I have a Kholer Command CH25s model 1996 in my mud boat that ran great for years and just died one day just after launching into water. I replaced one coil and got it running again. Shut it down after a minute and decided to change the other coil and both plugs. Set gap on coils with a playing card. Started right up, ildes good, and idles up high RPMs no problem. Launched boat in water to run and after getting on wave about two minutes later started feeling a knocking in the engine and loosing power. slowed down tried reverse,, engine speeds up fine no knocking. Idle up out of gear no knocking. WTF.. Clutch / shaft problem ?? felt like i was hitting small logs with my prop. Changed cutless bearing, and replaced clutch with a loaner.. Shaft or clutch doesn't vibrate or knock in reverse. Never hit anything with prop. Definatly not the clutch or shaft.. Back to engine.. took old coils to repair shop,, they said the old coils got hot and melted because there was black puddy looking stuff on the connectors. They recommended I try changing the Speed Advance Module as this controls the coil signal. Replaced the speed advance module and engine still doing the same thing. Losing power after warming up under a load but idles up fine and smooth. what else could be the problem, already $350 bucks in. Seems like bad gas or carberator problem would effect the engine when its cold as well and it would run crappy even idleing with no load. very frustrated as problem cannot be duplicated at the repair shop so i need to fix it myself. Please HELP !!!

 

Are you running ethanol or non-ethanol fuel? And, if ethanol, are you taking proper precautions and using an ethanol treatment, like Sta-Bil Marine Formula, at each and EVERY fillup? The engine running fine at idle does not necesarily mean you have a carburetor that is functioning well...there are several circuits within the carburetor. Do you have the tools to perform a combustion chamber leak-down test on each cylinder? That would be my first step in making a diagnosis. My gut feel, based on your explanation, is you have a parasitic problem, not an engine problem. But, again, a leak-down test will help you figure out your issue.

 

Thanks for comment Puey61 !! I use ethanol fuel and never have used staybill or fuel treatments. many friends of mine have mudboats with these engines, kholer, subaru, vangaurd..noone has mentioned to me about using staybill or treatment. I'll put staybill in and see if it makes a difference. also I ordered a diaphram for the accelerator pump which is leaking fuel around the boot a fair bit. I can get my hands on compression test tools. my boss has two race cars.. he should have these tools. If compression test is good then would you suggest that it may be something simple as cleaning the carberator and using good fuel ?

 

Adding ethanol treatment at this point will be moot. It will not revive bad fuel, it will only prevent. Also, while a compression test is fine, it does not tell you much information if it fails this test. But, if no leak-down tester is available, such will do.