Mercruiser engine questions
 

I am looking at a couple of older boats both with 454 mag engines but cannot find accurate information on what HP each engine is rated at. The first boat is an 89 with twin 454 mag engines and the second is a 90 with twin 454 engines. Any help or links to a sight that have the information would be appreciated.

Thank you!

fixx
 

if its a carb engine its 365 hp,if the valve covers are finned and with a trs drive could be 420 hp,if it has efi then its 385 hp..

That is what I had thought but recently I have found information that made me question it. I was hoping to find actual mercruiser information.

The early 454mags with Alpha drive packages were 330hp.

I believe that would be 86-87

What boats are we talking about here? It might be easier to look up the original manufacturers engine options, but then again being a 89 or 90 the engines might not be original..... then who knows

[my 454 mag mpi,s are 385 at the prop,


QUOTE=JBA;3913813]I am looking at a couple of older boats both with 454 mag engines but cannot find accurate information on what HP each engine is rated at. The first boat is an 89 with twin 454 mag engines and the second is a 90 with twin 454 engines. Any help or links to a sight that have the information would be appreciated.

Thank you![/QUOTE]

The first boat is a 1990 320 Black Thunder with twin 454 mags and Bravo drives all stock.
The second is a 1989 311 Formula with twin 454 mags and Bravo drives all stock.

Is there any actual Mercrusier information or website that I could look at to see what engines were offered in those general years? I am undecided on what boat to go with and also I am not limited to those two just in case anyone knows of another candidate to look at similar to the two I have already listed.

Those should be the 365hp 454 Mags then and they are rated at 350hp at the prop.

+1

Anything mercruiser built from 1988: 454 MAG and Bravo would be rated at 365hpat the crank and 350 at the prop. IF its a 7.4 litre and Bravo then its not the mag motor which means its 330hp at the crank and 310 at the prop.
--IF it was a 1987 vintage then you would see 454 mag but would have an alpha drive and be rated at 330/310

Old wellcraft sales brochures list the 7.4 330hp as 295hp at the prop and the 454 MAG 365hp at 360hp at the prop. Not arguing just saying that prop shaft hp numbers tend to vary depending on where you look. One thing for sure is the 365's are runners and the 330's.....well not so much

my 91 454 MAGS carbed are listed at 385 per the manufactures spec sheet from fountain.

Merc never made a carbed 454mag with 385hp. The carbed 454 mags were 365hp and the carbed 502mags were 390hp.

then maybe fountain did something, because their build sheet I have says 385, if you go to nadaguides it says stock equipment is 385 and when my insurance rand the sn of the boat they told me it had 385hp engines.

My point exactly! But I agree with Griff the 385hp was the later 454 Mag MPI with 385hp at the prop. I would guess the NADA guide made an error.

Close.
The 1989-1991 454Mag carb was 365/350.
The 1990-1991 502Mag carb was 410/390.

As far as the Fountain with 385hp 454Mag, it's a typo. Period. Fountain did not do anything to the motors to change the manufacturer's hp rating.

yeah I dont know, it might be. everything Ive had and even when people worked on them said their 385hp, so who knows, not like the 40hp difference probably makes a difference either way. I was thinking maybe the gill exhaust helped but I doubt it as its still manifolds on there vs headers. It just seems odd multiple places all say 385

maybe your carbed mag 454,s make 20 hp more than all the rest of them because you used 92 octane fuel,maybe reggie tested them that way,il bet he dyno,s every merc engine they installed in their boats.:party-smiley-004:

Gil manifolds DO help.
They probably are good for 10hp on a 454 Mag, and maybe 12-14hp on a 502Mag.

That puts your 454 Mags at maybe 375 instead of 365, but it technically doesn't change the ENGINE RATING.

Not sure where you're getting the 40hp difference, though unless you're counting the drop from crank rating to prop rating.

It's really irrelevant if you plan to add hop up goodies. Once you change the cam, do some port cleanup on the heads, bore notch the cylinders, and zero deck the block you're going to be well over 400-430hp. You have a good motor to start with.

Just be glad it's not the 330 version, which has weaker bottom end and poor flowing heads.

Probably best to grab some serial numbers so you can know for sure.

i have twins so thats why i said 40hp

I have them, also going to do a double take of the fountain build and inspection sheet I have when I get home.

Like I said do a nada guide run on a 91 fountain fever and it shows 385hp. I guess if the Gill added 10 hp, its possible 10hp might have came from somewhere else.

350hp prop according to the Mercruiser brochure I have in my hand.

http://www.boatfix.com/merc/Bullet/91/91_16.pdf


Case Closed! This is straight from Mercruiser. Prop HP is 350 on 454 mag/bravo

Ok i looked last night at the performance sheet the day the boat was ran, actually had a time, date, and test drive Actually had Reggies signature there, for those making jokes. It did say 365hp for each engine, so the case is now closed. But I find it funny how Nada, insurance keeps saying their 385s.

It all depends on the year, the 454 mag was 385 later.

I doubt the data entry geeks for the NADA database are mercury engine experts. I have noticed other errors on the NADA website and unfortunately this is the information that the insurance companies have to work with

yeah i doubt their pricing as it is. If i check my 91 it says 17k for the thing, and I dont think you could fine a running fountain for under 20

Hahaha agreed. Now this topic sounds like it could be the start of an interesting thread.

as boats get older the disparity in pricing gets worse. I think its understandable to a point as boats are not like cars there is millions of them like cars so its hard to get a good base line, and as a model gets older, there are even less to judge. But I have found as boats gets to be ten years old and older the pricing is all over the place.

Before my fountain i owned a crownline nada said it was worth 5500, but crownlines the same age were selling around 10. First guy comes and playes the whole nada game and offers 4500, I tell him go look on the market, and tell me if you can find a crownline or other like brand the same size in this shape for 4500, he scoffed and walked away. Same night another guy game offered 9, and it sold. So Im not a big fan of Nada. I think it offers a starting place, but I usually search 2-3 other like boats in the area and get my price.