Significant Drop Off in Top Speed

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swe67

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Mar 31, 2014
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Fluid Motion Model
C-24 C
Non-Fluid Motion Model
Cutwater 28
We picked up our new 2014 Cutwater at the beginning of this season.......For the first 100 to 150 gallons of fuel, I cruised at 20 knots around 3000 RPM without a problem after getting up on plane at 3400 RPM and 25 knots and backing off....Using 12 gph, a near 2 nmpg at 19 to 20 knots....This was with two adults and one child and 70 to 50 gallons of fuel on board....I would putt along at 1320 RPMs and get 6 to 6.5 knots depending on the seas...

After tanking up last weekend, I couldn't achieve any speed or RPM above 3000 even at full throttle. I assumed it must be the weight of the fuel as the seas were calm.....I was using 12 gph and only hitting 14.7 to 15 knots.....Today, we started with only 75 gallons and still couldn't get above 3000 RPM and get up on plane as boat topped out at 15 to 16 knots. Conditions were fair, so it wasn't the sea.....I can understand the slower speeds to some extent, but the inability to go beyond 3000ish RPM is somewhat disconcerting.

Any help?
 
Sounds like a prop problem to me??
Chester
 
Do you keep the boat in the water? You may have a build up on the bottom and on your running gear.m
 
A thumbs up for Mike's suggestion. Have it lifted and inspect. Ask the marina mechanic to look with you as he likely has an experienced eye for propellers.
One thing I would do first though, is get the engine running and use the decoupler button to advance the throttle with the transmission remaining in neutral. Go full throttle (let it warm up for a couple of minutes first) and see at what rpm the governor limits the engine. It should immediately go to full rated rpm (from your manual) with no load and stay there.
 
I leave it in the water.....Long Island Sound......I was thinking of having a mid-season hull cleaning lift out anyway....I will ask them to inspect the running gear while it is out.....Novice question, but where is the decoupler button located?
 
It is on the throttle/shifter. Either a button or lever so you can throttle up without it shifting into gear
On my 2009 tug it is a button right below the throttle arm at the pivot point. With the engine idling you depress the button with your left hand and advance the throttle with your right

If you have a two lever set up for throttle and shift on your Cutwater, pass go and collect two hundred
 
Sounds to me like you could have some bad fuel that is plugging your filter or intake screen. Did you put marine diesel fuel treatment in with the fuel? Diesel grows crud if not treated and that plugs filters and you get fuel starvation.

Robert
 
Check your fuel filters it sounds to me like a clogged filter. If it is not a clogged filter check the prop are you getting any type of vibration from your running gear??

Ronnie Gonzales
Cutwater Customer Service
Ronniegonzales@cutwaterboats.com
425-220-3932
 
Had the boat lifted out and cleaned......Prop was good and nothing impeding shaft.........I will swap out the fuel filter this week and add fuel treatment....
 
Have you tried it since cleaning yet? This is describing something similar to me and my 2014 R-31. In first month or two of ownership I could pull nearly 25 knots at full power. Last sunday I could only make about 17.5kts. At this point my "HOPE" is that it is growth on the bottom - though it doesn't look that severe. I can still get over 3000 rpm and my oil filters were both recently changed. I had many pax onboard this weekend so I hope to try again with a smaller number aboard in the near future.
 
I have 2014 Cutwater 28 that has about 60 hours on it. On my second tank of diesel, although this boat was demo'd at a couple shows, so it's probably the third tank. I have not used additive yet, although I will on the next fill. I have not experienced this slowing problem. Here's the difference I think I have. I keep my boat on a lift. The bottom and running gear are clean and clear. Once I get going, I typically run around 3,000 RPM in the Chesapeake Bay doing around 18k, depending on wind and tide action. ?

I can still go WOT and 3500 RPM, about 23.5 k, maybe 24k if I trimmed just right. But, I don't believe I have ever seen 25knots. My experiences are with 2 to 4 people 2/3 to 3/4 fuel, full water.

Alan
 
SWE67, I still recommend you do the full throttle test with the transmission in neutral.
These engines are electronically governed to keep them from over speeding. You need to know that there is not an electronic gremlin limiting you to 3000 rpm :mrgreen:
 
Hopefully SWE67 will let us know if the bottom cleaning restored his speed or if the cause remains elusive.
 
When I put it in "throttle only", the RPM limits to 1500....I picked up a fuel filter....What is the part number for the pre-filter? They put the label up against the bulkhead side and it is essentially unreadable.......When I picked up the filter at my local Volvo service marina and described the problem, they put cold water on the fuel filter idea as it is running smoothly up to the 3000ish RPM new limit. They said it didn't sound fuel starved....Sounded like no boast from the turbo......Who is the closest Volvo/Cutwater service center in Old Greenwich CT?
 
Not sure about the Volvo, but on my Yanmar I have had trouble with my vacuum line popping off and then not being able to reach top RPM. However, I do get an alarm telling me that I have a problem. You may want to check to see if your turbo is the same and make sure all the lines are connected.
 
My Volvo d6 does the same - 1500 rpm limit in neutral. I know my running gear is dirty (will get cleaned this week). I also have small growth on my prop which I believe is affecting my speed.
 
Next time you run your boat after changing the fuel filters. Check your boost on your turbo, if it were a boost issue you would not be able to pull more that 1750 rpm. This to me still sounds like a fuel issue.

Primary Fuel filter P/N 861014
Secondary Fuel filter P/N 3583443
 
Hopefully one of us can solve this mystery as you have described the exact same problem we are having with our R29
 
Me too with our R-31
 
Just a thought. Has anyone with this problem (yanmar or Volvo) checked their air filter and its pathway for blockage?
Don,
 
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