2015 Yamaha AR192, Loss of Power

[jetboater40]

Good morning!

We are the owners of a 2015 Yamaha AR192 and have been for the past five years.

I read many posts that detail the boat should reach a maximum speed of approximately 48mph.

Late last summer, I could only reach 30mph at 7500rpms.

I never previously tested the full speed and so I only have last summer's maximum speed as a reference.

I presumed it was because of the accumulation of river algae under the boat (it remains in the water for the summer).

The underside was pressure washed in the fall of last year, as it is every year fall.

The boat was launched last week and shortly thereafter, I tested the speed.

I reached 35mph at 7500rpms, once again below the advertised speed.

The water temperature was 18 degrees Celsius and the ambient temperature was 18 degrees Celsius.

I am waiting for the fogging oil to burn off completely before replacing the spark plugs.

The air filter looks clean, although I cannot fully access it because of all the connected pipes.

The impeller is smooth and there is no obstruction(s) in the grate.

Onboard was one adult and one child.

The petrol tank was full.

The water pilots (water pissers) are operating normally.

Apart from the spark plugs and maybe the air filter, any thought(s) as to why I cannot reach a speed above 40mph?

Thanks!

 

[LakesideLaw]

Where are you located? Update your info to include where you are at as elevation and other factors will impact speed.

 

[Crob83]

How long since you last changed the plugs? Is your fuel old?

 

[jetboater40]

Where are you located? Update your info to include where you are at as elevation and other factors will impact speed.

We are located 70m (230ft) above sea level.

I doubt the location of our City is affecting the performance?

 

[jetboater40]

How long since you last changed the plugs? Is your fuel old?

I changed the spark plugs this week and tested the speed...almost the same result, very minor increase in speed.

The petrol is from last fall.

However, I stabilised same with petrol stabiliser.

When I tested the speed last summer, it was new petrol.

 

[D3nN1s]

Sounds like the super charger is not kicking in? Had a similar issue with my 2015 Ar192 last year at about 220 hours. They replaced the Supercharger Clutch under warranty.

 

[jetboater40]

Completely unsure.

The boat will get up to speed quickly and maintain a constant speed.

The RPMs remain constant as well.

Presumably, a failing clutch will cause the RPMs to spontaneously decrease?

We have approximately 100 hours.

 

[ScottS]

We are located 70m (230ft) above sea level.

I doubt the location of our City is affecting the performance?

If you were at a high elevation with high air temperature and high relative humidity, the boat loses functional horsepower.

When you are doing your speed test, minimize weight in the bow.

Regardless of all of this, I would expect you to reach at least 40 mph. Fresh fuel may help. Ensuring that your intake/pump properly sealed can help, although I would expect you to have an issue with cavitation at launch under wide-open throttle if it is too bad.

 

[Crob83]

I would check the supercharger clutch just to rule it out

 

[DrPhil]

How does one check the supercharger clutch?

 

[jetboater40]

Remove the intake and determine if it spins in both directions?

I understand it should only spin in one direction.

Also, there should be some resistance when attempting to spin it with your finger.

Am I correct?

 

[jetboater40]

We were on the boat this morning and to verify the speed, I downloaded a GPS speedometer app to my iPhone.

Once underway, I noted the speedometer displayed 32mph when were at 38mph (61kph) at 7200rpms.

Onboard were two adults and two children and 3\4 of a petrol tank.

It was very warm, however, so I suspect heat soak may have contributed to a decrease in performance.

Nonetheless, it appears the speedometer is not accurate after all.

How can I adjust \ repair \ calibrate same?

 

[ellj]

Did you ever fix this? @jetboater40

 

[jetboater40]

I tested the speed again last week / weekend and the speedometer appears to now be accurate.

Perhaps when I tested the speed 6 June 2021, the undercurrent was preventing an accurate reading.

Otherwise, the maximum speed achieved with two (2) adults and two (2) children was 38mph (61kph).

That same speed was also achieved with one (1) adult and one (1) child.

The speed remains consistent despite the ambient / water temperature and the number of passengers.

The engine noise is normal and all other aspects are normal...go figure!