We have a 440 Express Bridge with...

[A_Lot_More_Misc]

We have a 440 Express Bridge with Cat diesels, we typically cruise at about 1600 RPM, not in a hurry and we're towing a larger dinghy. On Friday evening, I thought I'd step it up a bit, but couldn't get the engines to go above 1600 at all, when I turned off the engine equalizer, which is controlled by the port throttle, the starboard engine worked just fine, but the port still wouldn't go above 1600. We've recently changed all of the fuel filters, I switched the inline filters over again, but that didn't help. When the engines are in neutral, both rev and run perfectly.

The boat is running flawlessly, at 1600 rpm, does anyone know where I might start looking for an issue?

Thanks, Wes

[Name44]

Could be something as simple as s fouled propeller, to something more significant. Start with a quick snorkel & take a look at the prop. Have a safety spotter with you. It the prop is clear, take air filter off & try spinning ( ENGINE OFF for this ) turbocharger. It should spin freely.

[SMT]

Check your electrical lines coming into the engine for corrosion in addition to your filters. I have a D450 with 3126 Cats and found the breaker had corrosion on the ground. Simple tighten and loosen with wd 40 and no problem.

[Bob_440_DA_w_Ca]

If your engine was only running up to 1600 due to a bad turbo or other major problem you would normally have heavy smoke or sooting or horrible noises. From what you say this is not the case so I would look for a problem with the throttle control. If cable controls something could have slipped. If electronic then some loss of calibration possibly.

[SeaMax]

Have your checked/replaced your racor fuel filters? I had a racor that had a vacuum leak and I had fits finding the problem. Look for any air bubbles in the sight glass but at cruise speed that is tough to do. One easy way to eliminate the racor is to switch the lines coming off the filters (starboard to port, port to starboard) and see if the problem moves to the other engine. If it does, you know where the problem is. After spending $45 on a racor rebuild kit (new o rings etc) to no avail, I ended up just replacing the entire racor housing - problem solved.

[A_Lot_More_Misc]

Thank you guys for your suggestions, I really appreciate it.

[PIKES]

I had a similar issue for me it was dirty Racors filters. I had gotten caught in bad storm and it stirred the bottom of the fuel tanks causing to dirty and clog the racors. Pull the racor filter and inspect. I also use 20 or 30 microns. If the fuel is purple in color it could be algae.

[Kmas100]

Are you getting any smoke from the engine at all? That could be a clue. What Cat engines are they? How old is the boat?

[A_Lot_More_Misc]

We get a small "puff" of smoke when we start each engine, apart from that, nothing at all. The strange thing is that the engine is running absolutely fine at 1600 rpms, just won't go any higher. We pulled the boat last weekend, I was really hoping to find something wrapped around the prop or shaft, but they both look fine as well. If it was the fuel, wouldn't both engines and the genny be acting up? I've run various configurations. Sorry for the stream of consciousness, I may need to scratch my head on this till spring.

[buddydog]

Check the connections at the end of the throttle cable. I had one strip on my Cummins engine. The engine just eased back to idle. The brass threads on end piece had stripped on the stainless cable threads.

[skalywag]

Check the air filters, most common cause for problems on Cat engines

[Jet_Rooster]

Does it labor at 1600? Or just goes right up and then won't go any further?

[A_Lot_More_Misc]

Jet Rooster, it runs perfectly at 1600, all the way up to 1600 as well, just won't do anything else.

Thanks Skalywag and Buddydog for your suggestions, the boat is out of the water and wrapped, but we will look at both of those ideas in the spring.

Thanks everyone for your help with this head scratcher, it's part of the value of being a Sea Ray owner for sure!

[Jet_Rooster]

Just out of curiously, does your throttle quadrant have a "DOCK" selection?

[A_Lot_More_Misc]

No it doesn't have a dock selection

[buddydog]

What is a throttle quadrant and what is a dock selection?

[Jet_Rooster]

DOCK is an RPM limiting selection on the Mercruiser throttle quadrant, to avoid over-revving the engine during close-in maneuvering.

[Jet_Rooster]

Mischief, this is a good site for reference:
https://www.sbmar.com/articles/understanding-low-power-troubleshooting/

[Jenny2]

I also have a 440 EB I had a similar problem but I have Volvos with electronic throttles not sure if the Cats are electronic or mechanical throttle. If they are electronic check the throttle control switches that are under the seat forward of the helm station. I checked mine with an ohmmeter and found it was getting bad. To check you can swap the wires and try it to see if the problem changes very easy to do at least on my boat. Just remember your throttles will be switched. Hope this helps

[Bob_440_DA_w_Ca]

If the port engine does not smoke when running at 1600 rpm with throttles all the way forward my guess is it is a throttle cable issue. Check to see if the throttle anchor point on the engine has slipped. You can also disconnect the throttle cable and have a brave soul manually run the throttle in the engine room and see if it goes above 1600 doing that to pinpoint if a cable issue or engine issue. I do not know much about the synchronizer but the problem could be in that unit possibly and harder to diagnose. Another option is to put both engines at full throttle not running and see if both engine throttle linkages move the same amount as they should do.

[runman]

This could be a problem with the auto sync. With a mechanical throttle there are parts in the sync system that get worn. Not expensive to fix. I had a similar problem

[SeaMax]

If the engines both run fine with the synchronizer disengaged, it is not in the synchronizer. If the engines both rev to hi rpms in neutral, it is not in the cables. Try changing the fuel lines downstream of the filters - switch port to starboard and starboard to port right at the filters. If the problem moves to the other engine, you know where to look. I had a racor filter that was somehow drawing in a little air - did a complete rebuild of the racor gaskets and that did not fix it. Frustrated, I replaced the entire racor - problem solved. I never did find the vacuum leak in the racor - strange but that proved to be the problem.