Lost 200 RPM, Where to Look?
I am having a small dilemma, since last season I have lost 100-200 RPM from WOT. Both engines. MPH is off a bit too. They run and sound fine. The only things I have done is change the oil and gear lube, clean the spark arrestors, and re-loom some of my throttle cables. I also had some very small leaks on the intake manifolds due to the bolts coming loose(went away after re-torque). Leaned out the idle circuit a bit too, was real rich. (this has been done since I noticed the problem) I checked the throttle cables, they are both on the stops with the sticks pegged, still really close in sync. Have run through multilple tanks of different gas so I dont think thats it. I havent changed plugs/wires since I got the boat last spring, maybe a possiblity? Or props messed up? Have accidentally run them in the sand a couple times while idling up to the local sand bar. Any other ideas or things I can look for? I am kind of stumped right now, especially since it is both engines.
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I would start looking at the props might have tweaked them in the sand
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How many times have you run since spring? You have to take in account air temp, humidity, load etc. Most engine builders will tell you that you hp in summer months. My boat is a few mph faster in low humidity, low temp days. I would also check the amount of ethanol in the fuel.
Also regarding the engines keep track of your compression. As they age and it drops so does hp. |
Originally Posted by Double Rigged
(Post 3461784)
How many times have you run since spring? You have to take in account air temp, humidity, load etc. Most engine builders will tell you that you hp in summer months. My boat is a few mph faster in low humidity, low temp days. I would also check the amount of ethanol in the fuel.
Also regarding the engines keep track of your compression. As they age and it drops so does hp. |
Originally Posted by firehawkcat
(Post 3461779)
I would start looking at the props might have tweaked them in the sand
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Originally Posted by AIR TIME
(Post 3461790)
yes thats a start, did you change fuel filters too, if not try that plus see if the carbs got gummed up. that could of happened over the winter. I lost 200 to 300 rpms with a bad fuel filter back in 1990 when gas was good.
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Originally Posted by firehawkcat
(Post 3461779)
I would start looking at the props might have tweaked them in the sand
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Don't forget the bottom of your boat. If you keep it in a slip, all it takes is one hot, humid week for the nasty green stuff to grow and it sticks unless you brush it off. That will easily cost you 1 or 2 mph.
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Originally Posted by E Colby
(Post 3461799)
Don't forget the bottom of your boat. If you keep it in a slip, all it takes is one hot, humid week for the nasty green stuff to grow and it sticks unless you brush it off. That will easily cost you 1 or 2 mph.
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Probably more due to the humidity than anything else.
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