270 loss of power

[tomofficial2]

I have twin 1984 270's, after running 45 minutes or so at 2300 rpm my port engine had a 3 to 400 rpm loss of power. It took significent throttle to regain the 2300 rpm crusing speed. I recently replaced all of the fuel filters. I have replaced the points with Pertronix electronic ingition system. Have new plugs and coil. The coil resister is old. I think it is a fuel problem but not sure where to start. Thanks for your help!!

 

[makomark]

single tank or dual tanks?

I'd verify the spark is still consistent and then debug the fuel system.

Carbs serviced recently? Fuel pumps age? anti-syphon valve clogged? Dirt in the tank coagulating at the screen at the bottom of the pickup tube?

 

[tomofficial2]

Dual tanks, don't know the age of the pump. how do I verify spark at high speeds?

 

[fastjeff]

It's unlikely that this is a spark problem or the motor would loose a lot more power.

Try this: When the motor sags, manually add some choke (work the linkage by hand) and see if it helps. If it does, there's yopur answer: fuel starvation. You'll need to study the carb--arrestor temporarily off--to see where and how to move the choke linkage, to put some choke on.

Jeff

 

[tomofficial2]

Thanks!

 

[makomark]

I usually use a timing light to verify spark occurs.

Jeff's "choke manuever" will only work if sufficient fuel is on the float bowl. if it doesn't work, time to get the fuel pressure gauge out.