1 GM Low Revs
Moderator: Jim Walsh
-
Dick Kobayashi
- Posts: 596
- Joined: Apr 2nd, '05, 16:31
- Location: Former owner of 3 CDs, most recently Susan B, a 25D
1 GM Low Revs
For some years now, my 1 GM will not rev to m ore than 2700 rpm under load. It will rev to the specified 3300 rpm without a load. Boat seems to move well but this is a constant and irritating fact. Any suggestions as to cause?
Dick K
CD 25D Susan B #104
Mattapoisett, MA
Fleet Captain - Northeast Fleet 2014/2015
Tempus Fugit. And not only that, it goes by fast. (Ron Vacarro 1945 - 1971)
CD 25D Susan B #104
Mattapoisett, MA
Fleet Captain - Northeast Fleet 2014/2015
Tempus Fugit. And not only that, it goes by fast. (Ron Vacarro 1945 - 1971)
Re: 1 GM Low Revs
Hi Dick,
Have you examined the exhaust mixing elbow to see if carbon build up is restricting the exhaust? Otherwise someone here who is more knowledgeable will chip in. I am assuming your filters have been changed not too long ago.
Have you examined the exhaust mixing elbow to see if carbon build up is restricting the exhaust? Otherwise someone here who is more knowledgeable will chip in. I am assuming your filters have been changed not too long ago.
Steve
Wondering why we are all not out sailing now?
Wondering why we are all not out sailing now?
Re: 1 GM Low Revs
I guess the first thing to look it at is the prop. You could ask other 25D owners what pitch and diameter they're running.
If it's different from yours, perhaps you could buy (on trial) a new prop or have your present one re-pitched less aggressively. - Jean
If it's different from yours, perhaps you could buy (on trial) a new prop or have your present one re-pitched less aggressively. - Jean
Jean - 1983 CD 33 "Grace" moored in
Padanaram Harbor
Massachusetts
Padanaram Harbor
Massachusetts
Re: 1 GM Low Revs
Hi Dick,
My MD7A never goes above 2700 under load but will go to 3K plus with no load and in calm seas that will push her to 6.2 or 6.3 knots. Were you ever able to get it over 2700 under load? Will be interested to see what others see with their boats and motors.
Keith
My MD7A never goes above 2700 under load but will go to 3K plus with no load and in calm seas that will push her to 6.2 or 6.3 knots. Were you ever able to get it over 2700 under load? Will be interested to see what others see with their boats and motors.
Keith
Re: 1 GM Low Revs
Unfortunately, there are a lot of things that can cause this. The advice to check the exhaust elbow is good. The original
Yanmar elbow rusts away pretty quickly. Better to replace with a SS one - cheaper than the factory too. If you're
determined to solve this, you could get a mechanic to do a compression test. This will help rule out worn rings, bad
valves, etc. Other factors : restricted air flow, weak fuel pump - possibly even plugged up vent for the fuel tank.
Good luck - Jean
Yanmar elbow rusts away pretty quickly. Better to replace with a SS one - cheaper than the factory too. If you're
determined to solve this, you could get a mechanic to do a compression test. This will help rule out worn rings, bad
valves, etc. Other factors : restricted air flow, weak fuel pump - possibly even plugged up vent for the fuel tank.
Good luck - Jean
Jean - 1983 CD 33 "Grace" moored in
Padanaram Harbor
Massachusetts
Padanaram Harbor
Massachusetts
Re: 1 GM Low Revs
May be time to have the injector serviced also...
-michael & Toni CDSOA #789
s/v KAYLA CD28 #318
2012 FLSTC Heritage Classic
Niceville FL
+30° 30' 24.60", -86° 26' 32.10"
"Just because it worked, doesn't mean it works." -me
No shirt + No shorts = No problem!
s/v KAYLA CD28 #318
2012 FLSTC Heritage Classic
Niceville FL
+30° 30' 24.60", -86° 26' 32.10"
"Just because it worked, doesn't mean it works." -me
No shirt + No shorts = No problem!
-
Bob Lascelles
- Posts: 198
- Joined: Jan 19th, '13, 18:08
- Location: S/V Vindolanda CD25D #111 1983
Re: 1 GM Low Revs
Hi Dick
My 25D also has a 1GM. It came to me with a Michigan Sailer 12” dia. 12 pitch two blade prop. I usually power at about 2700 rpm. But working against wind or current at full throttle she will put out about 3100 +/- rpm. It sounds very busy but seems to do that without much problem. I had some air leaks in the fuel lines when I first bought her and that really affected starting and rpm, I also had the injector worked on.
Good luck
Bob
My 25D also has a 1GM. It came to me with a Michigan Sailer 12” dia. 12 pitch two blade prop. I usually power at about 2700 rpm. But working against wind or current at full throttle she will put out about 3100 +/- rpm. It sounds very busy but seems to do that without much problem. I had some air leaks in the fuel lines when I first bought her and that really affected starting and rpm, I also had the injector worked on.
Good luck
Bob
Bob Lascelles
CD25D Vindolanda #111
York, ME
CD25D Vindolanda #111
York, ME