DF140 Very little speed or RPM's under load no more than 4000 But fine on muffs

[rhumbaclave]

I have a 2008 df140 I have been slowly but surely trouble shooting. Right now the problem is in the water it will not get over 4000 rpm's mostly stays around 3000. I put it on muffs and it goes up to 6000 no problems in gear. Neutral is okay but it does a weird sneeze backfiring sound once in a while.

I have a new Low and high pressure pump
VST has been emptied, removed and cleaned plus new pin and float.
New fuel lines
New spark plugs


The prop that is on the boat is a SOLAS 9431-135-15

Any suggestions

[jHydroman]

I would try running the engine on a portable fuel tank, if no improvement I would check compression next and change spark plugs at the same time is they haven't been changed lately.

Jim

[rhumbaclave]

Compression was low like 100psi. I know this is a dumb question but what would that mean?

[rhumbaclave]

Oops duplicate post, but each cylinder was within 5 psi and the engine only has 150 hours. I
cannot image a ring is out?

[jHydroman]

You will not develop rated HP with compression that low, per service manual compression should be 182-242 PSI. Make sure you are using the proper procedure when checking compression. The low compression could be caused by rings not sealing, valves not seating, damaged cylinder walls, bad head gasket.

Jim

[artdf175]

add to Jim's post check valve clearances

[briscoe]

What about the water separator? Does the fuel in the low pressure filter look clear? This sounds fuel related to me. Start on the simple things first. Pull the exhaust silencer and then pull the rail to the injectors. Pull each injector. I had some pluggage from crap in my tank and you could visually see they were plugged. There is a way to check if they are spraying a good pattern into a mason jar.
This is a fuel issue.... just sayin.

[artdf175]

this observation was already mentioned but worth saying again Do Not run these engines more than 3000 rpm in neutral --- and at 3,000 only briefly --

now the other observation is the prop
if it is not set up with the correct size prop for your boat you won't get the desired results..

best thing to do is talk to a dealer
maybe if you mention the boat you are using this on someone else with knowledge of prop sizes can give some advice
Art

[catacom225]

Is this a new boat which came with these issues or have you owned it for a while?. So has this problem just started or has it been progressively getting worse over time. Did it run or rev ok with that Solas before, did you just get a tank of bad fuel , what did the old plugs look like!, So much information needs to put forward so the many experts on this forum can diagnose instead of guess.
So some history and a little more info would help get a little closer to solving these issues

[jHydroman]

I wouldn't spend much time or money looking for remedies for the loss of RPM's until you determine that the compression is actually "like 100" or correct the problem causing the low compression. You can not expect the engine to perform as designed with 100 PSI of compression.

Jim

[Suzdf140]

Hi I have a similar problem with my 2004 Df140 runs fine fine out of water no problem revs up and hits limiter in gear when out of water feels like it is running good but put boat back in water same problem again runs around 3000rpm won’t get over 4000rpm.
i have checked fuel , changed fuel water separator filter
changed low pressure fuel filter
cleans low pressure fuel pump
cleaned Vst Tank
cleaned all fuel lines
installed new spark plugs
connected to diagnostics no fault codes showing
Done injector actuator test on all 4 injectors test ok
But done misfire test on all four cylinders and found cylinder 1 & 4 to make no difference to engine running.
with more troubleshooting disconnected ign coil pack for cylinder 1&4 and the engine still ran the same and made no difference to running. Disconnected ign coil pack to 2&4 engine stops.
This is as far as I have got at the minute. It’s hard to believe the engine would run fine out of water on only 2 cylinders but it does. Maybe check if you have the same problem by disconnecting the ign coil pack electrical connector on cylinder 1&4 when engine is running and see if it makes a difference to the running of the engine and if it does reconnect and try again with the ign coil pack for 2&3 when engine running

Paul

[rhumbaclave]

UPDATE:

I got sick of borrowing compression testing kits from Auto Parts stores and bout my own. This proved to be worth it. All 4 cylinders tested in the high 180's so that is not the issue. I guess that is good news. I scoured the internet and found others with similar issues and they said injectors were the problem. So I replaced all four injectors to no avail. Still have the issue.

As far as prop, I believe the prop is sized fine according to local dealers and online tools.

I will check if it is running two cylinders. I am about to surrender and look at a new ECU or at least a used one?

We put it in the lake last night and we can putt along pretty steady but only at 2000rpm's if I give it more throttle it bogs down like it is starving for fuel...But all fuel pumps are new.

HERE IS THE BOAT STORY GO AHEAD AND JUDGE

This is a new to me first boat. In March my wife said we should get a boat this summer! I got super excited and found what I thought was a great deal and in 1 week was driving home our new Landau 25foot tritoon. We did a test drive on the lake and it had some trouble starting but the owner said it just needed gas and when we fill dit up it ran fine. It was pretty choppy that day so I couldn't really open it up but it ran okay 6k rpms easy. The hours read as 150 hours on the 10year old engine! I thought I was getting a still for our market especially.

Next problem was after I gave him the money he said the trailer wasn't titled(which in Colorado it has to be) So it took an entire month for that to happen before we took it on the lake.

On our first lake trip it started up okay but but idled rough ( I was on the lake and googled enough to think it was the IAC) It stalled in a cove and I got nervous. HERE IS WHERE I SCREWED UP I THINK. I happen to have a jump starter on the boat and I thought maybe it wasn't just getting enough amps from the batter. So I hooked it up. All of the sudden we smelt burnt wire and the engine stopped cranking.

After a tow back home I replaced the destroyed starter and the IAC. I then smelt fuel in the oil so I replaced the low pressure pump. That helped the fuel leak but didn't help the rest. Once a week I have been taking the boat our diagnosing something new and growing more and more frustrated.

I took it to a boat mechanic ( the one who right before I bought it replaced the high pressure pump) And he noticed the engine revved up when spraying some carb cleaner so he thought it was the manifold gasket...did that. Nope.

In the mean time my kids are having fun putting around the lake but I am loosing my mind. Our local Suzuki authorized dealer called it "winter work". Since we are not sure what is wrong with it.

DID I FRY THE ECU? With my jumping it?

Please talk me off the ledge.

[Moonlighter]

Get an experienced Suzuki mechanic to bet it hooked up to the Suzuki Diagnostic System computer.

I would be very surprised if they couldnt get it diagnosed fairly quickly.

[rhumbaclave]

Get an experienced Suzuki mechanic to bet it hooked up to the Suzuki Diagnostic System computer.

I would be very surprised if they couldnt get it diagnosed fairly quickly.

The local boat shop wants 270 just to hook it to a computer and it would take 2 weeks. I ordered this. Hopefully I can do it myself. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[rhumbaclave]

PROBLEM SOLVED. I fired it up on muffs last Saturday and noticed a new fuel leak. It was leaking on the VST gasket. I had an extra gasket so I went in... Found out yes the gasket was worn but that wasn't the main problem. The Bushing for the high speed fuel pump was not seated properly and fuel was leaking into that upper area from there. The bushing was actually damaged. The biggest miracle is the local boat shop actually had one in stock. I have had the boat in the water twice since then and IT RUNS GREAT! Thanks to all who helped me. This is a great site.