Low power troubleshooting

[Ken Juul]

I've been fighting a low power situation for a couple seasons.  I think my prop may be slightly overpitched, but there is something else going on.  Injectors were new last season. Fuel tank has been cleaned, screen is off.  Did pick up a bad batch of fuel a couple years ago, after changing a couple racors the filters since have had their annual change before fouling.  I was beginning to think it was the injector pump, similiar to the problem Ron had a few years ago (see the Technotes).  I sent the local Kubota service folks a note, this is their response.

I FEEL YOU STILL HAVE A FUEL ISSUE WITH ENGINE. BLOW BACK WITH AIR FROM FUEL FILTER TO TANK TO REMOVE ANY ADDITIONAL BLOCKAGE THAT MAY RESTRICT FUEL FLOW. CHECK FUEL PUMP, BUT I DONT THINK YOU HAVE AN INJECTION PUMP PROBLEM. THIS IS VERY UNCOMMON ON A KUBOTA ENGINE. ALSO EVEN CHECK FUEL FILTER AGAIN FOR VARNISH OR DEBIS BECAUSE OF FUEL TANKS PREVIOUS CONDITION. HOPE THIS WILL BE HELPFUL.

From this my list of things to do when I recommission this spring has grown.
Blow out line from Racor to Tank, using dingy pump or compresser.
Electric fuel pump.  Check/clean filter, pump should put out 3-7 psi and pump at least 2 gph
Clean internal passages on Racor and engine mounted filter brackets, new filters.

Hopefully that will help, will report back.

[Ron Hill]

Ken : I'm not too sure if you told the Kubota people that you have an electric (lift) fuel pump in the fuel line. 
You can blow out all of the lines disconnecting them one by one.  However, you can also disconnect the output line from the Racor, and replace it with a length of fuel line and check the fuel flow into a clean container (by turning ON the key switch activating the lift pump).

I often thought that my "crazed" injection pump MAY have come from over "Biobor-ing" my fuel??  Then one time I found a strange substance in my fuel funnel screen.  When I threw that strange white substance overboard, it hit the water and started to spin around just like metallic sodium in water!?!

The only thing that I can say is that after checking/replacing all other fuel system components and the the engine still lacks power - it could be the injection pump.

You mentioned your prop.  If you have a Sailor style prop it would have to be pitched more that 11 inches to lug down the engine and not let it provide full power.  If you have a Michigan Wheel prop with wide blade causing a large blade cord surface area - then that's the problem.    A few thoughts

[Terry Forshier]

I experienced low power too. Sometimes it would hardly start just put put put then engage. Then I would only get 2200 to 2400 rpms in gerar. I cleaned prop, I put in new glow plugs, i checked and replaced injectors. Still low power. Many times it would constantly just slowly lose power. After many many hours of research I finally found the problem. The shut off cable was tightened too short on the lever that regulates fuel flow into the engine. When I lengthened the throw (the cable you pull to shut down). I found It had been tightened at least 1/2 inch too short causing the fuel line to be only partly open. Also when the cable would jiggle it would let even less fuel in and the motor would stall. When i changed this It was like a new engine. I now ave at least double the power. I know this may not be your problem but check it. I never thought of this and found it by accident.
Terry

[Ron Hill]

Terry : Great point !!  It's also something that I wouldn't have recommended that people check.

It's such a simple thing to check. I'd recommend all C34 owner regardless of engine ((M25/XP/35) check that cut-off cable. Just unscrew the screw that secures the cut-off cable, make sure the cockpit cut-off handle is down and the cut-off lever(on the engine) is all the way forward.  Then re tighten the securing screw.     

[SeaFever]

Does anyone have a photo of how the kill-cable is connected/fastened to the bracket? It should be connected at two places at least, I figure. The forward end is with a screw type fitting on the metal wire (mentioned by Ron in one of the posts above). I am interested to find out how the cable/sheath is fastened to the bracket. We can't over tighten that end as that could lead to a hard pull/push action. Appreciate your help.

[SeaFever]

Scratch that question. I checked out the Universal M25 as well as the D850 parts lists and got an idea of how the kill cable needs to be fixed.

I made an Aluminum bracket and fitted the kill-cable today. It works fine.

[prh77]

Regarding Ron's " crazed " injection pump, I have read that too much Biobor is tough on metal parts. Read the instructions, a little goes a long way.If you are adding "extra" to deal with an algae problem, either have the fuel polished or better yet, remove and clean the fuel tank. I had mine out in about half an hour. Very accessable-for a boat-.

[Ken Juul]

To amplify on the previous comment.  I was told at an engine seminar that unlike other fuel additives, Biobor isn't absorbed by the fuel.  If you add some with each tank top off the concentration increases to the point where it can damage the engine.  The instructors advice.  If your tank is almost empty, add biobor.  Every time you add fuel, add stabilizer/cetone additive.

[Tom Glennon]

Years ago I had a "low power" issue.

had the system checked out by an excellent diesel guru.... the fix was embarrisingly simple...
The nylon bleed screw on my racor filter wasn't tightened snug, and as a result I was sucking air which only allowed me about 1,000 rps at tops

[horsemel]

Take a look at the article on page 26 of the April 2010 issue of Sail Magazine.  The article is on propeller blade area.  Even if the pitch is ok, you might not be getting power you need because your blade loading may be too high or too low.  According to the article, under 6 psi is optimal for most sailboats. It would be interesting to know the formulas they use to calculate this information.
Mark Mueller

[Ron Hill]

Mark : You are saying the same thing that I've professed for years. 
The blade cord surface area is tooo great !! 
That can easily happen if your prop is NOT a Sailor style prop.   A thought

[Ken Juul]

My current prop is a Campbell Sailor.  It's design is unique.  Blade foils do the work not surface area.  It is 3 bladed, each blade is about 1.5" wide.  I have had it to the prop shop.  Using the computer diagnostics, I have confirmed that the prop is the size/pitch that the manufacturer says is right for my engine.  It has worked on a bunch of other C34/36s with the M25xp.  That is the reason for my frustration. 

Double checked the fuel system last weekend.  Pickup is clean, racor mount cleaned/new filter installed.  Pump screen clean, engine mounted filter changed.  Double checked that the cutoff valve was all the way open.  No change in loaded rpms before and after. 

Going to go back to the Michigan sailor 15x9 that came with the boat and see if there is any change.  I know the  9" is probably under pitched, but it is a place to start.

I know in the back of my head that it is something so simple I am missing it.  I'll let you know when I figure it out.

[Ron Hill]

Ken : FYI, the factory 3 blades Sailor Props were made in Australia (stamped on hub). 
All of the Michigan Wheel props that I've seen have a much larger cord surface area.  For what it's worth!