Yanmar 2gm20FW

G

GreginVancouver

.
Dec 31, 2013
2
Hunter 31 Vancouver
HI All,

I'm trying diagnose a running issue with my 2GM20FW in my 84 hunter 31.

At idle, I can rev the engine to 3200 rpm. I'm seeing some a bit of blue smoke above 1900 rpm. looks like there some diesel/oil in the exhaust water too.

If the boat sits for a couple of days and I run it, I can get 2700 rpm under load. After running the motor for 5 or 6 hours, the max rev's I can get is 2200 rpm under load. the engine is burning a bit of oil (1/5 drop on the dipstick over 20+ hours of running under load). the boat is purring at 2100 rpm and I can make 5.4 knots on slack tide.

Any ideas?
 
M

mr c

.
Aug 4, 2010
77
hunter sailboat 31 northport
I had the same problem. My Exhaust elbow was clogged. I cleaned mine. I am now back up to 3200 rpms. I have the same boat and year but mine only has the 2gmf not the 2gm20f.
 
woodster

woodster

.
Sep 15, 2009
6,243
S2 9.2a Fairhope Al
GreginVancouver said:
HI All,

I'm trying diagnose a running issue with my 2GM20FW in my 84 hunter 31.

At idle, I can rev the engine to 3200 rpm. I'm seeing some a bit of blue smoke above 1900 rpm. looks like there some diesel/oil in the exhaust water too.

If the boat sits for a couple of days and I run it, I can get 2700 rpm under load. After running the motor for 5 or 6 hours, the max rev's I can get is 2200 rpm under load. the engine is burning a bit of oil (1/5 drop on the dipstick over 20+ hours of running under load). the boat is purring at 2100 rpm and I can make 5.4 knots on slack tide.

Any ideas?
Click to expand
how many hours is the yanny got on it and when is the last time you changed the oil and filter for starters ...oh and check the air intake for a blockage along with the oil breather (pcv) line in the valve cover to the air intake manifold
 
woodster

woodster

.
Sep 15, 2009
6,243
S2 9.2a Fairhope Al
mr c said:
I had the same problem. My Exhaust elbow was clogged. I cleaned mine. I am now back up to 3200 rpms. I have the same boat and year but mine only has the 2gmf not the 2gm20f.
Click to expand
good suggestion..... that was to be my next thing to check...
 
P

Pizzazz

.
Sep 11, 2015
147
Hunter 31 Marina del Rey
Make sure that your tach is reading correctly. I have a 1984 Hunter with the 2gmf. At full throttle, I get 2,800 rpm on the tach, 3,600 rpm if measured with a laser tachometer (you can get one for 14.99 from Amazon). At idle, it is 500 rpm on the tach, 900 rpm when measured externally. The actual rpm's are exactly per the service manual.

I typically motor around 2,200 rpm on the tach (which should imply around 3,000 actual) at around 5.5 knots. The max speed you can get on this boat with the stock engine is around 6.2 knots sustained, 6.5 for short periods of time. Under sail you can easily exceed this in the right conditions. However, I find it difficult to believe you can do 5.4 knots sustained at 2,100 real rpm. At this level, the engine is making around 8-9 horsepower, 1-2 is taken by the alternator, so you are left with 7 hp which is not enough to push 10,000 lb at 5.4 knots given our hulls.

Regards,
Pizzazz
 
You must log in or register to reply here.
Top Bottom