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Engine cuts out at acceleration above 1100 rpm.

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boatyard13

Member
Help is always appreciated.Have a 93 Mercruiser 4.3 Alpha One Thunderbolt. Idles beautifully at 650-700 rpm. First thought was bad gas. Pumped fuel tank dry of very cloudy/watery gas and had carb rebuilt. Still cuts out on earmuffs and on water. Timing light showed Timing so retarded, it wasn't even on Timing bar. Advanced Timing at 8 before TDC and rpm jumped to 1000+- on low ram scale of Hawk diagnostic tuneup analyzer. Attempting to lower idle screw, brings idle screw out of contact.
 
See if the interrupter switch is being activated when advancing throttle lever. It should not. If it is then that would point to shift cable adjustment as a POSSIBLE problem.

As far as timing, What ignition do you have? TBIV or TB V? You should have a TBIV.

Double check you had timing light on #1 spark plug wire close to spark plug......sounds like you had timing light on wrong plug.

("""Timing at 8 before TDC and rpm jumped to 1000+- on low ram scale of Hawk diagnostic tuneup analyzer. Attempting to lower idle screw, brings idle screw out of contact.""")
 
boatyard13 said:
Help is always appreciated.Have a 93 Mercruiser 4.3 Alpha One Thunderbolt. Idles beautifully at 650-700 rpm. First thought was bad gas. Pumped fuel tank dry of very cloudy/watery gas and had carb rebuilt. Still cuts out on earmuffs and on water. Timing light showed Timing so retarded, it wasn't even on Timing bar. Advanced Timing at 8 before TDC and rpm jumped to 1000+- on low ram scale of Hawk diagnostic tuneup analyzer. Attempting to lower idle screw, brings idle screw out of contact.
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Make sure your throttle cable is adjusted at tge carb to light push the throttle blades closed against the adjustment screw
 
Attempting to lower idle screw, brings idle screw out of contact.
Click to expand...

The wrong carb base gasket will keep you from setting idle mixture. The correct gasket is thick about 3/32". I like to use a vacuum gauge to set it. There is a plug in the manifold near front of carb you can remove and install a nipple for vacuum checks.
 
Thanks. Carb was rebuilt by County Carburetor. The best around here since 1971. Turned out timing was waaaaay off. So reset and now performing well. Next working on installing new bilge blower.
 
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