Mercruiser MX6.2 bravo 3 wont go over 4500rpm

[Justin Kennedy]

05 Mercruiser MX6.2 b3 runs well but wot only 4500rpm. (should be around 5200) Has cool fuel with both pumps inside. Fuel psi @ 38psi. Wondering if that could be the culprit. You notice a slight hesitation from idle to wot if you accelerate hard. Not so noticable if slowly accelerate. Very slight hesitation as you move to full throttle. Holds 4500 steady. On occasion, it will die as you move to wot, as if someone turned the key off. Restarts right away. Engine sounds good but definitely not developing full power. She has about 20hours on a major overhaul. Most componentrs are new. Has an electric solenoid anti siphon valve that I have bypassed for now. Fuel is clean.

 

[Scott Danforth]

your fuel pressure is a bit low. that would make you down on power.

 

[pmp1986]

your fuel pressure is a bit low. that would make you down on power.

Hi, Scott. Quite same problem. What fuel pressure should be for 6.2 as "fine"?

 

[alldodge]

The manual shows 43 psi at 1800 rpm.

Need to find out if its the pump, regulator or fuel system.

 

[Justin Kennedy]

I put the fuel psi gauge back on and ran it up to 1800rpm for several min. The needle bounces rapidly between 30 and 38psi. At one point it slowly went to 0 and stalled. I turned the ign switch off, then on resulted in 0psi. I never heard the low pres pump either. I repeated the process, and again 0psi. 3rd time and the low pres pump came on and pressured up to 35. Engine started and at 1800, needle bouncing between 30-38psi. Im wondering if the high pres pump is going bad. Typically I hear the low pump coming on, yet even still I have only 4500wot. Would the low pres pump cause issues at wot? My fuel line to tank is only about 18". Fuel system is clean, new filter etc. I cleaned the tank along with the longblock replacement.

 

[alldodge]

I'm thinking a bad connection, either on the relay, the relay it self or the fuel pump module.

Would help with your engine serial number, but since you have a Bravo drive you should have the Merc fuel module. The module has two pumps inside it, low and high. Both pumps should be running at all times when the motor is running

 

[Pete104]

20 hrs on the major overhaul?

Better check the fuel system closer.