Full throttle RPM

Status
Not open for further replies.
G

gulfsailorp323

.
Jul 31, 2005
35
- - Pensacola, FL
I took my 1994 C270 out yesterday for the first time to see how the diesel was going to perform. It ran smooth enough, but I found it did not take much throttle to get to 2800 RPM. My understanding is that this is the maximum cruising RPM for the Perkins M20. I could have gone over 3000RPM easily, which concerns me. Shouldn't the full throttle position be somewhat equal to maximum RPM under a load? It seems to me that I am either undersized relative to the prop, or something else is going on. I know I most likely have a dirty bottom, and probably the prop is all fouled with barnacles as well. I didn't get much speed at 2800. I will be hauling the boat in a couple weeks, and would like some thoughts on what others experience with the same boat and engine. What prop size are you using?
 
C

Calif. Ted

.
Jun 8, 2004
2,959
Catalina 320 Dana Point
Stock prop is 13 X10 , should get boat speed

over 6 knots at 2800 RPM in smooth water. These tachs are electrically triggered by the alternator, when shutting down you must wait for the tach needle to zero after pulling the fuel stop, then turn the key off. If you turn the key off the needle stops where it is and makes it even more inaccurate. If the last time you shut down the needle stopped at 600 RPM it would read 600 high next time you start. That's a 2 blade prop, BTW.
 
G

gulfsailorp323

.
Jul 31, 2005
35
- - Pensacola, FL
Thanks for the prop size

Thanks Ted. I will check the prop size once I haul the boat. The tip on the Tach is helpful as well.
 
K

Ken

barnacles

It doesn't take much growth to foul a prop. If the prop can't take a good "bite" out of the water it will just spin at engine speed, like reving the engine in neutral. Also relates to the slower speed you noticed.
 
J

Jack

Ted

Ted, Thanks for the info, I pick-up more bits of info from this web site. I never checked to see if the tac was at zero before turning the key off before, but I will now. again, thanks, Jack
 
C

Calif. Ted

.
Jun 8, 2004
2,959
Catalina 320 Dana Point
The nature of tachs on most diesels is such

that they are not real accurate. Hull speed for our boats is 6.5 Kts. and in perfect conditions engine will move the boat that fast at about 80% WOT or ~2800 RPM. Most times in open ocean, if motoring, 5 to 5.5 Kts. seems a comfortable speed for the boat, engine & me and fuel consumption is so low as to be laughable. Things like currents and wind can so greatly effect performance that you can trick yourself into thinking something is wrong till you get a feel for the boat under power in different conditions. The 270 is a really excellent boat, I'm sure you guys will really like it. I'm going out today for a couple days even tho the weather is a little "unsettled" this week, & cold.
 
Status
Not open for further replies.
Top Bottom