Diaganostic Help

SeaRenity

Member
Mar 31, 2008
200
chesapeake bay / Back river
Boat Info
320 Sundancer 2005
Engines
350 Mag hor.
As you can see by my signature I have 350 Mag horizons, which the starboard engine for the last year has shown some changes. I noticed it takes more throttle (than port) to get to the desired RPM ( usually run 3800 or so) this engine also seems o burn more fuel ( port 12.6 gph vs 13.5 for engine in question.
I've read here that possible fuel injectors could be the problem. Need help with determining if it is injector problem -- how do I know and is there something I can do.
I always run Star-tron with my gas and I am forced to use E10. Any help???
Thanks
Rich
 
Have you tried something that will clean the injectors a little more? Maybe sea foam? Also, is that the difference for just the engines or you also run a generator from that tank.
 
I'd check to make sure it's not something more obvious before diving in on internal engine components. Are your throttle cables still 100% free and adjusted correctly? They can creep/stretch over time (at least mine have). If your boat is out of the water you may also want to make sure something hasn't happened to your running gear. Arrestors both clean? Trans oil fresh, both sides?
 
Thanks for the responses, I ruled out throttle cable because along with increased throttle I have noticed higher than usual fuel usage. I do not have a generator so, this is not the culprit and it would not effect gph while running. Boat is on the hard and running gear appears fine. Tranny fluid has been replaced recently and new plugs, rotor, cap and wires have been installed on starboard engine
 
You can run a fuel pressure gauge, but it only tells you what is feeding the injectors - it won't tell you what the injectors are actually doing. Injectors can be cleaned for about $20 each and there are worse things to do - worst case, it's good PM for the future. I do think it would be a good idea to run the fuel pressure gauge, though - just to help narrow things down as you're in the era of the CF paint problems.
 
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SeaRenity, Had same issue. Powering up you have more throttle than the motor gives you rpms. My mechanic diagnosed mine by ruling out the fuel pumps, took out and bench tested flow, filter - replaced, plugs - replaced. After all this he sprayed fluid straight down the air intake and the motor ran smoother. This bypasses the injectors. Removed injectors and sent away. After re install, sea trialed boat with him. max rpms before was 3200, now max is 4450. And what a huge difference in power getting up on plane. I did the other motor myself with the assistance of a friend for about 1 third the cost of the marina. I sent my injectors out to:
They clean them to original specs. Check out their web site. Only takes about a week.
Best thing I did in regards to performance and power. At WOT, I used to get up to about 35 - 36 mph, after the cleaning I can run 44 with good sea conditions and a light load.
Unless you are familiar with doing this, enlist the assistance of someone who is.
 
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actually this supplements the injectors with extra fuel....the fact that the engine started running smoother when fuel was shot into the air intake told the mechanic the injectors were not supplying enough fuel.....most likely because they were dirty and partially clogged.....

cliff
 
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Judging by your year (2005) I assume you have Cool Fuel 3.

If you haven't had them replaced, and you're concerned about the internal paint issue, you can put a fuel pressure gauge on the motor(s) to possibly diagnose and issue.

If you see noticeably higher fuel pressure, that is a symptom of paint fouling the fuel system.

43 psi is the spec for my 2007, it was over 55psi according to the work order when it was diagnosed as needing the new CF3 module a few years ago.
 
Thanks for all the help. I do have CF3 and I have had relay issue and somewhat burnt connectors on the relay which might tell me I have a high draw from increased fuel pressure?? Does the interior paint on the CF3 clog the injectors or just contaminate the fuel filters??
 
The filters generally aren't affected, as they are placed before the area where the paint delaminates. The paint moves down the line and affects the fuel pressure regulator and the injectors.

FYI, there are 2 fuel pressure regulators on the CF3 engines. One is on the fuel rail on top of the intake manifold, this one isn't used, its essentially a Dummy. The "real" fuel pressure regulator is mounted on the CF3 module. You'll see a small vacuum hose attached to it. If you remove this one, you may be able to see paint chips and debris if in fact you have a "CF3 paint issue"
 
You should have a Merc shop look at it - if it is due to the paint issues, there's a possibility that Merc will cover the repair. It seems to be on a case-by-case basis and somewhat determined by how the Merc shop presents it to Merc.
 
SeaRenity, Had same issue. Powering up you have more throttle than the motor gives you rpms. My mechanic diagnosed mine by ruling out the fuel pumps, took out and bench tested flow, filter - replaced, plugs - replaced. After all this he sprayed fluid straight down the air intake and the motor ran smoother. This bypasses the injectors. Removed injectors and sent away. After re install, sea trialed boat with him. max rpms before was 3200, now max is 4450. And what a huge difference in power getting up on plane. I did the other motor myself with the assistance of a friend for about 1 third the cost of the marina. I sent my injectors out to:
They clean them to original specs. Check out their web site. Only takes about a week.
Best thing I did in regards to performance and power. At WOT, I used to get up to about 35 - 36 mph, after the cleaning I can run 44 with good sea conditions and a light load.
Unless you are familiar with doing this, enlist the assistance of someone who is.

Hi, first your boat is beautiful. Have a question - How long and how big a job is it to remove fuel injectors...
 
If you suspect a clogged injector or you confirmed that there is indeed paint debris in the fuel system, it may be difficult to pinpoint which injectors are affected, they may all have debris in them. A good mechanic with the proper computer diagnostic tools could be a help, but his cost could be more than the money saved by cleaning say, 4 injectors vs. 8 if that was the case. (Looks like you are attempting to do this yourself)

If you suspect a clogged injector or you confirmed that there is indeed paint debris in the fuel system, then i would recommend having them all cleaned or replaced. You will also need to flush the fuel line from the CF3 module up to and including the injector rails.
 
Clean them all. It only costs about $20 each and, at the very least, it's good PM. Have you talked to a Merc shop as I suggested above?
 

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