Prop or Fuel

Status
Not open for further replies.
C

Charles6743

.
Jan 22, 2008
2
Hunter 20 Hudson
Have 1980 Hunter 33 with 2QM15 that turns the water black at 2000 RPM.
I took the mixing elbow off and it was not blocked. When I bought the boat I was told to run it at 1850 RPM. Did they know something was wrong when they sold it to me or did they try to save fuel by changing the prop.
The motor should turn 3000 RPM but it puts carbon out at 1950 to 2000 RPM and won't turn any faster.
It starts easy and runs smooth untill I get to 1950 RPM and has a speed of 5.2kt.
At 1850 RPM I am only getting about 7 HP. and not enough power in high winds & seas.
Any ideas on what to check next.
Thanks,
Charlie
 
C

ChuckThomas

.
Apr 24, 2006
194
Hunter 33_77-83 Mandeville LA
same boat. same engine. same issue. i have had my boat for about four years now. it is very happy at 1800 to 1900. it will push the boat about five knots. i have not had any problems going to windward even when hit one time in a thunderstorm in 50 knots wind.
 
Scott F. Murphy

Scott F. Murphy

.
Jul 10, 2005
21
Cherubini 33_77-83 New Orleans, LA
Two threads same subject!:)

Sounds like you could use the operators manual:

http://www.g-o.dk/Files/Billeder/PDF...bger/2QM15.pdf

Carbon will build up in the cylinder walls from running at low RPM. The manual suggested shut down procedure is to run the engine at idle for 5 minutes and then gun it to 2500 for a second. This blows out any excess gases and carbon. Since I started doing this, I've noticed a lot less carbon lately.
I have the original 2 bladed prop on my '79 33'. I seem to have 2 "sweet spots" for cruising, 2200 RPM's/5 mph and 3000 RPM's /6-7 mph. Between these speeds I get vibration resonance. From talking with other Cherubini 33' owners, seems to be normal.
 
N

n624ma

.
Jan 27, 2007
48
Hunter 33_77-83 Groton Ct
Low RPM

Warm up the engine an with it in neutral go to full throttle and see where to governor is set.

If the prop pitch ( or condition of the fouling on the bottom ) will not allow it to reach the rpm the throttle setting is calling for then the high pressure pump will push fuel to the injectors in an attempt to make more rpm's and the black smoke will pour out.

I have an 81 H-33 that I repowered with a 2GM20F and a VariProp and have had a great deal of fun getting the prop pitch right.

I originally had a 2GM in the boat and it came from the factory overpropped under no circumstances could the engine reach full rpm.

If you have a good prop shop around have them take out some of the pitch.
 
Paul F

Paul F

.
Jun 3, 2004
827
Hunter 1980 - 33 Bradenton
The prop has to much pitch for the small motor. I went from a two blade 14x12 (original prop) to a three blade 13x11 and picked up 500 rpms. My 2qm15 runs up to 2800 in idle and 2400 in forward. The black smoke is an indication that the engine is working to hard.
 
Paul F

Paul F

.
Jun 3, 2004
827
Hunter 1980 - 33 Bradenton
Yes knots increased by 1 to 1.5 Can now motor at 6-6.5 knots. A clean bottom and prop also helps a lot.
 
John Nantz

John Nantz

.
Jul 1, 1998
3,062
Hunter Legend 35 Poulsbo/Semiahmoo WA
Black smoke exhaust => over proped

I'd tend to agree with P Deitz that the cause is being over proped. Now, it may not be the only cause, but if the engine is over proped there will be black smoke exhaust and the transom will probably get grey from it too.

The Yanmars are not designed to be run at idle or slow, they like to be running at a good RPM. Same goes for siting at anchor and charging the batteries, it's not good to let it run at a slow speed.
 
Status
Not open for further replies.

Top Bottom