2500 max rpm at WOT??

skunkman

Active Member
May 27, 2014
452
Longboat Key
Boat Info
2014 330 DA sold
Current boat 2021 Formula 350CBR
Engines
Triple 350 Mercury Verado
My port engine was running fine until yesterday. At WOT the engine hits about 2500 rpm. The boat had a lot of people on board and could not get up on plane or go over 10 mph. No alarms or warnings and all looks fine on inspection. Any thoughts?

I didn't think to rev it in neutral
 
maybe a dead cylinder due to a bad spark plug, bad plug wire, or bad fuel injector.....assuming no recent changes in the prop.....

cliff
 
Check for fouled running gear (v-drive... outdrive?).

Check fuel pressure at rail.

Twin fuel tanks, right? Try running with your fuel cap off. Do you have a crossover? Try that.

Along the lines of what Cliff mentioned, physically check every plug wire (both ends) to make sure they are secure... not just a "looksie".

What did the stbd rev to during this time?

Don't worry about trying it in neutral - most likely it will rev all the way up, but that doesn't mean anything.
 
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Perhaps a silly question - but how many people is "a lot of people"? If you had 20 souls onboard with the BMI of a typical American....this may be a non-issue. She's a sport cruiser...not a freighter :)
 
There were 11 people on board - about 1400 lbs total. The starboard engine went up to 3800 rpms.
 
The starboard engine went up to 3800 rpms.
OK, that helps. The reason I asked about that RPM was the same reason some were asking about the number of people. I would "expect" that if the boat was overloaded, then both engines would be running roughly the same RPM. But that's a big difference.
 
I would check for fouled running gear first.
 
How do you do that
Hold your breath. :) You're looking for rope, or something, wrapped around the prop shaft/propeller/drive. Sometimes a "fouling" can actually cause the RPM's to increase due to ventilation - but it's a good first step to checking this out and it's a freebie.
 
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If you have I/O’s you can lift the port drive and make sure the prop is okay.
If you have inboards or V drives you’ll have to go for a swim.

Or hire a diver...They are inexpensive and valuable. Have them scrape your bottom while they are there. I'd guess less than $100.
 
Check the throttle cable for proper adjustment.
 
The boat is kept on a lift and the bottom is clean. The props look good. I am taking the boat in to a marina for other repairs and hppefully thry can chase this down and find something simple. I will check the plugs and wires first.
 
Took the boat out again this weekend with just the wife and dog. Ran great up to about 3600 rpms then the port engine lagged slightly. I did get a misfire warning on the port engine before I started it. The next day I got a misfire warning on both engines but they both ran great. I did not run at wot.
 
Sounds like a tuneup is in order after verifying that you can get your boat to run the way it did before you put 11 people on it
 
Many of the questions asked above still apply, so check into those. Will you be doing any of this work yourself?
 
So when you and your wife went out were your throttle levelers normal getting your motors sync. These were all the signs I had when dealing with a miss.I went through all the checks did a tune up still no solutions to the problem. Now my symptoms were not as noticeable as yours but I never loaded her up with a bunch of people but I'm sure it would have been the same.After a tune up and checking your fuel rail pressure if this doesn't fix the problem I would check you motors cylinder compression. Turns out I had a intake valve leak.
 
It is ready for routine service so I will take it in to have a pro look at it when the wife is willing to part with the boat!!! In the mean time I may get a code reader to see if I can figure out what cylinder is misfiring.
 

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