strange engine or prop (?) noise

Status
Not open for further replies.
B

butchrobbins

.
Jun 25, 2004
146
Catalina 310 Hilton Head
John said:
Darn! It seems there are no easy answers. I've never revved up the engine all the way, and I don't know what maximum rpm is for my Universal M35-b engine, but it doesn't seem to have any problems revving up. I've gotten it up to around 25-2700 rpm's with room to spare, so to speak. We bought the boat 2 years ago, and the pitch was checked at that time and was fine. To my knowledge, we haven't hit anything or done anything that would change that. I'll take your suggestions about a stethescope.
Click to expand
Is that under load or in neutral. My Univerasal 26hp is 3500 in neutral and 2500 under load.
 
Mike Holibar

Mike Holibar

.
Jun 26, 2007
106
Freedom F39 Lyttelton New Zealand
Butch, your engine sounds seriously overpropped. If you look at the performance curves for the engine, unless it has an automotive type governor, its 26hp rating will be developed at maximum rpm 35-3600 rpm. If you follw the curve to the 2500 rpm mark you will see the power developed is considerably less. So while your engine is nominally 26 hp, the way it is currently set up it is only (say) 15hp. As it only takes about this amount of power to drive a boat the size of yours at hull speed in fair conditions, this won't be much of a problem. But when you are in a tight spot and you need all 26 horses, you will find they are not available. Only 15 hp plus black smoke. Other problems, well canvassed in this forum, also arise with overpropped engines.
 
Maine Sail

Maine Sail

.
Feb 6, 1998
11,711
Canadian Sailcraft 36T Casco Bay, ME
butchrobbins said:
Is that under load or in neutral. My Univerasal 26hp is 3500 in neutral and 2500 under load.
Click to expand
Butch,

Quote from Universal Engines re: M-25 XP-B:

"Universal recommends a propeller that will allow the engine to turn 3000 RPM underway at full throttle"


If you are only hitting 2500 you are either way over pitched / propped or your prop or hull are seriously fouled. Another option is that your tach is off. That engine, with the governor, should only be able to hit 3200 even in neutral. Your engine develops a max HP of 26 at 3000 RPM and max torque (47 ft. pounds) at 2440 RPM which is right about cruise RPM..

Start with the tach and make sure it is calibrated properly then move on to other items such as fouled bottom or prop then onto the prop if everything else checks out....
 
B

butchrobbins

.
Jun 25, 2004
146
Catalina 310 Hilton Head
pretty sure its the tach

Maine Sail said:
Butch,

Quote from Universal Engines re: M-25 XP-B:

"Universal recommends a propeller that will allow the engine to turn 3000 RPM underway at full throttle"


If you are only hitting 2500 you are either way over pitched / propped or your prop or hull are seriously fouled. Another option is that your tach is off. That engine, with the governor, should only be able to hit 3200 even in neutral. Your engine develops a max HP of 26 at 3000 RPM and max torque (47 ft. pounds) at 2440 RPM which is right about cruise RPM..

Start with the tach and make sure it is calibrated properly then move on to other items such as fouled bottom or prop then onto the prop if everything else checks out....
Click to expand
I have had a couple of instances where it didn't even register-had to bang on it.
 
Status
Not open for further replies.

Top Bottom