Lost RPMs

[Kirbyvv]

I got the X-18 back together by July 4th weekend (after a deck off gas tank replacement project). I had the carb rebuilt and engine tuned by my local mechanic. She was running better than I've seen, 60 mph at about 4900 rpm. Its a stock 260 hp SBC. Slowly over the last couple weeks the performance has dropped off. I'm only getting about 4400 rpms now. Any ideas where I should start looking for the lost rpms?
I could take it back to my mechanic, but it isn't very convenient and they are very busy.

[mrfixxall]

I got the X-18 back together by July 4th weekend (after a deck off gas tank replacement project). I had the carb rebuilt and engine tuned by my local mechanic. She was running better than I've seen, 60 mph at about 4900 rpm. Its a stock 260 hp SBC. Slowly over the last couple weeks the performance has dropped off. I'm only getting about 4400 rpms now. Any ideas where I should start looking for the lost rpms?
I could take it back to my mechanic, but it isn't very convenient and they are very busy.

its the hot weather,mine will loose rpm's when its hot out..try a evening cruise and see if you get your rpm's back..

[Tidbart]

hot weather and ethanol-based fuel will drop the rpms.

Bob

[gcarter]

Since you had it tuned, did the mechanic tighten the distributer?

[mrfixxall]

you may also want to check the screen on the pick up tube, sometimes they get slag particles on the screen from welding the tank together..premimum fuel helps too..

[Kirbyvv]

thanks, I'll check the pick-up and distributor. It's definately been hot, but I never had it drop off like this before.

[LKSD]

Hot & Humid does rob power. Also depending on how you have the boat loaded with persons or gear it can slow you as well.. Other than that I would recommend that you at least do a quick recheck of you mechanicals to be safe.. Jamie / Lakeside.

[Kirbyvv]

It must have been the heat and humidity. Ran right up to 4900 on Saturday with low humidity and 78 degrees.