69 Merc 1000 acts like 1/4 throttle at full throttle

[aeronutt29]

I did a re-ring job on this powerhead last year, cleaned/kitted the carbs this spring, rebuilt 1 of the 2 fuel pumps, installed an aftermarket ignition box/coil, did the link-n-sync, and properly adjusted the timing. The motor starts instantly, idles smoothly, has great low speed response, and sounds perfect. Compression on all 6 is 114 (+ or - 3). The problem happens when the trottle is advanced for some high-speed operation. Unfortunately, the aftermarket ignition system is incompatible with my tachometer so I can't report RPMs, but the sound and feel are as if I never advanced the throttle past 1/4. No hesitation, no sputtering, just good smooth-running low power. The carburetors DO open fully. Squeezing the primer bulb has no effect. <br /><br />One of my fishing buddies suggested that it might be sucking air or have one of the external air bleeder lines routed wrong. I've tried most of the suggestions listed on this BBS for similar problems, but it just doesn't respond.

 

[Yepblaze]

Re: 69 Merc 1000 acts like 1/4 throttle at full throttle

Might be sucking air. I suggest you make sure you have the ignition wireing correct cylinder for cylinder. Did you replace the check valves in those fuel pumps when you kitted them?

 

[aeronutt29]

Re: 69 Merc 1000 acts like 1/4 throttle at full throttle

I just double checked the plug wires. They are correct. The check valves were replaced in the one fuel pump. The other one went untouched due to lack of a second rebuild kit. I'm inclined to believe that the pump is not the problem since squeezing the primer has no effect.<br /><br />The one thing I haven't tried yet is squirting premix into the carbs while the engine is running. I'll try that this weekend.