23' 255 FSH - Boat will not go past 47mph!!!

[pariseng]

Hi there wondering if anyone has had this issue. Came to the Florida Keys where there's beautiful flat waters so decided to max out the speed on my FSH and it will not pass 47mph.. I find this odd where everywhere it says these boats go mid 50's. I checked for seaweed/obstructions to make sure it was clear, checked to make sure there was nothing upstructing the impeller, even checked to see if the superchargers are properly spinning only one way, everything is fine. I just filled up the boat with Rec 90 gas. Does the lower octane make a difference or do I need to take it to the dealer?? Let me know what you think..

 

[TimW451]

You definitely need the right octane to get top speed. 93 for an SVHO. Need to start there.

 

[pariseng]

You definitely need the right octane to get top speed. 93 for an SVHO. Need to start there.

Yeah, is what I was thinking too.. thx.. I'll give it a try. Since everything else is working perfectly fine, no check engine code or any smoking guns..

 

[lazergeek]

Hot and Humid air caues horsepower loss mimicing high altitude. keys have been 90-95 degrees for weeks.

 

[Cobra Jet Steering LLC]

Yes!! I get much faster speeds in the winter but when the air and water heat up the speed drops thus the reason they make intercoolers for super charged engines.

 

[FSH 210 Sport]

What rpm’s are your engines turning at WOT?
What was your fuel load?
How much weight did you have on board, people and gear?
What is the max speed when you’ve driven the boat elsewhere and where was that at? Have you ever seen those mid 50’s speed numbers? What was the Elevation and Temperature?

Per @lazergeek ’s suggestion, using yesterday’s data you are at a density altitude of 2376’, which results in a 6.77% HP loss, or a 33.85 HP loss.

 

[anmut]

Was your motor just warming up when you tried this or was it already heat soaked from previous boating?

 

[pariseng]

Hot and Humid air caues horsepower loss mimicing high altitude. keys have been 90-95 degrees for weeks.

Yup.. It feels like 100 degrees..

 

[pariseng]

What rpm’s are your engines turning at WOT?
What was your fuel load?
How much weight did you have on board, people and gear?
What is the max speed when you’ve driven the boat elsewhere and where was that at? Have you ever seen those mid 50’s speed numbers? What was the Elevation and Temperature?

Per @lazergeek ’s suggestion, using yesterday’s data you are at a density altitude of 2376’, which results in a 6.77% HP loss, or a 33.85 HP loss.
View attachment 203071

Wow.. great info.. well, I was by myself, no load from gear, half a tank of fuel, about 6,400 rpm.. I don't get to 7,000 rpm.

 

[Dixemon]

Wind direction, current and how the boat is loaded down also huge contributing factor.

 

[FSH 210 Sport]

Wow.. great info.. well, I was by myself, no load from gear, half a tank of fuel, about 6,400 rpm.. I don't get to 7,000 rpm.

Check your oil level and air filters. Your oil level may be high, and your air filters may be fouled with oil. You are missing 1000 rpm’s. You may need a set of spark plugs.