motor issues please help

[HBryant1978]

I bought a boat last year that has a 15hp Suzuki 4 stroke and I love the silent purr of the motor. The issue I am having with it is that it will not run a full speed. Once it gets the speed up and on plain the motor seems to hit a spot that appears to send it in limp mode and then if you back the throttle down about 1/4 of the way it runs perfectly fine and never skips a beat...just will not hit full throttle. Kinda like a rev limiter at full throttle. I have checked my full tank and fuel lines and even tried it with 2 other fuel tanks and different fuel lines. The fuel line bubble stays nice and firm but yet still does this ONLY at full throttle. I have asked a few people and they done seem to have a clue. I took my motor off my boat for the winter and when I put it back on the boat last week and hooked a water hose up to it, it fired right up with no problems but then noticed the water jet from the pump was not shooting in a stream but just pouring out but with no restrictions like maybe the rubber line could have came off or dry rotted. It seems to be 1 thing after another....

[Harper]

Do you know what RPMs you're getting when it starts to falter? Does it have a tach? Operating range is 5000-6000 RPM, and I'm guessing you don't have a tach hooked up to it. Not sure what the overspeed setting is on that motor, but you might well be hitting the rev limiter.

[Murray]

Where did you hook up the hose on your engine?

[HBryant1978]

I do not have a tach attached to my motor and 1 of my friends told me when motors are bought new they do not come with a prop on them and possibly had the wrong prop given to the original owner. And as far as the water hose hooked to it I was shown on the side of the motor there is a water hose port with a screw in cap and was told to unscrew the cap and put my hose there so that where i put it. I still wasnt sure if that is where the hose goes due to growing up my dad always had the clamp on attachment that he put down on the water intake on the foot.

[2014DF25ARS]

The hose port on side of the motor is not a connection to the cooling system. It is for flushing saltwater out of the engine. You still need the clamp-on "earmuffs" like your dad used, or run the motor in a deep bucket of water - which must be deep enough to cover the "cavitation plate" on the engine. I have a 3-cylinder engine (25HP), and when it hits the rev-limit, I believe the computer kills the spark to one of the three cylinders, which makes my engine run very rough. If yours is a 2-cylinder, perhaps the rev-limit leaves only one cylinder running, which could run fairly smooth (but weak). I don't know.

[HBryant1978]

Its not a smooth run. When it hist that spot its like ba..ba..ba..ba.. if you get the picture lol (bad description) like a car engine would do in park and you floor it and it hit its rev-limiter. And thank you very much for the info on the motor flush port cause I surly did not know that and thankful I have only used it only once and only for maybe 60 sec, but to be on the safe side I am goin to replace the impeller for the water pump just have have new rubber in the water.

[Moonlighter]

The simple things sometimes are worth checking - like spark plugs and plug leads.