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1973 Mercury 650 3cylinder

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bradmans

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Can anyone tell me what the no

Can anyone tell me what the normal WOT RPM is for this engine?
 
Your wide open throttle range

Your wide open throttle range is between 4800 - 5300... In a tank you should be looking for about 5200 - on the boat just over the 5000 (5050) is probably what you should be shooting for. More/less than that will require a prop change.
 
"Thanks Graham,

Now, I'

"Thanks Graham,

Now, I'm thinking I should try the other prop that came with the used boat. It's a little larger, but has less pitch. right now I'm running about 4500 (if I can trust the tach)"
 
"Yes, so that is a little low

"Yes, so that is a little low even for the range. Dropping the pitch by two should take you up near 4900 (which is better). You should keep in mind though too that the weather has a measured effect on the engine as well. Anytime the temp is over 70 and the humidity is above 30% your engine will start to drop off - so technically as the summer progresses you should down pitch your prop anyhow - but that's just the science
"
 
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