RPM's for 1.9L's

[jcb1977]

What is everyone seeing for top end RPM's with the new 1.9L's? mine seem to top out at around 7300 right now. wondering what everyone else is seeing and if I need to check a few things if i'm low.

 

[anmut]

Sounds low - my 1.8's get to 7800 WOT

 

[Michal]

@jcb1977
According to boattest.com they got 7800 WOT on the 252 they tested. I had an issue with low RPM a few years ago and had to adjust the throttle cable. I followed the video from @JetBoatPilot

Boat test where they are showing 7800

JetboatPilot throttle adjustment.

 

[FSH 210 Sport]

Temperature and altitude also play a critical role in engine performance. What was the temp and altitude you were at?

 

[Marvin willis]

Boat or ski?

 

[jcb1977]

Temperature and altitude also play a critical role as n engine performance. What was the temp and altitude you were at?

800’ above sea level. Temp was 75 degrees

 

[jcb1977]

@jcb1977
According to boattest.com they got 7800 WOT on the 252 they tested. I had an issue with low RPM a few years ago and had to adjust the throttle cable. I followed the video from @JetBoatPilot

Boat test where they are showing 7800

JetboatPilot throttle adjustment.

I’ll take a look at my throttle cables. Oil level is midway between full and add holes.

 

[FSH 210 Sport]

800’ above sea level. Temp was 75 degrees

I’m curious, what octane fuel are you running?

I looked at the weather data from a few days ago from your location to get the altimeter setting and dew point / relative humidity for a 75° day.

You can see from the chart below that your 800’ above mean sea level (MSL) on that day was actually 2194’ as far as the engine was concerned, looks like a hp loss of 2.2% or 4.4 hp per engine. In my opinion not enough to account for a 500 rpm loss but still something to be considered.



Note: I saw a Berkeley Jet Hp demand curve a couple of years ago that showed for that particular pump the hp required to spin that pump at 5000 rpm was 375 hp, to spin the same pump at 6000 rpm required 735 hp. So you can see there is an exponential rise in hp demand as the pump reaches peak performance.

 

[jcb1977]

I use premium with no ethanol. Not sure what octane that is.

 

[FSH 210 Sport]

I use premium with no ethanol. Not sure what octane that is.

Thats great you are using non ethanol fuel, usually premium is 91-93 octane. I’d check your owners manual to verify the following, the normally aspirated engines usually require 86 octane. Contrary to some popular beliefs 91 octane does not have more power than 86 octane, in fact if 91 octane is used in an engine that only requires 86 octane that engine will produce less power and run hotter than it would if using 86 octane, because the 91 octane burns slower than the 86 at the lower cylinder pressure of a normally aspirated engine versus the higher cylinder pressure of the super charged engine that requires the 91. In addition you are also spending more money on fuel than you need to.

I run non ethanol fuel as well, but I mix 85 and 91 in the correct proportions to get 86.
I use this calculator. Octane Mixture Calculator

If you do not have access to 85 or 87 non ethanol you can run ethanol fuel just be sure and use Star Tron at each fill up to make sure the ethanol fuel doesn’t get phase separation. I will run ethanol fuel if that is all that is available at a destination I’m at then run all of that out once I get back home and re fill with non ethanol.

 

[anmut]

Thats great you are using non ethanol fuel, usually premium is 91-93 octane. I’d check your owners manual to verify the following, the normally aspirated engines usually require 86 octane. Contrary to some popular beliefs 91 octane does not have more power than 86 octane, in fact if 91 octane is used in an engine that only requires 86 octane that engine will produce less power and run hotter than it would if using 86 octane, because the 91 octane burns slower than the 86 at the lower cylinder pressure of a normally aspirated engine versus the higher cylinder pressure of the super charged engine that requires the 91. In addition you are also spending more money on fuel than you need to.

I run non ethanol fuel as well, but I mix 85 and 91 in the correct proportions to get 86.
I use this calculator. Octane Mixture Calculator

If you do not have access to 85 or 87 non ethanol you can run ethanol fuel just be sure and use Star Tron at each fill up to make sure the ethanol fuel doesn’t get phase separation. I will run ethanol fuel if that is all that is available at a destination I’m at then run all of that out once I get back home and re fill with non ethanol.

Per my manual 87 with 10% ethanol is totally fine to run, which is what I put in my two 1.8s without issue. However I always fill it at the end of season with premium non-ethanol and treat to lower the chance of water absorption.

 

[jcb1977]

Per my manual 87 with 10% ethanol is totally fine to run, which is what I put in my two 1.8s without issue. However I always fill it at the end of season with premium non-ethanol and treat to lower the chance of water absorption.

my manual for the 1.9's calls out minimum octane rating of 86 with up to 10% ethanol.

 

[FSH 210 Sport]

my manual for the 1.9's calls out minimum octane rating of 86 with up to 10% ethanol.

There you go…. Save yourself some dough at the very least.