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Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 16107
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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Johnson 150 only turning 3900 rpm max while burning 16

Customer Question

Johnson 150 only turning 3900 rpm max while burning 16 gallons per hour
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.
Hello my name is ***** ***** am I speaking with? What is the year/model number on the engine?Have you ever seen this engine make full power before, if yes, how long ago was that?How old is the fuel?Have you done any testing on your own yet, if yes, what have you done?Lastly, what kinds of questions did you have for me?
Customer: replied 1 year ago.
Hi Jason,
It is a 2001 Johnson 150 model J150VXSIF
The motor is new to me, no prior experience with it.
The fuel is fresh rec 90
She is premix
I have already done the following:
Rebuilt all 6 carbs and adjusted floats
replaced all 6 coils and power pack, along with wires
New spark plugs gapped correctly
Checked buttery on each carb for full opening.
Changed prop from 15 X 16 to 14.75 X 17 no real difference.
Changed tach to test.
The boat is a light Logic 21ft
She maxes out at 32 mph at 3800-3900 trimmed all the way
At 3000 rpm she is doing 23 mph Per GPS
I installed a floscan unit to measure fuel consumption, as in description, she is burning 16 gallons per hour wot
Customer: replied 1 year ago.
That's "butterfly" :) on the carbs...
Customer: replied 1 year ago.
She starts and idles fine also
Compression is also good on each cylinder
90-100 on all
Expert:  Jason replied 1 year ago.
Is the boat a center console? I'll run some prop math. Do you have a portable tank that you can run the engine on?Was the oil side of the VRO disabled, or was the VRO changed out to pulser style pumps?
Customer: replied 1 year ago.
VRO was disabled, I have been doing my testing on a portable tank with fresh fuel and oil.
I have already read many of the boat test reviews of the same boat with the same motor, she should be running in the mid 40's turning 5500 rpm...also confirmed this with the Logic boat forum owners...
Expert:  Jason replied 1 year ago.
Got it. The next question is I saw that you replaced quite a few of the ignition parts. Have you actually checked spark output by hooking a timing light up to each plug wire one a time and seeing if the light flashes or not?
Customer: replied 1 year ago.
yes, I hooked up a spark tester to each, all the same result, I also removed each cable one at a time while both idling and under load and could hear the drop.
Expert:  Jason replied 1 year ago.
It's possible the VRO is bad, and not pumping enough fuel. What you would want to do is test the VRO next to see if it's any good or not. I'm attaching a PDF file that explains how to test the pump. Give it a read and let me know what you think.
Customer: replied 1 year ago.
No VRO, it was removed.....fuel flow is showing 16 gallons per hour WOT, that is about what the max would be for a Johnson 150 2 stroke...
Expert:  Jason replied 1 year ago.
I asked if the VRO was disabled or changed out, you said it was disabled. Now you wrote that "No VRO, It was removed". I need to know which it is. What style fuel pump is on this motor, and how many fuel pumps does it have, 1 or 2 or more? Also, your fuel economy estimate is not correct. These are EXTREMELY thirsty engines. An Etec 150 will drink 15 to 16 GPH at full throttle. The carb'd engine is going to drink 20 to 22 (possibly more)
Expert:  Jason replied 1 year ago.
We can also do this over the phone if you want to do it that way, it usually goes a lot quicker.
Customer: replied 1 year ago.
Hi, if we do the phone call is it another $26.00?
Expert:  Jason replied 1 year ago.
Yes correct. It is a premium service not included in your initial deposit. On the other hand, it is a flat rate, and it doesn't bill per minute like a 900 number would. Whether it takes 5 minutes or 1/2 an hour, its still the same extra 26. If you would like me to give you a call, you can accept the offer. If not, we can continue online.
Customer: replied 1 year ago.
Based on every forum I can find regarding fuel consumption max for the same motor from owners with flo scans I see the average of 14-16 gallons per hours max. I can't find one person who has the same motor who claims higher than that?
But I also have looked down the throats of the carbs while running WOT and can see the fuel spray for each..all the same (a lot)
Customer: replied 1 year ago.
Lets just continue for now....
Customer: replied 1 year ago.
Also 1 fuel pump...
Customer: replied 1 year ago.
http://www.boats.net/parts/search/BRP/JOHNSON/2001/J150VXSIF/FUEL%20BRACKET%20&%20COMPONENTS/parts.html
Expert:  Jason replied 1 year ago.
What you want to look up is what an Etec gets for fuel economy. For example, click this link below, these are average fuel economies for Etec engines. http://www.boat-fuel-economy.com/evinrude-outboard-fuel-consumption-us-gallons Etec's get anywhere from 25 to 40% better fuel economy over carb'd engines. You can multiply that 15.1 by 1.25 to 1.40 to give you an idea of what a carbed engine will burn. I have a Mercury 150 personally (carbed) and that engine burns 20-21 at full throttle with a 4 bladed stainless prop. That being said.... Which fuel pump is on the engine, #37 on the boats.net diagram?
Expert:  Jason replied 1 year ago.
I'm going to have to leave in about 5 minutes to meet some friends for dinner. We can pick this up later tonight or tomorrow. Or try to wrap this up now if we can be quick enough. In a nutshell if you have just 1 fuel pump that's not going to be enough to deliver enough fuel volume to the carbs. On any JRude/OMC engine with a VRO, if you want to get rid of the VRO what you do is plumb the engine the same way it used to be before the VRO pumps came out. Click this link below, this is for a 1983 Johnson 150.http://www.boats.net/parts/search/BRP/JOHNSON/1983/J150TXCTB/FUEL%20PUMP/parts.html You'll notice it runs two fuel pumps. On the older V6 engines, before the VRO was invented, OMC used 2 fuel pumps to deliver the proper amount of fuel to the engine, just 1 pump will not cut it. Does that make sense to you?
Customer: replied 1 year ago.
Lets try tomorrow, I also have to go to dinner.Have a good evening.
Expert:  Jason replied 1 year ago.
I have to run for now, but i'll be back in a few hours. We can pick this up then. You have a good evening as well.-Jason
Customer: replied 1 year ago.
Oh and the motor is a 2001...
Expert:  Jason replied 1 year ago.
Got the year. When you gave me the model number I ran that first so I knew what you had. Reply back when you are ready ad we can continue on.
Customer: replied 1 year ago.
Hi Jason, I am back...
Expert:  Jason replied 1 year ago.
Hello. I don'' know your first name (I asked but you never told me) Where you able to see my reply from yesterday at 644pm?
Customer: replied 1 year ago.
Hi, yes, I did, don't think it is a fuel flow issue though, the primer bulb is nice and firm when running WOT, even if I pump it while running, it makes no difference.
Oh, and I'm Steve
Customer: replied 1 year ago.
I was told that the power head is a newly rebuilt one that the old one had blown due to a VRO pump failure, so they put the new powerhead on and removed the VRO tank, so the motor is premix now.
Expert:  Jason replied 1 year ago.
Hi Steve. There is only way to find out and that is to hook up a fuel pressure gauge to the output side of the pump, run the boat at full speed, and check the fuel pressure. It needs to be 3 psi or better. If it's not, there is a fuel pressure issue. Is that something you can do?
Customer: replied 1 year ago.
I would have to buy a pressure gauge....
Customer: replied 1 year ago.
Can you show me a link to one on Amazon...something inexpensive would be great
Expert:  Jason replied 1 year ago.
Something like this would work http://www.amazon.com/Actron-CP7802-Vacuum-Pressure-Tester/dp/B000CPINHA/ref=sr_1_sc_1?ie=UTF8&qid=1463341769&sr=8-1-spell&keywords=fuell+pressure+vacuum
Customer: replied 1 year ago.
Funny, that is the same exact one I was looking at...
I will order it and report back, if the pressure is above 3 psi, then what should I look at?
Expert:  Jason replied 1 year ago.
Well... Now that you've said the powerhead has been rebuilt coupled with the fact you've never seen this engine make full power..... If fuel pressure is good I would tear apart the carbs first just to make sure they have the correct jets in them, and that it's not jetted for high altitude or something like that. After that, the block would have to come apart to see if the person that rebuilt this installed a piston or two backwards. Wouldn't be the first time I've seen it.
Customer: replied 1 year ago.
I rebuilt all six carbs and checked all the jets, correct on all...
Customer: replied 1 year ago.
And I don't have any proof the powerhead was rebuilt, just what the person I bought it from said he was told....so 3rd party info...
Expert:  Jason replied 1 year ago.
Gotcha. See what your fuel pressure is, that's all you can do for now
Customer: replied 1 year ago.
Will do and get back to you in a few days...
Expert:  Jason replied 1 year ago.
sounds good, keep me posted