EYEBURN

my 454 from 1998 is a carb motor. so i think, carb or mpi, isnt determined by year! with the rpms and props, it sounds like a 330hp 454.
does the intake manifold look REAL flat below the carb? can you find the serial number, mine was on the tstat housing. maybe you can identify from that????

groundsfordivorce

I have had a real problem finding the serial numbers. I have looked all over the motors, the top cover of the engines that the serial numbers were stamped in were gone before I got the boat . I finally got mercury marine on the phone and we referenced the numbers just below the head on the left side of the block to them and they told us the engines ( or the blocks)were 454's .

pwam1

There were some carbed 454s made in 98 as well as mpi.
If it is an mpi, see where the intake air filter is located. If it points to the front of the boat, it is a 310 hp. If it is on the starboard front corner and ponting to starboard, it is a mag 385 hp.

JasonSmith

Casting numbers on the heads will be under the valve covers. The ones on the block are at the rear on the back.....if I rember right. The "litre" value is on the side of the block at the rear. 7.4L for 454 & 8.2L for 502's.
Borders book store has books on BBC'c that will give casting #'s & where to find them & what they mean.
I also have one. Find some numbers & post them. You will probably have to pull the engines out & take them apart to really figure out what they are.

groundsfordivorce

the motors are efi but I don't think they are mpi's I beleive they are the 310 hp 454's but friends say they have to be the HO454 because the boat at WOT does 60 mph. they say if they were the 310 hp it wouldn't do 60

groundsfordivorce

My main concern is what the value of the boat would be with "fresh repowered 502's with 30 hours on them" <quote from his ebay ad, compared to 454's with efi and more than "30 hours on them" I think the guy was lying through his teeth he needed the money and he was big into ebay buying and selling cars through e-bay.

JasonSmith

Do your motors look like this? If they do they are the MAGS (385) if they have a plastic cover they are the 330 Hp motors.

snielsen

is not a mag for sure---you said it redlines at 4400-4600rpm. its not a mag for sure
60 with that power set up is about right on that size boat

JasonSmith

Dude, that is not true. If the boat is overpropped it physically can't turn the propellers past that RPM. There are so many unknowns in this deal you simply can't determine the HP by the RPM levels obtained with the current setup. What is the gear ratio in the drives? Let's say it has 1.36's in the drives. The propeller pitch would have to be in the 21" range. If it was propped thinking the drives had 1.50's in them the wheels should be 23-25's (assuming the wheels are 3 blades). The boat would be a dog with big wheels on it. Low RPM, poor planing, poor top end.
If we know for certian that the gear sets are 1.50's then look at propeller pitch. Is it right???
I still say take the boat to a professional shop and have them do what they do best.

snielsen

your right jason---i was just saying there would have to be alot of thing out of alignment for twin mags to only push that boat to 60 ( you would think upper 60's at least) i've had non mag 454's in the past , but anyway its still hard to imagine geeting screwed like that....that is such a GRIZZLEY situation good luck

lets us know how it works out!