PDA

View Full Version : What available upgrades r there 4 a 7.4mpi 310hp?



IA26ZX
08-11-2010, 07:43 PM
I am a proud new owner of a 26ZX and extremely excited to be able to finally own one! The ride compared to my Crownline 225BR is unbelievable! The downside is that it only has the 310hp version of the 7.4mpi. I am planning on installing stainless headers and a K&N spark arrestor. Are there any other modifications that I can install other than a supercharger that will give me more horsepower without ruining the engine? Any help is appreciated.

mrfixxall
08-11-2010, 08:07 PM
I am a proud new owner of a 26ZX and extremely excited to be able to finally own one! The ride compared to my Crownline 225BR is unbelievable! The downside is that it only has the 310hp version of the 7.4mpi. I am planning on installing stainless headers and a K&N spark arrestor. Are there any other modifications that I can install other than a supercharger that will give me more horsepower without ruining the engine? Any help is appreciated.


theirs a mod that you can do to pick up 10 mph..Pull the engine and sell it as a complete drop in and find a 502 mag or a 500 efi,dont waste your time with that motor..It was built for one thing cruising and thats it!

Good luck
fixx

P.S. welcome to the madness :)

Cuda
08-11-2010, 09:36 PM
There are many articles on modifying that engine. None of them are cost effective and don't give the performance desired. The problem is the peanut port heads are the choke point. I had an 82 330 horse which was the last year if the large oval ports.

The Hedgehog
08-11-2010, 10:30 PM
What these guys said. They are dead on.

I love my 26ZX. It wakes up nicely with power. A 502 Mag is a good starting point. Beyond that, it only becomes more fun.

Dr. David Fleming
08-12-2010, 11:14 PM
IA - I just saw Tyler Crockett do a 500 hp hot rod on this engine - trouble was - the trouble.

This is what he did. Put a blower on it - A Whipple external blower (supercharger) - this blew the weak crankshaft and pistons in the engine. Soooo - they put new steel crankshaft and forged pistons on it. Thennnn - they were testing all 500 hp out on the St. Clair River - Anddd - they burned the pistons because the fuel injectors were too small capacity in the 310 hp version of the engine it went fuel lean. Soooo - Tyler put new pistons in it and bigger fuel injectors and Prestoooo - he done it!

Trouble is the guy could have sold the 310 hp for about $2000 and for another $10,000 to 20,000 could have had some real serious Merc power. I would stay with the 502 MAG MPI or 454 MAG MPI or similar carburated engines - which are almost a direct swap with most of your Mercruiser brackets and accessories, or go to Merc Racing 500 EFI - both of these power plants would not be too much for your Bravo I stern drive.

The Hedgehog
08-12-2010, 11:29 PM
IA - I just saw Tyler Crockett do a 500 hp hot rod on this engine - trouble was - the trouble.

This is what he did. Put a blower on it - A Whipple external blower (supercharger) - this blew the weak crankshaft and pistons in the engine. Soooo - they put new steel crankshaft and forged pistons on it. Thennnn - they were testing all 500 hp out on the St. Clair River - Anddd - they burned the pistons because the fuel injectors were too small capacity in the 310 hp version of the engine it went fuel lean. Soooo - Tyler put new pistons in it and bigger fuel injectors and Prestoooo - he done it!

Trouble is the guy could have sold the 310 hp for about $2000 and for another $10,000 to 20,000 could have had some real serious Merc power. I would stay with the 502 MAG MPI or 454 MAG MPI or similar carburated engines - which are almost a direct swap with most of your Mercruiser brackets and accessories, or go to Merc Racing 500 EFI - both of these power plants would not be too much for your Bravo I stern drive.

Have not heard that story yet, but don't doubt it. You can whipple it. It is not really the heads but more of the smaller margin of error from the cheaper innards.

Boosted motors like to flow but don't need to as much as NA engines.

Another vote for the Mag motor.

CJmike
08-13-2010, 12:36 PM
Get something in a pretty blue color and you should have the bases covered. 500 hp would wake it up nicely.

mrfixxall
08-13-2010, 01:15 PM
If you could chew this guy down it would make a nice starting piece :)

http://www.offshoreonly.com/classifieds/mercury_525_efi-o35413-en.html

Here's a screaming deal!!! http://stlouis.craigslist.org/boa/1885418754.html
The way the add reads he may take your plus some cash..

BigGrizzly
08-13-2010, 03:14 PM
I a.m staying out of this. My son did a wipple an d changed the heads-the real problem. and had hundreds of hours and sold it still running. Now I hate wipple.

The Hedgehog
08-13-2010, 03:44 PM
[QUOTE=BigGrizzly;574608]I a.m staying out of this. My son did a wipple an d changed the heads-the real problem. and had hundreds of hours and sold it still running. Now I hate wipple.[/QUOTE

As you well know, it is all in the setup.

BUIZILLA
08-13-2010, 04:50 PM
I love Whipple's...

errrrr, I mean wacky paddles.. :kingme:

IA26ZX
08-13-2010, 07:04 PM
Thanks for the help guys. I totally agree with something in a pretty blue color, but the checkbook does not. I talked with my Donzi dealer and he said going to the 454 mag will only gain about 1-2 mph. Not hip on that. I've seen different listings on the 502 mag for horsepower. What is a truthful number? I'm running a 4 blade 22 pitch on it now and running 58ish. Someone in the other room just said I don't need all that power but,but,but I WANNA GO FAST!!!!!!! :nilly:

mrfixxall
08-13-2010, 07:46 PM
Grizz,your sons boat was a 22 not a 26 zx,add a few more thousand pounds then throw boost at it and chances are it wont last long especially when theirs 3/8 connecting rods in the motor..

just my o2

The Hedgehog
08-15-2010, 10:32 AM
502 Mag would be a good base. You will see around 8 mph from that and it is a good base for mods.

My base engine is a 502 mag and the mods really woke it up.

blackhawk
08-16-2010, 10:06 AM
Thennnn - they were testing all 500 hp out on the St. Clair River - Anddd - they burned the pistons because the fuel injectors were too small capacity in the 310 hp version of the engine it went fuel lean. Soooo - Tyler put new pistons in it and bigger fuel injectors and Prestoooo - he done it!

That doesn't sound like Tyler.

Cuda
08-16-2010, 12:19 PM
That doesn't sound like Tyler.
I believe the HP 500 has a 502 Mag base.

LKSD
08-16-2010, 09:53 PM
I too agree that if it only has the 7.4 then don't waste your time with it. Go to a 502 or 540 if you are going to sell yours as a take out. That boat is a great ride, but it needs big power to get it cooking. Been there done that.. ;) If you would like to look in to it further feel free to give me a shout during the day.. :)

Also some playing with drive height & props could gain you some additional speed once you get the power you want. But doing a bunch of stuff to a plain 7.4 wont get you much. The money is better spent elsewhere.. ;)

Jamie / Lakeside Restorations