only rev to 4800rpm or so.