Engine Not Producing Full Power

[senorquill]

Good evening everyone,

I had my local marina mechanics change out my water flange (for way to much money) which requires taking the gear case assembling off. Now that is all back together the engine does not power up fully. When idling it sounds just fine, but when I push the throttle up it only reaches like 1900-2000 RPM at Max throttle. It sort of sounds muffled. I changed out both fuel filters, nothing changed. I took off the air intake and inspected it, just fine. The throttle assembly on the engine is going to full throttle position. The engine ran for 2+ hours the day prior to them touching and it was running great.

What could this be?

Link to You Tube showing the problem: https://youtu.be/OAQbiWK48GU

No, they won't help me now. They just keep asking me if it was like that before, so I gave up asking them.

Anything would help.

Thanks,

MQ

1987 C34
Universal M25XP (1700hrs)

[mark_53]

Just a guess but is possibly running on 2 cylinders? Faulty injector?

[Jim Hardesty]

Just a couple of guesses from me.  Look at the fuel lines for damage.  Crushed? Crimped?   Check that the fuel pump is running.  Double check the throttle throw.
Hope that helps,
Jim

[senorquill]

Just a guess but is possibly running on 2 cylinders? Faulty injector?

Is there anyway to determine if only 2 cylinders are firing? Or is that something a mechanic can just sort of listen for? Same for injectors, how to know one is faulty?

Thanks

[senorquill]

Just a couple of guesses from me.  Look at the fuel lines for damage.  Crushed? Crimped?   Check that the fuel pump is running.  Double check the throttle throw.
Hope that helps,
Jim

I'll trace the fuel lines this morning and attempt to re-bleed. I think the fuel pump is working since when I changed the primary fuel pump it filled it back up with fuel fairly fast.

Thanks.

[scgunner]

MQ,

Before I did any of the above I'd check the throttle linkage, is the throttle opening up all the way? One thing I've learned over the years when I don't know what's causing the problem I try the easy things first.

[senorquill]

MQ,

Before I did any of the above I'd check the throttle linkage, is the throttle opening up all the way? One thing I've learned over the years when I don't know what's causing the problem I try the easy things first.

It's going all the way to the stopping nut. Both from the cockpit control or manually.

[senorquill]

MQ,

Before I did any of the above I'd check the throttle linkage, is the throttle opening up all the way? One thing I've learned over the years when I don't know what's causing the problem I try the easy things first.

What is your idle RPMs? Maybe the entire throttle handle got hit and pushed off center or something. I'm at 1000RPM idle. I just did a Seafoam treatment and have been motoring for 30 minutes. Can only get 1900 RPMs. Engine sounds good.

[mark_53]

Just a guess but is possibly running on 2 cylinders? Faulty injector?

Is there anyway to determine if only 2 cylinders are firing? Or is that something a mechanic can just sort of listen for? Same for injectors, how to know one is faulty?

Thanks

Lack of power is a symptom.  I would look at the injectors and see if something may have become disconnected.

[senorquill]

Video of the issue.

https://youtu.be/OAQbiWK48GU

[Ron Hill]

MQ : Have you taken a laser tack and checked it against the installed engine tach?  Then you know the real engine RPM!!

A thought

[senorquill]

MQ : Have you taken a laser tack and checked it against the installed engine tach?  Then you know the real engine RPM!!

A thought

The tach worked fine before this. The engine is just not getting enough power. Motoring at full throttle was only getting me 4.4knots today with no wind or current in the bay. Usually if I have the throttle 3/4 it would produce 2400 RPM and get me 6.2 knots. So tach or no tach, it's not producing power. It also just sounds weak, smooth, but weak.

I think I'll start removing all the fuel lines and make sure nothing is obstructing them. Next step I guess, would be to remove the Fuel Injectors and take them to the diesel mechanics in town for a service.

I'll to find the correct factor PSI for those things.

Thanks,

Ryan

[KWKloeber]

s/v Dude

This is a good example of what I have said on my soapbox so many times.  Don't eff with more than one thing at a time.  Is it the mechanic's problem with the gear cover removal/replacement or a fuel problem?
Who knows now. 

Folks learn the hard way but then others don't pay attention so they themselves will get into a pickle.

For the fuel -- DO NOT (YBYC) start removing/testing engine parts (injectors, etc.) before you or someone diagnoses the cause. 

It's MOST likely NOT something that you or the mechanic did not touch.  Components like injectors and pumps don't magically go bad when other work is done on an engine or fuel system. 
If she ran fine BEFORE, then why think that something else went bad while the boat was sitting idle?

FIRST, try running the engine with the fuel bleed valve half-open or full open.  Some owners say that their engines need to have that open.  Why? I have no clue why that would make a difference but I don't question their experience on their engine.

MOST likely if it's a fuel problem there's a vacuum leak -- which can a bugger to locate.  DO NOT (YBYC) start haphazardly replacing hoses and gaskets.  You may never discover the root cause(s.)
First -confirm whether there is a vac leak.

I have posted many times about the (IMO stoopid) way the XP has the fuel bleed set up.  It is IMPOSSIBLE to tell if you have bled the fuel and all air is out.  A convenient but near-useless setup.  (IMO) the setup should be changed as I did on my engine.
 
Remove the fuel bleed hose at the bleed knob and plug it off.
Put another hose on the bleed knob and bleed into a glass jar so that you can see the fuel condition. 
Foamy? (vac leak)
Is it clear? (inconclusive)
Strong fuel flow (pump ok)
Weak flow? (bad lift pump or plugged pump screen, or blockage in the line somewhere)

If that doesn't reveal an obvious problem, close the tank valve.  Use a cheap brake line bleeding hand pump from Harbor Freight and apply a vacuum onto the fuel line to the Injector Pump (remove it at the IP and put the hand pump there so that you are testing the entire fuel train -- from the tank to just before the IP.)
The vacuum should hold.
If not it indicates a vacuum leak.
Now to locate it.

Backpressure the fuel line from the same place -- the hose you tool off the IP. 
Or if it's easier, use the hose between the tank and Primary Filter and plug off the hose that you that took off the IP. 
Apply JUST A LITTLE air pressure, 4-5 psi, and look for a leak by spraying or brushing on a dilute dish soap mixture to locate the leak (air bubbles.)

On the mechanics' work - Unlikely but possible that something got screwed up w/the governor or speed control (you wouldn't necessarily see this just by looking at the linkages/adjustments.
Did the mechanic run the engine after doing the work (to ensure that there were no coolant leaks)? 
At what RPM?
Did she get up to temp? 
If not, get a different good diesel mechanic.

Ask the mechanic to check the speed control adjusting bolt.  That could have gotten out of adjustment.
If he doesn't know what that is, find another good diesel mechanic.  I would NOT eff with adjusting anything there (YBYC) unless you know what you are doing.

If one cyl is not producing, cracking the fuel line nut sequentially at each injector will reveal if an injector is bad. 
There will be a noticeable drop in RPM when you starve the good injectors of fuel.  The RPM won't change on the bad injector.

You might also need to bleed the fuel line at the Secondary Filter - the engine manual (TechWiki site) shows where that bleed is.  Or bleed the line to each injector (cracking the nut at each injector.)  Those two are a last resort, and are NOT typically necessary.

My guess (and Occam's Razor) says start by ruling out a fuel/vacuum leak --  but yah never know.

Good luck hunting/diagnosing and let us know 'bout each step you try.

[Dave DeAre]

I had the exact symptom with my MK2 M35. It was the fuel pump. Replaced and has been good for 6 years. Not the same engine, but same symptom. Be sure the pump wires were not disconnected; I think Mk1 M25 may still run with a defective pump.
May not apply but worked for me. Good luck!

[Jim Hardesty]

I agree with Ken.  It's not good practice to just start changing out parts.  More often than not it's a waste of time and money, sometimes compounds the problems.
If your tank is less than full, maybe topping off will help your problem, then you can suspect the fuel pump.  Our boats will run with a bad fuel pump and a full tank.  If you haven't done so check the fuel shut off at the tank, make sure that it's full on.
Jim