RPMs... lets not beat a dead horse <Max RPMs for 190 boats?>

[Englewoodcowboy]

OK, new owner of a yamaha AR192. Out of the box the motor would only rev to 7000 rpms and do approx. 42 mph. When I took the bimini top down it would do 7200 rpms with a top speed of 44mph. As of today I have ran 1 full tank through it and been out for 2 days. I checked the throttle adjustment and there was approx. 1/8" gap at WOT. I have adjusted it today so there is maybe .015 gap at WOT to avoid excessive stretch or bottoming out the electronic throttle but will not be able to run it till this weekend. I am running my boat at approx. 1400 to 1700 feet ASL depending on which lake I am on. I am not looking for it to be spot on as I know there will be variations from one to the next due to MFG tolerances etc. I am not looking to get what is stated but what others have seen as real world experience. I have zero complaints with the motor at this time as I also know that re-pitching may need to be done to compensate for elevation etc. if I feel like the hole shot is lacking etc. I have pulled a tube with it so far and was happy with how it pulled the rider up. What I would like to know is:

1) What is the max RPM our engines are set to rev to.
2) At the stated elevation, what should I realistically expect for performance since I will not have an At Seal Level experience to compare to.
3) Are there any other items I should check and or adjust to make sure it is running at its best performance?

 

[txav8r]

Your close to max RPM at 7K+. As for speed, I don't know what max is on the 192 but I think it is mid 40's, maybe a few mph above in perfect conditions. The bimini top will make a big difference, as will the load in the boat. Anything under 1500-2000' elevation can be considered pretty close to sea level in terms of performance. I don't have and haven't seen a graph to indicate a linear drop of performance, and it isn't linear anyway. But it would be reasonable to consider maybe an mph drop per 1000' up to 3000' and then a much steeper loss above that. I don't think you should adjust anything else, but read other 192 stated performance and divide by a fudge factor. Wind/waves/max load/position of load/age of engines/bimini/temperature/humidity...they all play a role in performance on our boats. I can't imagine the bimini affecting the rpm of the engine too much, although a static engine with the pump not moving through the water has more restriction and won't spin out as high as a pump running through the water at speed. But the difference of bimini position on the speed bimini up or down is not going to affect the engine speed IMO. But...I typically see 7000 rpms or thereabouts and it isn't up higher unless I let the engines wind on on smooth water and see the speed get higher, then the engines climb with the speed. That last little bit takes more time to eek out than the first 7000 revolutions. Hope this helps!

 

[Englewoodcowboy]

It does help and thank you for some insight. I do know the factor of wind, sea condition, load etc. all play a part. I know on the other forum people seem to be hung on a certain rpm number and speed and that is not what I am trying to achieve by any means, just more knowledge. I know with past boats I have had to play with the prop pitch etc. to get the motor dialed in and it helped some with the economy. Was just wondering the same on this. I am not too worried about its fuel burn as others, it is a BOAT and playing costs $$ but to be sure it is running how it was intended and not having unreasonable expectations of it is a huge help. I have no desire to run at WOT everywhere I go, seems to be a nice cruise/noise level etc at around 25 to 30 mph and around 6000 to 6500 rpms. I am amazed at how fast it falls off of speed within a few hundred rpms vs. a prop driven boat. Seems like you have to be at 5000rpm or better to be above a few mph. Guess that is the nature of a jet though.

 

[txav8r]

I am amazed at how fast it falls off of speed within a few hundred rpms vs. a prop driven boat. Seems like you have to be at 5000rpm or better to be above a few mph. Guess that is the nature of a jet though.

This is very true on all of the Yamahas. It is in the torque and hp range of these engines. It doesn't develop hardly any until they reach the upper 1/3 of the rpm range. The 19'ers are a different animal, but I am guessing this is true of them as well. Just lots of noise and not much movement until you get on plane and in the upper 1/3 of the rpm range.

 

[ACRDSPORT14]

Hit 45 on gps tonight on my 190 49 on my speedo

 

[bucks448]

The max RPMs on a 1.8l NA or SC is ~7800RPM, but a lot depends on conditions and load. AtSL, I'm turning 7400-7600RPM depending on conditions and running at a max of 45MPH. If you're normally Above SL (significantly), I'd consider re-pitching the impeller.