Raised engines 2 holes - some difference

[Lunchmoney]

I raised the engines 2 holes over the weekend and ran her yesterday evening. The AV plate is still under water at speed trimmed up, but not by much. I've only got one more notch available to raise them so I'm going to leave em where they are for now.
The port engine will now hit 6200 rpms trimmed up but the starboard will only hit about 5100. Think I'm going to swap props between the motors and see if the issue stays on the starboard side or if it moves to port with the prop. It did seem to steer a bit easier and my top speed increased 2+mph. I have another idea to try. My battery cables are original, 14 years old and have lived the salt life. I can bend them and hear some cracking internally. I put the volt meter on the starter and got the same voltage as the battery. I ohmed through them and had almost no resistance so i don't think that's causing my issue but being that they are original and I can hear the strands breaking when I bend the wire, it's time. I had a 90hp Yamaha years ago act strangely and it turned out to be the power cables.

[Nayna32]

My experience is about the same as yours, with the exception of a RPM or MPH increase. Only one hole left to go up, and the anti-ventilation plate is almost skimming the water.

Are your motors counter rotating?

[Lunchmoney]

They are not. I have a 25' Seacat and was told by the seller that due to the sponsons being so far apart, and thus the engines, counter rotating wasn't needed. Since I bought this thing 9 months ago, I'm learning a lot of what he told me was BS so...

[Moonlighter]

Good work, i think you are taking a systematic approach and this will help nail the issue down eventually. Lifting motors to the optimum height for any hull will make a real difference to hull attitude, stance, overall feel, responsiveness to trim etc.

I have a mate with a 6m cat twin DF115A's and the boat builder and Suzuki both said it was a no brainer to get counter rotating engines, its just so standard there is no real reason not to go that way.

Still, seriously weird to be 1000rpm apart on revs between engines. The props would have to be markedly different to make such a difference.

I take it that they sound noticeably different at WOT?? Its not just an errant tacho??

[Lunchmoney]

Bad tachometer crossed my mind but I can hear and feel the difference in the two. They respond to throttle advancement identically up to about 4500 rpms and then starboard side just won't respond like port during the last couple of inches of travel. I'll keep stabbing at it, hopefully I will get it pinpointed. They are both running strong, no misses or anything abnormal throughout the rpm range. Idle fine. Easy to start. Not using or making oil. New power cables are due in Friday. I'll get them on over the weekend and try her again.