Low Power – QSM-11

[Glenn Niccolai]

 

NJ Boat, dropped 2 weeks ago (fresh bottom paint and props tuned up over winter) zero growth. First run was fantastic, 24 knots, no problem (RPM’s fuel burn 17 /18  GPH, 1875) hitting numbers, no issues) – WOT – 2325-2360

 

 Took boat out last week, – 20 mile run – 3 miles trolling –  1850 RPM – 20/21 GPH and 19/20 knots…. A full 4 to 5 knot drop… WOT – 2250.. both engines read identical.. both engines ran smooth, no stuttering. Read your article,  Engines Power / Props Move Boat.  

 

 Fuel – We changed fuel filters (both where clean, no build up etc).. we ordered air filters from you.. haven’t arrived, we felt we needed new ones anyway.  

 

 Thoughts?

 

Topic

[Tony Athens]

Glenn,

Sorry for the late reply–Just been super bust and I needed to read thru it all a few time..

Your numbers (GPH at particular RPM) are all over the place and I do not have a solid answer than this………………..But I will say this with 100% confidence..

1) GPH readoust can vary some (or a lot) just because of the way it in measured.. It’s an “algorithm” based on many parameters the the ECM gets input from various senders and transducers.. Things like RPM, Boost, fuel restriction which affects internal throttle position, fuel pressure after the on-engine fuel filter, IMT, and others which I’m not privy too.. Is so many words, sometimes it’s really accurate and other times, is can be BOGUS.. Change a fuel filter, the the numbers can change, something by 20+ %..

2) Engine RPM vs. actual vessel speed………This is exact but can vary greatly because of the particular conditions that the vessel is running under at that time…… An, d without any doubt, those conditions vary way more than most will accept……………………Do I really need to go into the list of those things? Just think about how you are measuring speed–I’m assuming a GPS, right? Real vessel speed is WATER SPEED as that is the medium that the engine “sees”, not ground speed.. Think about that a bit..

Based on the numbers you have posted, you are propped above the upper edge of what I’d recommend, but certainly better that many or most..

Any manifold leaks?

Any sluggishness getting up on a real clean plane to you final happy vessel cruise speed? Notice I did not mention “happy Cruise RPM”–Big difference..

Also, how important is your vessel speed above 2100 RPM?

Tony

[Glenn Niccolai]

UPDATE – RPM – FUEL BURN

Tony,

Here is my follow up, as I was able to run the boat through all the RPM curves. Please see below:

1300 – 10 GPH
1400 – 11.7 GPH
1500 – 13.5 GPH
1700 – 16.5 GPH
1900 – 19 GPH
2100 – 22 GPH
2300 /2350 – 29 GPH (i place 2350, as that is the top off with the RPMS)

1/2 tannk of fuel (300 Gallons) and 1/2 Tank of water – (75 Gallons) – 2 People On Board. 41 Luhrs -2005…

I hope this helps..

[Glenn Niccolai]

Follow up QSM low power

Was at the boat yesterday.. ran.. here are numbers

3 weeks ago:

RUN: 23.1 knots 1920 18.9 GPH (this is accurate, i took a pic)
WOT: 31 Knots – 2325 RPM 29 GPH (Best I could remember)

Boat Set Up – 2 People – NO water on board (hold 150 Gallons)

We had multiple runs (could not go in ocean, had to run river… which is about 1 mile long before you have to come off plane.. a bit limiting)

Yesterday

First Run: 23.4 knots 1890 RPM 17.5/18 GPH
2nd Run: 23.9 knots 1930 RPM 18.7/GPH
WOT – 30.5 knots 2350 RPM 29.9 GPH

3 People (full water -150 gallons.. however about 75 gallons less fuel)

Hope that helps tony.. i do have your prop curve chart.. seems we are off a little by those numbers. I really would have liked to have run boat in the ocean but i could not, too rough. However will try this weekend and will have your prop chart with me to take ACCURATE numbers THROUGHOUT the RPM RANGE as noted on the prop chart.

[Glenn Niccolai]

qsm-11 – slow speed

i will be on boat today and will be able to run and get exact numbers..

[Tony Athens]

Glenn,

You came here for an answer, correct?

No input as to exactly what I asked for or need = no answer = and no solution as to why

You decide…………………Remember, the word I used “ACCURATE”..

We both know each other from way back.. You should know me by now–I am 100% Black & White with ZERO grey on something like this.. I expect the same from someone that asks a questions and expects an answer, or we are both wasting our time..

Your move..

Tony

[Glenn Niccolai]

1) 1st run——————-Vessel speed and GPH at 1875 RPM ??? – 24knots.. 17 gph @ 1875
———————————WOT RPM, speed & GPH was ??? – 31 Knots, GPH – did not look
just dropped from winterizing.. no water, full fuel, 2 people

2) 2 to 3 week later or now Vessel speed & GPH at 1875 RPM=?? – 19/20 Knots – 19/20
—————————————WOT RPM, GPH and Vessel peed=?? 27 knots, did not look
note: No smoke.. black or Gray, ran clean
full water, 5 guys..

Since we have noticed the above, we cleaned fuel filter, did not notice ANY bad fuel / contaminants… Air filters appear to be cleaned.. In addition, we BELEIVE we did not hit anything that would damage the props..

[Tony Athens]

QSM Vessel Performance issues

Glenn,

Sorry for the late response..

Get me straight on this:

1) 1st run——————-Vessel speed and GPH at 1875 RPM ???
———————————WOT RPM, speed & GPH was ???

2) 2 to 3 week later or now Vessel speed & GPH at 1875 RPM=??
—————————————WOT RPM, GPH and Vessel peed=??

SAME exact fuel, added “stuff” etc etc etc?

BE ACCURATE!

Tony

[Author]

Replies