98 7.4 mpi ???

[fctyson0]

hello everyone can you tell me how i can tell the hp of a 7.4 mpi merc from the factory in a 98 crownline 226ccr?i dont think its a mag but wish it was.what can i do to get some more hp out of the 7.4 mpi?it seams a little small for this size performance boat.

 

[Bondo]

Re: 98 7.4 mpi ???

Ayuh,... How Fast do ya wanta Go,..??
How Deep is your Checkbook,..??

It's around 330hp...

 

[fctyson0]

Re: 98 7.4 mpi ???

what do you think the top speed of this boat is?its a bravo3 duo prop.i was thinking 50 mph but would love to see 55ish and want it to get out of the water.my brother has a 23ft rinker with 350 mag 300hp that is around 55mph so would like to be somewhere nere there

 

[fctyson0]

Re: 98 7.4 mpi ???

my other question is,should i hold out for a 7.4 mag 385hp?of the engines what one has been know to be a better engine over all?

 

[fctyson0]

Re: 98 7.4 mpi ???

anyone?

 

[Bondo]

Re: 98 7.4 mpi ???

Ayuh,... With a smaller barge,+ a Bigger motor, you should be able to Whip your Bro the way it is....

 

[fctyson0]

Re: 98 7.4 mpi ???

the boat i am looking at is 4 feet longer and almost same hp
heres another question,i am also looking at a 98 formula 252ss with 7.4 mpi motor.the owner has no idea if its 310 or 330 hp but says it will do 60 with 1 person.(prob dreamometer)also he said it has thunder header exhaust that you can screw on to make quiet.i realy want to make it a silent choice but not sure how much to change over.

 

[Philster]

Re: 98 7.4 mpi ???

50 ponies are worth about 3-4 MPH.

You're gonna get a headache trying to figure out top speeds because of all the variable (prop, prop type, number, drive/type).

Generally...

330 HP in a 24-26 foot deep V is worth 53-55 MPH. Downhill, maybe 58.

310 HP is worth about 50-52. Downhill, maybe 55.

When you flirt with 400 HP in those hulls, you can play over 60. Downhill, maybe 65.

7.4 MAG @ 385HP: Best way to distinguish it from the other 7.4L engines is that it has rectangular port heads and a high performance camshaft. They are the same heads that are used in the 8.2L 502 cid engine. The engine has a 1 piece rear main seal, roller camshaft.

7.4 MPI: This long block engine was used only with a General Motors installed multi-port injection (MPI) fuel delivery system. The long block utilizes a 1- piece rear main seal, roller camshaft, and oval port heads. The engine is rated at 330 hp but is not an actual produced power number. The actual horsepower value is about 305 hp.

7.4L 330hp 1987-2002: This long block engine was used with a 4 BBL carburetor, EFI (throttle body), and a Mercruiser factory installed multi-port injection (MPI) fuel delivery system. It has a 1 piece rear main seal, roller camshaft, and oval port heads.

How's that headache doing?

 

[fctyson0]

Re: 98 7.4 mpi ???

the boat in question is an 98 formula 252ss with 7.4 mpi duo stock stainless props.

 

[Philster]

Re: 98 7.4 mpi ???

See my edited post above!

 

[Philster]

Re: 98 7.4 mpi ???

I guess what I am getting at is that you and the bro are dealing with 7.4 liter Mercs pumping out the same HP.

They were advertised as 330 HP at one point. However, not unlike so many other engines in the 80's and 90's, they were restandardized to a lower number. Same engine, but different techniques to record the HP. They make about 300-310 HP. Heck, you will still see dealers, spec sheets and blah blah blah going on about 330 HP, and then you get one when the number was revised and 'bam', you feel like your manhood got smaller 'cause you got 305... 310, etc.

Now... the MAG jumps to 385 (and that is after the revisions).

For example, Ford dropped it's HP rating on the 5.0 engine in the 90's (maybe 80's) from 230 (maybe 225) to 215. Same engine. Same power. Just a new technique for recorded max HP. I believe Toyota was recently challenged to deflate some of their numbers, too.

 

[Bondo]

Re: 98 7.4 mpi ???

also he said it has thunder header exhaust that you can screw on to make quiet.i realy want to make it a silent choice but not sure how much to change over.

Ayuh,.... Generally speakin',.... Exhaust for a boat is Expen$ive,...
Everything your talkin' about is Cu$tom, Aftermarket,...
That alone rai$e$ the price$ to the $trato$phere,...

There's New,... Used,... 'n Do it Yerself stuff out there,... Look around...

 

[Philster]

Re: 98 7.4 mpi ???

the boat in question is an 98 formula 252ss with 7.4 mpi duo stock stainless props.

55 MPH boat at WOT when hitting the max operating RPM range.

Might have to lean on her to make it happen.

 

[fctyson0]

Re: 98 7.4 mpi ???

ok how about this?is there anywhere the hp raiting can be found on the motor or anywhere else?i am not looking to get the fastest boat out there i just want a boat that will do around 55mph and have no trouble getting out of the water with a bunch of ppl in it so thats why i realy want at least 330 hp and not 310.i would realy love 385 but cant find 1 in my price range

 

[fctyson0]

Re: 98 7.4 mpi ???

my bro`s oat that we are compairing to is a 23ft rinker with 350 mag 300 hp.

 

[fctyson0]

Re: 98 7.4 mpi ???

so if i am reading this right almost all of the 7.4 mpi`s are about the same hp310-330 depending how they are rated?realy no diff in hp between them?

 

[Philster]

Re: 98 7.4 mpi ???

Bingo.

BUT.... When in doubt, just get newer. Each year the HP might be tweaked up by a few ponies do to slight engine mods (better polished intake runners, minor crap), but they don't go ape-***** and redo tests and standards to show the new engine makes 2 HP more.

Look at it this way. Say a 1992 engine is rated at 330. Later, with revised testing methods, they re-publish the data on a 1999 version and it's rated at 310 in 1999. No one said the 1992 engine was now 310HP. The 1999 engine is now spec'd at 310. The 1992 engine, if it could be restandardized, might record 303 with the new testing methods.

Pop any Tylenol yet? Advil?

 

[fctyson0]

Re: 98 7.4 mpi ???

hate to beat this to deth but is the mpi much better then the efi?should i hold out for the454 mag?is it worth it?

 

[Philster]

Re: 98 7.4 mpi ???

MPI is definitely better than EFI.

Should you hold out? You're gonna need to decide.

I'd say the MAG is worth 50-55 more H.P. and that's 4-5 MPH +/- an MPH. Probably 5% better fuel efficiency even with the greater HP.

 

[fctyson0]

Re: 98 7.4 mpi ???

i am having trouble finding a boat in my area with this motor.i know they are out there but not in my price range and type boat.