17 Ft Mako 140hp Johnson 4500RPM?!

walleyehed

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Jun 29, 2003
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I doubt that's an issue. Lund has many of their boats with built-in tanks in the front with 10-15ft of fuel line. It's not an issue and if it were truly restricting it, it would have burnt a hole in a piston by now. It may surge if a restriction exists, but it won't run at a constant rpm if restricted.
Chris, fuel pump/s starting to get weak will cause the engine to want to fall on it's face when you pour the power to it such as getting on plane almost like it's going to die.
 

Chrisravosa36

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Aug 16, 2015
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I doubt that's an issue. Lund has many of their boats with built-in tanks in the front with 10-15ft of fuel line. It's not an issue and if it were truly restricting it, it would have burnt a hole in a piston by now. It may surge if a restriction exists, but it won't run at a constant rpm if restricted.
Chris, fuel pump/s starting to get weak will cause the engine to want to fall on it's face when you pour the power to it such as getting on plane almost like it's going to die.
Also forgot to mention that at one point, I was running WOT than slowed down quick to go through a tunnel and the motor idled down and died, it took 30 seconds to get back going, I had to pull the ball and she started back up. Im going to take a look at the pumps tomm. Il see what they look like and report back.
 

Fed

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Also let me explain the current situation ive got with fuel. I have two 12 gallon tanks that have 2 ft of line that connects to a y spliter, another 10ft of line under and around the deck, to the fuel water separator, then 6 inches to the pressure value, then the primer bulb, up to the fuel pump at that point. Could this be a lack of fuel situation? is the engine starving?
I'm guessing that value is a valve, what is it and why is it there etc? Not a breather valve is it?
 

Maclin

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May 27, 2007
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Wow, that does seem like a lot of plumbing for the average OB fuel pump to draw through. Lots of places for an air leak also, just sayin'.
 

Chrisravosa36

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I'm guessing that value is a valve, what is it and why is it there etc? Not a breather valve is it?
[h=1]Attwood Fuel Demand Valve,[/h]
also just to be certain, the breather vaulves on the fuel tank should be open during operation of the outboard/
 

Chrisravosa36

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Wow, that does seem like a lot of plumbing for the average OB fuel pump to draw through. Lots of places for an air leak also, just sayin'.


I need the fuel/water sep. I also need the primer bulb. I could get rid of the fuel demand valve. Also forgot to mention the fuel line goes through a culvert down to the bildge from the center console than up to the transom to the fuel water serp.


This is the line im using [h=1]HBD Thermoid NBR/PVC SAE30R6 Fuel Line Hose, 3/8" x 25' Length, 0.375" ID, Black[/h]
Do you think id need a bigger diamater?
 
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Sea Rider

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Sep 20, 2008
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Did OB performed OK with portable tank hoocked direct to OB's fuel connector ? If so, there's an issue with the rest of the fuel lines. For peace of mind I would disassemble internal fuel valve components and check them out. If diaphragam is excessively ballooned, dried, change. Usually need to change 2 gaskets/1 diiaphragm, no need to buy the whole pump unless price is very close to those parts. With long fuel lines pump must do its homework right.

Happy Boating
 

Chrisravosa36

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Did OB performed OK with portable tank hoocked direct to OB's fuel connector ? If so, there's an issue with the rest of the fuel lines. For peace of mind I would disassemble internal fuel valve components and check them out. If diaphragam is excessively ballooned, dried, change. Usually need to change 2 gaskets/1 diiaphragm, no need to buy the whole pump unless price is very close to those parts. With long fuel lines pump must do its homework right.

Happy Boating


im am testing that today, il see how it runs with an test tank. also Ive already ordered new fuel pumps. Im sure these pumps were hard at work before, because the previous owner had a even bigger boat.
 

Chrisravosa36

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Ok today I couldnt head to the lake, because they called me in to work, and I need the money. Tomm is another day off and I will be taking it to the lake. Ive done a few things to it today.


#1 Checked fuel pump screens, they looked clean and clear of debris.

#2 Took out the Y Connector and ran the motor off one 12 gallon tank. (instead of a Y Connector off to each tank, I look the Y off and put the female adapter in that hose and plug the male into that)

#3 I took out the fuel demand valve, I could here some sort of air noise whenever I primed the engine out of that thing.

#4 I ran one can of Seafoam through the engine, I constanly squirted for 3 minuates, than squirted alot of 15 seconds than shut it off, let it sit for 5 - 10 minuates and crancked it back over.


The results were I was able to idle smoothly at 1250 RPM instead of bouncing between 1500 than back to 2500. I think this may have helped, we will just have to see on the lake tommorrow. Do you think that sucking fuel out of two tanks would be much harder than out of one? I think this may have been the problem at hand.
 

Sea Rider

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Sep 20, 2008
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If with siamese fuel tanks hooked to a V connector. Try : (1) shut the air vent on one tank while the other tank vent remains open, when OB starts to starve for fuel, open the air vent which was closed and close the air vent on the near empty tank.

Will need to prime both tanks at same time with both air vents open before (1) so the second one follows with fuel on the line while the first is being shut. If not will need to prime second tank when the first in use is depleted. Check if this crazy procedure works out LOL !!

Use sometimes dual tanks, but are hooked individually with same short line, when OB starts to miss disconnect the one in use and connect the other one ASAP. Happen to have both fuel tanks at hand reach.

Happy Boating
 

Chrisravosa36

Chief Petty Officer
Joined
Aug 16, 2015
Messages
622
If with siamese fuel tanks hooked to a V connector. Try : (1) shut the air vent on one tank while the other tank vent remains open, when OB starts to starve for fuel, open the air vent which was closed and close the air vent on the near empty tank.

Will need to prime both tanks at same time with both air vents open before (1) so the second one follows with fuel on the line while the first is being shut. If not will need to prime second tank when the first in use is depleted. Check if this crazy procedure works out LOL !!

Use sometimes dual tanks, but are hooked individually with same short line, when OB starts to miss disconnect the one in use and connect the other one ASAP. Happen to have both fuel tanks at hand reach.

Happy Boating


still havent been able to get to the lake...But two new fuel pumps came, I was an idiot and realized that I have one 2 in and out fuel pumps, and one pump has the in and out and one other line, so esentially I have a 2 prong and 3 prong pump. I took apart the old pump, used the bottom pring on the new pump, I tried converting it to a 3 prong. It started up the motor, but again I got a higher idle at around 1500RPM (not in gear) and it was coughing and sneezing a bitfor the first minuate, after that it would only happen once every 30 seconds. I had to shut it off, worried that I would break something. Im wondering if the fuel pump has to break in? or what. I was going to bring it to the lake today but this happened. Idea's?



 
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