KL Won’t Get Over 1500rpm under load?

[tim.whipple]

I have a 1949 Chris Craft Deluxe Runabout with its original KL, intake flipped and Rochester Model C single barrel downdraft, carb, water pump, fuel pump and Pertronix all new rebuilds by Van Ness, new acme correct size/pitch prop (according to hull card: 12.5x13), starts/idles/cocktail cruises perfectly… but won’t go over 1500rpm under load. Anybody have any ideas? Thanks! In advance!
PS - got boat from a buddy, they’ve had it for decades… same problem, they just used it for cocktail cruises, so no big deal for them, I’d like to get this thing moving and planing.

[Badger85]

Start with the carburetor. Incorrect float level (too low) can limit the amount of fuel. Also, if it has been rebuilt, the needle valve may not be the original style requiring a different float setting than Zenith specs call for or improper needle valve gasket.

I had a needle valve in my carburetor loosen up and as it came unscrewed (happened slowly over time) the max engine RPM's slowly decreased. Twin carbs on my engine so it was hard to pin down.

[tim.whipple]

Thanks Badger! Will check that today and reply. Further note, played with the timing a bit (advance under load) and am getting 2100rpm now, and planing. When adjusting timing, should I be using screw, or distributor collar? Been a while since I got to play with this stuff.

[Badger85]

Can use the screw or bolt. I was told the flat plate at the base of the carb with the slot is a leftover vestige from old car days when a linkage attached to the distributor and the driver could manually advance or retard the timing under way.

Could also try tapping the carb with a rubber mallet. Not uncommon for the needle valve to hang up after a winter layup. Usually presents as an engine that will start and idle but not accelerate without coughing and wheezing (starved for fuel). It's good that these old boats are not unlike their owners;)

Careful not to add too much advance.