M25 RPM

[Richard Gresham]

On my 87' 30, under power, I can barely make 5 knots. worse if there's any chop. I can not get more than about 2000 rpm, according to the tach gauge. I have what I think is a standard Martec 12" or 13" folding prop. I've checked the throttle cable sleeve in insure that it was secure at each end, no problems. Next I disconnected the cable from the throttle body and losened the stop bolt to give it more room. But, the linkage won't advance any further. Am I missing something??  How do I check the accurracy of my RPM gage and what is the cruising and Max rpm's for this engine? Does anyone do better with their folding martec?Thanks!

 

[Gordon Torresen]

Catalina 30 with M25

Considering the M25 was also used for the C36, you have an abundance of power. If you lug down at 5 knots with a 12" or 13" prop, I would think something is wrong with the engine itself. You didn't say what pitch was on the prop, but with that diameter the prop should just about break loose with the 18 HP developed at 2000 RPM. The recommended prop for the application is a 13 X 12. Hand held tachs are available that can be used to check your tachometer. Most good mechanics have one. You should also confirm the accuracy of your speed measuring device. 6.5 knots should be easily attainable.

 

[Pat DiFelice]

RPM reply

Hi Richard, I have a Universal manual that gives me the RPM specs on your M-25. Max rpm (3000) Cruising range (2100/2600). Also regarding calibrating your tachometer, there is a battery powered timing light that measures your RPM's. You place a piece of reflective tape on your V-belt drive on front of your engine, then this timing light will read your RPM's, then at the back of your tach. there's a calibrating screw in which you would want to calibrate that to the reading on your timing light. Do this a different rpm intervals ei. 500,1000, 1500,2000. Becareful not to overrev the engine. At the moment I don't know where you would rent one of these timing lights.