255XD RPM and Top Speed Issue?

[wildtwins]

Hello all,
I have a 2022 255xd with about 50 hours of use. The last two times I've gone out, I've noticed that the RPM's at WOT are off by about 500rpm. Starboard is the motor with the lower RPM's. At half throttle, the rpm's seems to match. It also seems that my top speed has gone down. For example, yesterday, I had 90% fuel and 3 adults and could barely hit 40mph. This all might be normal, but wanted to get the opinions of the experts on this forum weigh-in.

 

[anmut]

That seems low. I'd start with your pumps 1) inspect while they're in from the bottom for anything caught on the shaft, look for dings in the blades, and inspect the tunnels for missing sealant. 2) Pull the pumps and look for any damage.

 

[HangOutdoors]

Hello all,
I have a 2022 255xd with about 50 hours of use. The last two times I've gone out, I've noticed that the RPM's at WOT are off by about 500rpm. Starboard is the motor with the lower RPM's. At half throttle, the rpm's seems to match. It also seems that my top speed has gone down. For example, yesterday, I had 90% fuel and 3 adults and could barely hit 40mph. This all might be normal, but wanted to get the opinions of the experts on this forum weigh-in.

Where are you boating? What is the altitude. Was the humidity and temperature high?

 

[lazergeek]

What @HangOutdoors said, altitude or hot humid day could be the culprit. replacing spark plugs is next. Its not a pump issue as that would cause higher RPM's not lower.

 

[anmut]

What @HangOutdoors said, altitude or hot humid day could be the culprit. replacing spark plugs is next. Its not a pump issue as that would cause higher RPM's not lower.

Unless he's got something stuck on his pump shaft, or between the aft impeller and the nose cone...

 

[CraigAR]

Check oil levels and also check your air filters.

 

[lazergeek]

Unless he's got something stuck on his pump shaft, or between the aft impeller and the nose cone...

True but that usually causes more issues at low speed which the OP states just at full throttle.

 

[Ronnie]

Is your boat in the water? If so and it’s not on a lift I think you should see if there is any scum built up under the water line.

 

[wildtwins]

Is your boat in the water? If so and it’s not on a lift I think you should see if there is any scum built up under the water line.

Yes, it's in a wet slip. Can scum buildup, under the waterline, really effect speed that much?

 

[wildtwins]

Where are you boating? What is the altitude. Was the humidity and temperature high?

In Minnesota. Temp was 75 and humidity was low.

 

[HangOutdoors]

Yes, it's in a wet slip. Can scum buildup, under the waterline, really effect speed that much?

Yes. Couple that with humidity and Temperature and you could significant speed.

 

[HangOutdoors]

In Minnesota. Temp was 75 and humidity was low.

If your plugs are good and you didn't just overfill oil and your air filters don't have oil in them and are clean, as well as nothing is in your pumps, I would agree with @Ronnie..... You may have some build up on your hull.

 

[adrianp89]

I would check under boat. A few weeks ago I did a trip to Anclote. I could run WOT but my speed kept getting lower. When I got it out of the water, there was a bunch of seaweed stuck around the grates. I couldn't tell from the clean out ports.

 

[FSH 210 Sport]

I don’t know if the loose insulation moving over under power and blocking the intakes in the engine bay is a thing on the 255 XD, but that has happened on some other late model boats with the 1.8’s.

Check all the insulation in the engine bay anywhere near the air box intakes to make sure it is secured to the bulk head.

 

[crazy4life]

Keep my boat wet slipped for 6 months and it is definitely slower in October then April. You would be amazed how much algae buildup affects top speed. Probably loses 10 mph over the season. No big deal for me because 40 is fast enough for me.