[Klaas Kos]

Hello all,

I have a SX18 from 2001 with a mercruise V6 4.3 190 hp. I have installed a 19P x 14 1/8 4 blade stainless steel propellor.

I only get 4000 RPM with full throttle and max speed is 42 mph. When the engine is in neutral i get easy 5000 RPM and maybe more with full throttle.

Does anyone has a sugggestion what the problem can be that i cannot reach the normal 4800 RPM and max speed from at least 45 mph.

With the original prop. 3 blade alu. 23P x 14 5/8 i had the same problem.

The engine runs very smooth and has enough torque.

[mikeyt]

Here's a list of possible causes...most of these you can eliminate pretty quickly.

Engine Won't Reach Operating RPM. Check

Fuel condition. Type and Octane possibly old fuel
Propeller pitch or diameter, damaged blades
Restricted fuel pickup tube or anti siphon valve Fuel System Test
Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
Marine growth on hull and outdrive
Wrong gear ratio in outdrive
Restricted carburetor air intake (clogged flame arrestor)
Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
Poor cylinder compression Compression Test
Carburetor defective, or wrong type.
Fuel pump pressure and vacuum
Boat overloaded, improperly loaded, or improperly trimmed.
Engine Overheating
Engine timing and ignition system operation
Remote control cables and linkage for proper travel to open throttle plates fully.