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Tohatsu 8 5 pitch too low for a sailboat

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"Title says most of it.

Boa


"Title says most of it.

Boat is a Catalina 25 that checks in at 4500lb before gear. Motor pushes it at 6.2 knots at 1/3 throttle. I don't expect much more - maybe 0.3 or so. Motor seems to run slow, but I haven't figured out how to measure the RPM.

Standard pitch is 7.5. Would going to 5 be too low?

Would this increase my fuel consumption?

Would I hurt the motor by going everywhere at low RPM and 1/3 throttle?

Thanks.

Matt in Detroit"
 
"Correct propping can only be

"Correct propping can only be done by trial and error, but....

Would going to 5 be too low? Seems a little extreme based on what the 7.5 is doing. I would S U G G E S T dropping to a 6.5 pitch as incremental changes are always a safer choice.

Would this increase my fuel consumption? You bet. Increase in RPM's will increase full usage.

Would I hurt the motor by going everywhere at low RPM and 1/3 throttle? No, but your ability to turn would increase with a lower pitch prop."
 
"I got a tinytach and mounted

"I got a tinytach and mounted it. With the stock prop (7.5) I am turning 4200 at 1/4 throttle and 4400 at 3/4 throttle. Not to 10 hours yet, so I don't know full throttle.

From another post, I saw that each inch is approximately 200rpm. Is that a good estimate to go by?

Should the engine be running at 5-6k rpm?

Thanks."
 
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