Engine synchronization on hp 500's
 

My boat was perfect when I put it up last year. This year the port engine runs 2-300 rpm more at the same throttle position. what in the hell could have changed?? I'm gonna check the timing this week but it has me puzzled. Any ideas would be appreciated...

Fogging oil is a killer on plugs. Check starboard for a fouled plug, or a gummed up carb jet , etc

I didn't fog it but I will go through the carbs...

could be fuel system related to ignition related. I would look at your distrib cap and rotor first then move on to other ignition components like coil, spark plug wires and so on - checking spark plugs and condition along with examining them for lean or rich conditions. Possible carb overhaul, Also comp test and fuel pressure test would nt hurt either.

300rpm drop is usually a good sign of being down a cylinder

You mentioned 300 more rpm at same position however is it at full throttle? Ck cables and throttle position vs plates on ea also.

I hear you that's why I mentioned examine the spark plugs and a comp testing wouldn't hurt either. You know really a forgotten test that not many do anymore is a vacuum gauge testing and power balancing testing. I would a do vacuum testing, they can determine a lot.

Weak or a problem with the valve springs too.

What is power balancing testing?

The jist is we use a digital rpm gauge, and ground out spark at each cylinder one by one and look for rpm drop - if no rpm drop that is your problem cylinder. We use 3 inch vacuum hose lead that connected to the distrib terminals and spark leads and ground each by a grounded test lite.

I just did all the heads and springs last spring. I bought cap and rotors so that will be first....