Faulty fuel injector(s)?????

[sotaman]

I have a 1996 27' Dancer with a single 7.4 EFI, Bravo 3. I was having a severe problem with the boat bogging down and then surging. I would run it at 3000 RPM, getting to 25 MPH. Then she would just drop in MPH while the RPM stayed at 3000 with a surge here and there. Sometimes I could not even get her on plane. I ended up replacing the VST tank as it has a fuel pump in there that was only putiing out 30PSI. The boat is running a whole lot better, but once I get her on plane at 3000 RPM for about 5 minutes, she will start to bog down again. There is some mild surging, but not as bad as before. I have checked the exhaust for blockages and there are none. I have a new fuel seperator, distributor cap and rotor. Plugs are fairly new. Does this sound like a bad fuel injector? Any help would be appreciated by my wallet.

 

[tbirdvet]

Does not sound like an injector. Perhaps air flow sensor or still something related to fuel pressure.

 

[highball]

Change the spark plugs. I thought I had one motor running well and the other was doing roughly what you describe. Changed both engin spark plugs and it was day and night difference in both. I think the 7.4 mags are hard on plugs. I put in the regular plugs this time and none of the Platinums. ( the one with the tiny pins in the center)
Hope all goes well with you engin without too much $$$$$$

 

[sotaman]

Could cavitating or ventilating be the cause here? Props are 28 pitch? Can I see the effects of cavitating from the stern?
Tom