YANMAR 4JH3TE Slow throttle response when hot

Jul 23, 2009
497
Beneteau 31 Oceanis Grand Lake, Oklahoma
I once had a riding mower that would intermittently suffer from fuel starvation. It seemed to do it on the hottest days, seemed heat related. After much rebuilding, cleaning, replacing & cursing I finally found a fuel line that had failed internally. It looked fine and would flow fuel most of the time but not always. Never had any more trouble after I replaced that line.
 
Jun 15, 2012
628
Hunter 50 AC St. Petersburg
Normal temperature on my Hunter 50 is 165 degrees. I think 180 degrees is too hot. Over the last weekend towing a large dingy swamped with water and the outboard in the down position (outboard off) I was running 170-173 degrees.
 
Aug 9, 2019
13
Hunter 460 Maryland
Fuel tank vent is wide open. It's right next to the fuel fill and I can hear the fuel gurgling while I fill the tank...I've also shot some of the fuel foam out the vent before, so I know it's open.
 
Jul 23, 2009
497
Beneteau 31 Oceanis Grand Lake, Oklahoma
After reading through the links above it really sounds like you have a problem with the governor inside the injector pump.
 
Aug 9, 2019
13
Hunter 460 Maryland
Normal temperature on my Hunter 50 is 165 degrees. I think 180 degrees is too hot. Over the last weekend towing a large dingy swamped with water and the outboard in the down position (outboard off) I was running 170-173 degrees.
What engine does your Hunter 50 have in it? I haven't ruled out a hot engine. I still need to do a flush of the engine coolant and punch all of the cooling bundles - check for flow etc.
 
Jun 15, 2012
628
Hunter 50 AC St. Petersburg
If you are 110 percent sure that fuel is not the problem, I think it boils down to engine temperature (too hot) or air leak when hot or the turbo. I think easiest thing to do is check engine temp with an infrared non contact sensor to check accuracy of gauge. If sensor concurs with gauge I would remove thermostat and see if temp decreases.
 
Aug 9, 2019
13
Hunter 460 Maryland
I have the same exact engine and water cooled gear box oil as well. I haven't gotten to the cleaning of the cooling system. She's been out on the hard for the last 3 months and bottom paint was the priority. The engine definitely runs better with cooler water, so I'm still in the camp of a cooling issue. Found the temp gauge is completely inaccurate.
 

NYSail

.
Jan 6, 2006
2,742
Beneteau 423 Mt. Sinai, NY
Question..... how do you know the mixing elbow is not blocked? If it’s based solely on water flow you may want to open up and inspect the exhaust side. My last engine had full water flow however the exhaust side of the elbow was 80% blocked / coked up and caused somewhat similar conditions. Just a thought..... start simple and move from there.

good luck
Greg
 

NYSail

.
Jan 6, 2006
2,742
Beneteau 423 Mt. Sinai, NY
Question..... how do you know the mixing elbow is not blocked? If it’s based solely on water flow you may want to open up and inspect the exhaust side. My last engine had full water flow however the exhaust side of the elbow was 80% blocked and caused somewhat similar conditions. Just a thought..... start simple and move from there.

good luck
Greg
 

Pshad

.
Mar 6, 2020
5
Hunter 43 Seattle
is it possible your compression release is partially open?
 
Last edited:
Mar 6, 2008
694
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
Since you have confirmed that it is heat related by opening up the engine cover, I wonder if your alternator is the problem. It's bearings my be causing extra load on the engine . How is the belt. Is there much black dust near the belt?
Haro