2000 mercruiser 350 mpi modifications

[bannister]

Hello,

I live in Athens Greece and own a 2001 Doral 250SE fitted with a 2000 Mercruiser 350 MPI V8 coupled to a bravo 3 drive.
I am looking for more power out of it.
Is there something you can suggest that would not involve opening the engine or re-programming the ECU?

I am hoping for a 50 ? 60 hp gain.
any thoughts?

 

[Bondo]

Re: 2000 mercruiser 350 mpi modifications

Ayuh,... Be Happy with what you have, or replace it with a Big Block....

 

[bannister]

Re: 2000 mercruiser 350 mpi modifications

That is the point....
I was aiming for a 383 mpi.....but,
According to the latest law here in Greece (another stupid one) I can not replace the engine with anything bigger than 315hp that the boat manual says is the biggest installed by the factory......
Boat is 6500lbs dry....
My aim is not speed but getting out of the hole faster/easier and cruising at 3500 - 3600 with reasonable fuel consumption.

 

[Bondo]

Re: 2000 mercruiser 350 mpi modifications

Ayuh,... Like I said, Enjoy what you've got...

It's the Biggest power available, for what you've got...
A 383 will require a different 'puter...

 

[bannister]

Re: 2000 mercruiser 350 mpi modifications

different 'puter... ???? meaning?

would a cam and intake change make any difference and if yes, any suggestions?

 

[kewlkatdady]

Re: 2000 mercruiser 350 mpi modifications

puter=computer.

 

[Riegfrghtl]

Re: 2000 mercruiser 350 mpi modifications

May want to try 4 blade prop and trim tabs if you don't have these already!

 

[bannister]

Re: 2000 mercruiser 350 mpi modifications

Ah, ok....

No need for different 'puter then. I am looking for ways to make more low end power and torque from my engine...

 

[Bondo]

Re: 2000 mercruiser 350 mpi modifications

Ah, ok....

No need for different 'puter then. I am looking for ways to make more low end power and torque from my engine...

Ayuh,... The whole story is, If you change pretty much Any of the hard parts of the motor to Hop it Up,...
The computer instantly becomes obsolete, 'n won't run the New combination of parts...

If ya wanta go Crazy,...
Build a motor, 'n slap a Carb on it...

 

[acuraguy81]

Re: 2000 mercruiser 350 mpi modifications

You should not have issues with planning I have a 7500lb 262 monterey and plan real nice and fast even with out using my trim tabs. So check your prop pitch sounds like you need to drop a few.

 

[acuraguy81]

Re: 2000 mercruiser 350 mpi modifications

BTW I have a 1999 350mag efi bravo three with 26pitch props. can run 30mph at 3100rpm

 

[bannister]

Re: 2000 mercruiser 350 mpi modifications

I am running bravo three as well and 22 pitch props..........
What is your top speed and rpm?

 

[Don S]

Re: 2000 mercruiser 350 mpi modifications

The one detail you need to know, is the WOT rpm. That is the determining factor in prop size.

PS: WOT=Wide Open Throttle

 

[bannister]

Re: 2000 mercruiser 350 mpi modifications

I can run 4200 WOT max trimmed out at 30 knots
3500 trimmed out at 24 knots

 

[acuraguy81]

Re: 2000 mercruiser 350 mpi modifications

Yea that sounds odd. I have more boat and can plane better and more top speed. you should double check your gear ratio in that out drive too might be for a big block be 2.2 or 2.1?

 

[bannister]

Re: 2000 mercruiser 350 mpi modifications

my ratio is 2:20 and my Mercruiser mechanic says that this is the right one for a bravo 3

 

[daydreamer1252]

Re: 2000 mercruiser 350 mpi modifications

Just a thought....what kind of shape is the hull in? A bit (or a lot) of marine growth can go a long way to slow a boat down....lots of drag that has to be fed HP before the rest can be used to make speed....again Just a thought......

 

[bannister]

Re: 2000 mercruiser 350 mpi modifications

No marine growth at all.
Boat just got in the water a week ago with new antifouling paint, engine and outdrive serviced etc....
It is a 25 foot cruiser 6500 lbs dry

 

[Bondo]

Re: 2000 mercruiser 350 mpi modifications

I can run 4200 WOT max trimmed out at 30 knots
3500 trimmed out at 24 knots

Ayuh,... Yer Overpropped...

That motor makes it's big power at 4800rpms...

4200 rpms at wot is borderline Lugging it....

 

[Don S]

Re: 2000 mercruiser 350 mpi modifications

I can run 4200 WOT max trimmed out at 30 knots

There's your problem, you should be running 4400 to 4800 rpm at WOT. I thought your 22 props sounded a bit much for that size of boat.
You need to reprop and get your rpm up closer to 4800 and your boat act a lot nicer.