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Help with Mariner 30HP problem

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purplewg

Member
So I bought an old 14 ft Jon Boat with a 30HP Mariner. Went through and replaced all the wiring running to the motor, lights, bilge, and even the trailer. They were all sad.

Of course the guy said it runs like a top. lol I test it on water ears and it starts and runs. Me and a buddy take it to a lake with his boat as backup. We go 3-4 miles and it runs but not at WOT. We fish a little and start to head back and I make it about 75 yards in slow zone and it just shuts off. He has to tow me back. I get it home and don't like the smell of the fuel. I changed the fuel filter and replenished with fresh high octane and Star Tron additive. The next day we go out again and it runs ok but still no WOT. Again after troll fishing I start and run it about 75 yards slow and it shuts off and won't start. We drag it home and I remove the carb. It was super clean inside but the shut off valve/jet for the float had a piece of rubber stuck in it. Cleaned all the jets and emulsion tubes and put back together. Today we go test again and it runs WOT great. We fish a bit and it brings me back to the dock. I go get my trailer and it starts but shuts off when I put it in forward or reverse. Got it restarted only to shut off and not start at all.

I get it home and remove the cowling and notice no fuel in the filter. I go to the bulb and pump it and it fills right up. I leave the motor in the up position as I did on the trailer, go eat lunch, come back an 2 hours later and the filter is still full of fuel. It sounds like the primer bulb is leaking back to me but it is new as are the hoses from the tank to the engine. I think my other two failures coming back was no fuel. Just enough in the filter to idle 75 yards. lol

What do you guys think? Another primer bulb or something else? Sorry about the book but wanted you to have all the info.
 
Could be a weak, or partially plugged fuel pump....what year you think it is? If it had rotten fuel in it, possibly ethanol, the diaphragm in the fuel pump could be injured. Good story....you had me right there in the boat....and without the cussin' and swearin'.
 
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timguy said:
Could be a weak, or partially plugged fuel pump....what year you think it is? If it had rotten fuel in it, possibly ethanol, the diaphragm in the fuel pump could be injured. Good story....you had me right there in the boat....and without the cussin' and swearin'.
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I am told it is a 1983. I checked compression on it and both cylinders were 120PSI. The fuel didn't smell rotten just didn't smell fresh to me so I changed it to fresh. Anything I can do to check the fuel pump other than to remove it and inspect? Thanks for the reply.
 
Try to raise the fuel tank level with the motor and then the fuel pump would not have to work as hard. If symptoms go away then you can suspect a weak fuel pump, not able to "lift" the fuel.
 
timguy said:
Try to raise the fuel tank level with the motor and then the fuel pump would not have to work as hard. If symptoms go away then you can suspect a weak fuel pump, not able to "lift" the fuel.
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Thanks, I took test flight #4 this morning. Ran good across the lake. Got into to a creek and fished for about 2 hours on the trolling motor. It started right up but stalled when I put it in gear. Played with it a bit and it started. Started the 3 miles out of the creek and it stalled again after about 100 yards. I went back the primer bulb was slack. Pumped it up and ran maybe 1/4 mile and it quit. I went to the primer bulb again and it was slack. Pumped it up and it took me out of the creek and 2 miles across the lake. I think I am gonna change the primer bulb and the fuel pump at the same time. lol
 
Not a bad idea. It's probably the fuel pump, but primer bulbs are poor quality these days too....they don't last long. We are in the age of "synthetic rubber". The primer bulb on my 1965 Evinrude Fisherman 6hp. is original equipment with over 3000 hours on it. Still works perfectly and looks like new....it's made of real latex rubber, that's why. That very same primer bulb is right behind "Farmer", in my avatar which was taken in about 1977. You might have trouble too with the "laminated" fuel line which can break down internally, partially blocking fuel flow. I recommend......if in fact you really DO have the grey colored "laminated" type hose.....that you replace it with 5/16 or 3/8" reinforced rubber gas hose from your auto parts retailer.....or purchased however you wish.
 

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timguy said:
Not a bad idea. It's probably the fuel pump, but primer bulbs are poor quality these days too....they don't last long. We are in the age of "synthetic rubber". The primer bulb on my 1965 Evinrude Fisherman 6hp. is original equipment with over 3000 hours on it. Still works perfectly and looks like new....it's made of real latex rubber, that's why. That very same primer bulb is right behind "Farmer", in my avatar which was taken in about 1977. You might have trouble too with the "laminated" fuel line which can break down internally, partially blocking fuel flow. I recommend......if in fact you really DO have the grey colored "laminated" type hose.....that you replace it with 5/16 or 3/8" reinforced rubber gas hose from your auto parts retailer.....or purchased however you wish.
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The fuel line looked new to me but when I looked up the SAE # it did not say Marine or Ethanol friendly so I ordered black "Marine and Ethanol Friendly line". I pulled the fuel pump yesterday. It had been changed before. I don't normally do this but.... I know there are two check valves inside so I sucked or blew on both the inlet and outlet. I could pull or push air with not much problem. Did I mention it leaves a bad taste in your mouth. lol I should get the new pump tomorrow and off for flight test #5 the next day. Wish me luck.
 
Ha! Good taste, eh? The check valves may work okay within the pump, but the diaphragm may be damaged.
 
Ok, so I got the fuel pump and new primer bulb and hoses installed. I also had to replace the fuel line between the pump and the carb. Wasn't leaking before but was after the pump install. Fired her up and noticed quite a bit of air in the line going to the carb. I figured it was air in the lines. Then I noticed the fuel filter was only about 1/3 full sitting there idling. Brought the RPM's up a bit and the filter still was not full. I went around and grabbed the primer bulb and pressed it a couple times and it went flat but did fill the filter. The motor kept humming, the air in the carb line went to tiny bubbles. Let it run on the water ears for maybe 5 minutes and shut it down. The primer bulb remained flat. I took the hose loose between the bulb and the tank and it still stayed flat. I massaged the bulb a bit and it slowly went back to full size. The old bulb never did this. I have never had one stay flat after removing one end. Ideas? Thanks
 
Could there be a problem with the suction tube coming from the bottom of the fuel tank, up to the fixture? Is it an aftermarket plastic tank? Some of them are pretty problematic.
 
timguy said:
Could there be a problem with the suction tube coming from the bottom of the fuel tank, up to the fixture? Is it an aftermarket plastic tank? Some of them are pretty problematic.
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No, I pulled the whole fitting out with the tube. All was clean and open. Thanks
 
I have seen an air leak where the plastic tube is pushed into the fixture....some aftermarket tanks are pretty poorly engineered and using bad plastics.
 
timguy said:
I have seen an air leak where the plastic tube is pushed into the fixture....some aftermarket tanks are pretty poorly engineered and using bad plastics.
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Well, the fuel filter has held full for a couple days now. Weather has been too bad to try and get out for another test.
 
The filter will hold because there is a check valve in the squeeze bulb and of course upstream too, in the fuel pump. If the tank is leaking, as I mentioned, it will allow air into the system.
 
Finally had a chance to take another test ride. It ran fine except when I let is sit for a bit. Seems to be cold natured and I have to hit the choke for each start. At least it did not shut off on me at low speeds which makes getting it on the trailer a lot easier. lol
 
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