Why am I losing power?

[63 Nova]

Hey guys I am new to the board and I need help.<br />89 Sea Ray 4.3 Mercruiser. It cranks fine and runs perfect until it warms completely up. Then it starts to lose power at WOT. If I back it down it will run but is still sluggish. We have changed the fuel/water seperator and rebuiolt the carb thinking it was starving for fuel...it didn't help. Surely with 50,000 members someone else has had this problem too. My next step is coil and ignition module does this sound like the right direction?

 

[WillyBWright]

Re: Why am I losing power?

Only if you're losing spark. Connect a timing light and see if the flashes go away when you're experiencing problems. If it still flashes consistently, your problem is probably not in the ignition system. Check your drive's gearlube. Your problem could even be there.

 

[63 Nova]

Re: Why am I losing power?

Thanks, Willy B I haven't thought about that.

 

[SS MAYFLOAT]

Re: Why am I losing power?

Check your fuel pump pressure, and double check your float level. Either one can cause a lean condition which is bad on the ole engine.

 

[achris]

Re: Why am I losing power?

Have you tried the ground wire on the dissy yet?

 

[jeremyp111]

Re: Why am I losing power?

I just went through a similar problem. If you connect the timing light and you confirm spark when this occurs then you obviously have a fuel issue. My problem ended up being the anti-siphon valve on the fuel tank. It's a little check valve that is most likely threaded into a fitting on the tank and has a barbed end for the fuel line going to the engine. There's a little ball and spring inside that would get stuck and not let enough fuel flow at WOT or near WOT. Replaced with a new one and all is well.

 

[63 Nova]

Re: Why am I losing power?

Thanks guys I'm going to test spark this weekend and mabey check another coil I have just laying around. I will then try the anti siphon valve check because I have been reading a good bit about that.

 

[Skipster1]

Re: Why am I losing power?

Loss of power - as you described - is sometimes caused by a filter in the fuel line getting plugged up with crud from the tank. As you run the engine the crud piles up, plugging the filter. When you shut the engine off the pressure in the fuel lines kicks back, unplugging the filter.<br />Check all filters and replace those you suspect.