2004 Mercruiser 6.2 repower

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
Buddy's SeaRay 270SD has a 6.2 MPI/B3 setup.

he was out about a month ago and it wouldnt start when he was going to leave the Bar/Restaurant on the water.

he thought it was a bad starter. called Sea Tow, had his boat towed to his mobile mechanic. I asked if he was hydro locked or not, he said didnt think so, however mechanic would be looking at it.

the mechanic was busy and didnt get to the boat for about 4 weeks.

turns out it was hydro-locked.

and it sat......

and now it wont turn over.

He was quoted 12k for a new motor

Having the buddy work with the mechanic on deals, however i told him to get the motor yanked, a Michigan Motorz long block would be so much cheaper.

however he keeps asking if I would help him build a motor as he knows I have built a few strokers.....

Just awaiting the serial number to know what ECM is in there, and to determine which heat exchanger i will be putting on the motor. in addition to closed cooling, I plan on stainless risers.

Who does the best job at re-flashing the stock ECM's ?

I will be changing the cam profile, the intake runners, porting the heads, and changing slugs. So I will need an appropriate tune.

RPM will be higher, torque band will be fatter.

Pictures will ensue..... Motor coming out today, should be on engine stand by weekend.
 
Last edited:

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
Who does the best job at re-flashing the stock ECM's ?

I read the question but the answer is and is not simple. Being a 2004, I'm thinking 555 ECM and don't know of anyone that can do that. If its a MEFI then that can be done.

OBD can reflash and tweek the tune for more HP. Wipple has different stage tunes and some like them. It actually comes down to the best tune is the one that is done on the motor.

If its a MEFI, then pick up MEFI burn SW, AFR meter and O2 sensors
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
Thanks AD.... Been asking for serial number for the past day.

Buddy will be in Miami tomorrow, so hopefully the shop mechanic calls him with serial number.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Was it salt water Scott ? Is it defo a write off ? I’ve known loads of GM engines to take in water and survive it easily after a few oil changes. You know what caused the ingress ? The 6.2 to me has always seemed a little bit pointless. I’m amazed it was even allowed production being so close in power to the 350 mpi in power. Suppose like all strokers, it will have a little more torque. I’m now wondering if the ecu is even different from the 350. Certainly the 350 has a different ecu from the 305 mpi. Not sure about the 383.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
Stock 377 (6.2) is 320hp vs the 350 (5.7) at 300hp

A very mild build.

370hp is easy with a cam change, 420hp is easy with a bit of porting, increase in plenum volume and a few more RPMs

Not sure what lead to the water ingress. My guess the dry joint exhaust manifolds rusted thru
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Stock 377 (6.2) is 320hp vs the 350 (5.7) at 300hp

A very mild build.

370hp is easy with a cam change, 420hp is easy with a bit of porting, increase in plenum volume and a few more RPMs

Not sure what lead to the water ingress. My guess the dry joint exhaust manifolds rusted thru

Not so good if it’s salt.
Yeah. Only 20hp difference between the mpi 350 and 6.2. I’ve a cam in my mpi...I’m not sure it’s suited at all. Runs a bit lumpy low down the rpm and only really works at high rpm. Pretty sure it’s down to the fuelling not being able to be adjusted with that ecu. Always going to be a hit or a miss I’d think.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
Serial number is 0M604738

these are the ECM's listed

6.2-ECM.jpg

looks like the 555.....

also looks like Hardin Marine offers custom tunes
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
Pictures of carnage......

Andrey picked up the motor.....

Dave looked in the bores with a bore scope.....rust..... and what we will refer to as "fish sauce"

so off comes the Starboard side manifold.

0816191734_resized.jpg0816191737_resized.jpg0816191738_resized.jpg0816191735_resized.jpg0816191739_resized.jpg0816191734a_resized.jpg0816191751_resized.jpg0816191756_resized.jpg

Back to the fish sauce.....

notice the emulsion of stuff in the bores..... a mixture of sea water with a heavy dose of algae, oil, rust and aluminum corrosion..... while attempting to get the pistons to move with a dead blow..... we were covered with what Andrey and Dave are now calling "Fish Sauce"

This motor is a core..... at best

Now for the choices

option A - stock long block and new manifolds - lowest cost and fastest back on the water
option B - stock long block, HX cooling, revised plumbing - about $1000 more than option A, however not dealing with the single point drain and the rusty manifolds...... priceless.
option C - New GMPP block, new GMPP vortec heads, SCAT cast rotating assembly, coated clevite bearings, Comp Cams / Hardin cam setup, HX, mild bump in RPM to 5500..... about 380 prop HP
option D - Option C with Forged internals and a lot more fueling..... and the RPM limit raised - about 420prop HP

late yesterday option E presented itself.... a factory reman Mercruiser 6.2 with Fresh Water cooling for about the price of option B....


Will keep y'all posted....
 

Attachments

  • 0816191734_resized.jpg
    0816191734_resized.jpg
    445.5 KB · Views: 4
  • 081619164695HDR.jpg
    081619164695HDR.jpg
    331.9 KB · Views: 3
  • 081619164695HDR.jpg
    081619164695HDR.jpg
    331.9 KB · Views: 3
  • 0816191646.jpg
    0816191646.jpg
    413.1 KB · Views: 3
  • 0816191646a.jpg
    0816191646a.jpg
    380.8 KB · Views: 3

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
forgot to mention..... the plastic dizzy is broken....Mercruiser wants $900 for a $65 GM dizzy
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
following back around to this.

Andrey and the boat mechanic went round and round for a few weeks... the Mechanic didnt look at the boat for 6 weeks which is why the motor is now toast.

so after some back and forth........Andrey now has a brand new Mercruiser reman'd 383 with a 3 year warranty.

with the flames on the engine cover....

$11k and he is back on the water.

HX cooled was another $3k more, and a few weeks out. The Mercruiser rep was being a stickler that if we ad a HX after, the warranty would be voided. because in his words "its not a factory heat exchanger". and I tried to explain, that yes it would be, I am just cutting out the middle man and getting the HX direct from Alfa Laval at 1/3 the Mercruiser price

so needless to say, not building a motor for Andrey right now. however selling off his old 6.2 as a core.

After a few weeks, he is listing the boat for sale with a new motor, and a new interior....
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
With him selling the boat there is no reason to buy the HX from Merc, they (Merc) would dance out of any repair even with original buyer
 
Top