H49 YANMAR 4JH4 HTE problems

[miguelgdelrey]

Hello. I am the owner of a Hunter 49 2009.
The other day the RPMs on my Yanmar 4JH4 110 hp could not go over 1600
After motor sailing for about 3 hours with oil pressure and coolant temp ok.
I lower the RPM to about 1000 to anchor and the engine died.
I changed the fuel lines to the aux tank that has a different pick up and racor filter, but nothing happened.
That night we used the generator for aprox 8 hrs with fuel from main tank with no problem (so fuel is ok) next day I checked the line that goes into the tank and was clean, I checked the 2 micron element on the racor which was clean but I put a new one, I also changed the fuel element on the engine itself, it was also kind of clean with only about 60hrs, I bleed all the air from the tank to the engine with the engine pump. The engine started at first strike and stayed at idle for 10 minutes with no problem. I ask for someone to accelerate in neutral while I checked the engine and it would not go over 1600 again. I checked the cable and the lever was making the complete movement. I also move the lever on the engine directly with my hand and the same happened, only 1600.
Going back to the marina I started the engine to furl the sails in and after about 25 minutes, when I lowered the RPM to about 1000 the engine died again. At Idle the engine would not start, but it would with 1/4 of the throttle up.
The temperature was always normal, the oil pressure also normal, no black smoke, no white smoke. The only different thing I noticed is that before when at idle the engine would run around 800 RPM now it was between 600 and 700.
Is there anything else I should be looking for?
Need help here.

 

[Don S/V ILLusion]

The fuel pump, clogged injector(s), sprung governor...

 

[Bill Roosa]

Since it happened "all of a sudden" and with out any accompanying loud noise you probably have a mechanically intact engine. So compression should not be an issue. That leaves fuel and intake/exhaust flows to check.
If you start robbing the engine of air you get smoke so the air circuit is probably ok also.
Which leaves only fuel. Your supply seems to be ok so, as Don noted, everything from filter to injector (and the return lines if so equipped) need a closer look.
Since the problem is low power and you did not indicate a rough running engine but did mention idle problems your injectors either all went south at the same time or they are fine (probably the latter)
That leaves only the fuel pump. Servicing these is not for the faint of heart. Lots of close fitting parts that HATE dirt, they really HATE it A LOT. If you go the service it yourself route just act like you are operating on a person

 

[artboas]

Think I know how to fix this

Since it happened "all of a sudden" and with out any accompanying loud noise you probably have a mechanically intact engine. So compression should not be an issue. That leaves fuel and intake/exhaust flows to check.
If you start robbing the engine of air you get smoke so the air circuit is probably ok also.
Which leaves only fuel. Your supply seems to be ok so, as Don noted, everything from filter to injector (and the return lines if so equipped) need a closer look.
Since the problem is low power and you did not indicate a rough running engine but did mention idle problems your injectors either all went south at the same time or they are fine (probably the latter)
That leaves only the fuel pump. Servicing these is not for the faint of heart. Lots of close fitting parts that HATE dirt, they really HATE it A LOT. If you go the service it yourself route just act like you are operating on a person

You might consider installing a 12v electric fuel pump at the tank. This same thing happened to another 49 and that cured it.
The pumps are very inexpensive, (<$100), and it's worth a try

 

[artboas]

Pump mfg.

You might consider installing a 12v electric fuel pump at the tank. This same thing happened to another 49 and that cured it.
The pumps are very inexpensive, (<$100), and it's worth a try

The pumps are mfg. by Facet

 

[Stu Jackson]

And you can get them at auto stores.

Maine Sail also wrote an article on his own website pbase about servicing these older pumps, with pictures.

 

[Brad Hoff]

As a thought, have you checked your mixing elbow? I have a problem with low power when mine is clogged.

 

[miguelgdelrey]

thanks!!!

I will take note.

 

[Saillife]

Why a 2 micron racor filter? That's what is on the engine. My understanding is that you should have a 10 micron. The idea being that it catches all the big stuff & the 2 on the engine deals with the rest. By having both filters be 2 micron the second one (on the engine) is never being used.

 

[miguelgdelrey]

It is the racor brown element. Is it 10 or 2 microns?
I really don't remember.

 

[Benny17441]

Check the condition of your oil, a ruptured diagraprahm on the lift pump can reduce the volume of pumped fuel while allowing fuel to leak into the cranckacase diluting the oil. The tell tale signs are; an increase in the oil level and a marked smell of diesel fuel. Before you do anything remove the filter element from the Racor, close it up and start the engine. If it runs fine then it suggests the 2 micron filter you are using is to restrictive. Like Saillife indicates a 10 micron is more suited as a primary filter.

 

[miguelgdelrey]

Hello to all.
Finally it was the engine diesel pump.
At the lab they told me that a small metal part of the pump got lose and brake hell inside the pump $$$$$ they rebuild it and after 2 days of disassembling and reassembling (why is it always so difficult to remove anything from your engine?) we have the power again!!!

Thanks again

Miguel