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Anyone ever have a 40/50/60hp EFI sound like this?

R

rotus623

Contributing Member
'07 60hp EFI

Had the boat on the trailer and was just letting the jet motor warm up and it started acting like this a minute or two after starting. Very strange. It has done it before, but always seems to be at idle just a few minutes after starting. This is on a cold morning (28 degrees) but I have had it happen warmer. Note that the engine runs strong, has great compression, and is not setting off any alarms. It runs real strong mid range and WOT and has never shown any other signs of issues that I know of. After running it will idle perfectly. I have never had this rough/strange idle when the motor is good and warm. It also sometimes takes 2-3 times to get it to start.

https://www.youtube.com/watch?v=L2sPIvY1bn8

And this is how it normally sounds:

https://www.youtube.com/watch?v=vMnzBAsZfjk
 
Ok fellas so I have an update.

I am nearly certain that this issue is a fuel issue.

I checked the resistance specs on the following sensors: engine coolant temperature/ECT, manifold air temp sensor/MAT, mass air pressure/MAP and crank position sensor/CPS. All tested out well. I even put the MAT and ECT sensors in 36 degree water and heated it up to 120 degrees slowly, and the specs matched up all the way through the temperature band.

So, after all of that, I started the motor last night (35 degrees out). I put a fuel pressure gauge on the VST fitting. The spec according to Mercury is 42-44psi. I got 60psi at idle, and it went up to 65psi at 1500-2000 rpms!!

I checked the resistance of the high pressure fuel pump and Mercury calls for 32-41 ohms. I got an OPEN circuit. 0 ohms, YIKES!! I checked it before and after I ran the motor for 30-45 minutes. Same-same........

I unfortunately could not duplicate the shuddering, because the motor would not falter. She was purring like a kitty!!
I know for a fact that this motor has seen plenty of ethanol fuels with no stabilizer. I also know that the fuel filters haven't been changed in quite some time.

My first plan of action is to tear down the VST, give it a good cleaning. Clean up/change the fuel lines, put on new fuel filters, install a brand new fuel pump and try it again. If I am still getting a very high PSI reading I will change out the fuel pressure regulator because it is right on top and very easy to get to.

Any suggestions guys? Would a shorted fuel pump run too high of fuel pressure? Or is there a blockage/issue in the fuel pressure regulator?
 
With an open circuit 0 ohms i would think the fuel pump would not work,check with another meter,check voltage going to fuel pump while she's running
 
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I know its pretty radical!! I need to rig up a test circuit so that I can test the voltage. Id rather not pierce the wires if I can avoid it.

I checked it with a better meter today and it had 2.0 ohms on it. This was on the 200 scale. If I went to the 20k scale it would read open.

Anyways, I checked my fuse harness, and the spare fuse was blown!

Its a clue!! And it has got me thinking. I wonder if the fuel pump went at one point in time and whoever fixed it put an aftermarket pump on it that had a higher pressure operating range on it. Going to have to tear into her and see what fuel pump is in there.
 
Success!! At least I feel that I can assume that for now.

Fuel filters were both dirty as all get out. The reason why the fuel pressure was building so high is because the inlet screen that feeds the fuel pressure regulator was almost COMPLETELY plugged!! I checked the leads directly on the fuel pump and they were again, 2 ohms. This thing was on its way out. I certainly would have been left out on the water by the looks of it. Check it out:



So I cleaned it!



And in general, the VST was just plain dirty. This is why we change our fuel filters and install racor water separators people!!





 
These items should be included in your annual maintenance to be on the safe side, all filters inspected and /or changed. Question #1 how is all that crud getting past the filters and water/ fuel separator? Fuel lines degrading from ethanol over the last 10 years??
 
johnnygjr said:
These items should be included in your annual maintenance to be on the safe side, all filters inspected and /or changed. Question #1 how is all that crud getting past the filters and water/ fuel separator? Fuel lines degrading from ethanol over the last 10 years??
Click to expand...

Great question.


I bought this engine second hand. The problem was so intermittent
that I think lots of guys would have let it be, but thats not how I
am. Gotta make sure all is well before I head out on the water.


My guess is that the fuel water separator has a break in the filter, or
yes, fuel line degradation (although it doesnt look like that to me.) It
almost looks like sand, actually. But it breaks down just like mineral
deposits. My guess is there was water in the fuel that carried minerals
and they settled into the VST.


Once I thoroughly clean a fuel system on a boat engine I vow never
to use ethanol fuel again, and I also use additives during storage.


Now I am wondering if I should clean, replace, or send off my injectors.........
 
Oh and it looks like there is a special tool to remove the injectors from the TFI manifold. Or can you just ease em out by hand?
 
water in an ethanol fuel system will leave behind mineral deposits upon degradation of that fuel over time "crystal like substances" As long as a cylinder is not running lean,I would not touch the injectors, They can be cleaned and flow tested for proper balance,but it looks like your filters did their job
 
Saw very similar crud in the filter of my Mercruiser 305. Took several cleanings, and flush of the tank, to eliminate it.

Jeff
 
Thanks guys.

Yea, vinegar broke it down real good, so I am certain it is mineral deposits from water in the fuel. Cleaned everything up real good. Waiting on parts to get it all back together. Ill let you know how it goes.

Luckily, High Flow Fuel sells aftermarket fuel pumps for $70. If I had to pay $500 for a new Merc fuel pump, Id probably leave this one in there until it croaked. Few reasons I am changing it: the resistance is off spec, I have heard a whine from the engine and I think its the fuel pump, running against a blocked output like that can't be good for longevity, and lastly, I dont want to have to get back into the VST anytime soon!!!

Cool way that I checked my fuel pressure regulator: I put my air gun to 60 psi and put it into the fuel input side of the regulator. When I let the air go through you could hear the valve squeal off of its seat, and as the pressure dropped down to around 40-45psi the seat closed and air didnt make it past the valve. No reason to spend $150 on a regulator that is working fine!
 
I cleaned the entire fuel system, and put all new fuel lines on everything. Brand new high pressure fuel pump also. I pulled the injectors just to make sure no sediment made it into the fuel manifold and injectors. Everything looked good and clean in there. This motor will only see E free now, as long as I own it.

Started her up and she ran great. Fuel pressure regulator read 44psi from key on, all the way up to 2000 rpms. That dirty screen was definitely the culprit. I didn't see any shuddering, and I will check back in to confirm after a few trips.

So at this point I'm going to call it good to go!! Thanks guys!!
 
For any fuel injected engine it wouldnt hurt to install a fuel filter water separator. It dont take alot of water to foul up the injectors.
 
Oh and I dont have a Racor, just a sierra water separator that you can get from walmart. Probably should invest in one, but knock on wood I have never had any issues with the ones I have been using. Just change em out once a year, and dont go more than 1-2 months without using the boats. (Note that this boat did NOT have one on it when I got it!)
 
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