99 Mercruiser 250HP TBI Loss of Power - Repower 5.7 to 6.2 /Rebuild???

G

ghoover

Recruit
Joined
Aug 24, 2011
Messages
2
Hi guys,

I have a 99 251 proline a real heavy boat with all of my fishing gear auxilary trolling motor, fuel etc. Around 9000 lbs fully loaded had it weighed last year.

I have been experiencing major power loss over the past few years. This boat new was 4400 to 4600 RPM. It has a TBI 250HP Bravo III.

Now it feels like the boat is really laggy and slow, I am lucky to get 4000 RPM, sometimes I cant even get 3400 RPM if its loaded, then I change the fuel filter and I get some power back, usually up to the 4000 RPM. But never back to the original 4400 - 4600 RPM

This boat has always been run nearly full throttle to the fishing grounds and back and has approximately 670 hrs on the engine. The engine runs smooth starts smooth seems to run great but no power it seems.

I have tried different fuel additives even change the fuel filter and check for moisture but still cant find anything.

So 2 Questions

1) Is this a fuel problem or injector problem or some other problem? What should I check?

2) If i need a repower a)can I upgrade my longblock to a 6.2 and reprogram the MEFI chip? b) can i replace with a 5.7 block and change the injectors and reprogram to get 330 HP?

for the repower questions what must i do to make either work properly, I think this boat needs more than 250 HP and more torque, the 6.2 may be the way to go.

Thanks in advance for your help and advice
 
Tail_Gunner

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: 99 Mercruiser 250HP TBI Loss of Power - Repower 5.7 to 6.2 /Rebuild???

ghoover said:
Hi guys,

I have a 99 251 proline a real heavy boat with all of my fishing gear auxilary trolling motor, fuel etc. Around 9000 lbs fully loaded had it weighed last year.

I have been experiencing major power loss over the past few years. This boat new was 4400 to 4600 RPM. It has a TBI 250HP Bravo III.

Now it feels like the boat is really laggy and slow, I am lucky to get 4000 RPM, sometimes I cant even get 3400 RPM if its loaded, then I change the fuel filter and I get some power back, usually up to the 4000 RPM. But never back to the original 4400 - 4600 RPM


http://www.obd2allinone.com/sc/details.asp?item=mefitune

Give them a call, they are not novice in any way and very good with mefi....Your current setup is tuned very badly

This boat has always been run nearly full throttle to the fishing grounds and back and has approximately 670 hrs on the engine. The engine runs smooth starts smooth seems to run great but no power it seems.

I have tried different fuel additives even change the fuel filter and check for moisture but still cant find anything.

So 2 Questions

1) Is this a fuel problem or injector problem or some other problem? What should I check?

2) If i need a repower a)can I upgrade my longblock to a 6.2 and reprogram the MEFI chip? b) can i replace with a 5.7 block and change the injectors and reprogram to get 330 HP?

for the repower questions what must i do to make either work properly, I think this boat needs more than 250 HP and more torque, the 6.2 may be the way to go.

Thanks in advance for your help and advice
Click to expand...


http://www.obd2allinone.com/sc/details.asp?item=mefitune Give them a call you will be delighted





Custom ECM Tuning
We have the knowledge and ability to tune many different engine controller types. We can do E67, E38, LS1, LT1 and a variety stock Delphi ECM and PCM controller types on a mail in or in person basis. If you have a GMPP E67 controller for an LS7, LS3, or LS2, we can make changes to it, such as correcting idle speed issues. We also do aftermarket systems such as Accel DFI, Motec, Haltech, etc, if you are local in Southern California or if we are at your location. Call or email us for details.



Geez whats with the funny post???
 
T

TilliamWe

Banned
Joined
Dec 21, 2004
Messages
6,579
Re: 99 Mercruiser 250HP TBI Loss of Power - Repower 5.7 to 6.2 /Rebuild???

Is the bottom of the boat particulary dirty?
9000lbs, is that how much it's supposed to weigh?
 
Tail_Gunner

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: 99 Mercruiser 250HP TBI Loss of Power - Repower 5.7 to 6.2 /Rebuild???

Opps went a bit fast there for some reason i was under the impression you had done the upgrade already. Take a look at your injectors under a neon or led light. The spray pattern should be a heavy conical shape with no dripping..If there not well have them cleaned by a machine ... and new filtrers. From there work backwards next stop fuel pressure regulator and then the high pressure rail...Or maybe the injectors...high pressue line then the regulator...From there its the pumps and the tank...

Then theres the timing....
 
G

ghoover

Recruit
Joined
Aug 24, 2011
Messages
2
Re: 99 Mercruiser 250HP TBI Loss of Power - Repower 5.7 to 6.2 /Rebuild???

i will work thought the fuel system and injectors to see what i can get from that. i will have the injectors cleaned at the marina with their machine. change and gap new plugs.
the hull is clean, props were rebalanced and polished this spring, they look mint.

I will also check compression and timing.

but on the other note, can i change this engine to a 6.2l by buying a long block and just programming it?

how is this post funny? lol
 
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