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Bogging and dying

E

ejbtech1

Regular Contributor
"Here I am again with another

"Here I am again with another ongoing issue with my engine. As some of you know I have an AQ120B that really did well last year. She developed a blow by issue, which turned out to be the carb dumping too much gas and diluted the oil. I retorqued the head, and replaced the solex side draft with one from e-bay.
I went through the carb, and all seems to be ok. It runs well in the driveway, but when on the water, she bogs down and dies. The longer she runs, the worse this issue becomes. I ended up pumping the throttle yesterday to get back to shore..........
Where should I start? Up until the blow-by issue last year, she ran awesome."
 
"Eric,

Again, blow-by is ca

"Eric,

Again, blow-by is caused by worn piston rings or cylinder walls. What compression are you getting in your engine? This is the first thing you have to find out."
 
"I call it blow by, but as I s

"I call it blow by, but as I said earlier, it was gasoline washing down the cylinders. I have compression readings of 150 on all 4. It runs good on land, it is when I put the boat in the water that I have problems. I am leaning back toward a fuel related issue."
 
Is it possible that the electr

Is it possible that the electric fuel pump you swear by could be the problem? Have you tried to install a pressure gauge and monitor the fuel pressure?
 
"I just installed a new fuel p

"I just installed a new fuel pump, as mine from last year failed.....But that is possible.
You remember me well, huh?
I appreciate your advice......I did not try to take the gas cap loose yesterday.....maybe anti siphon?"
 
"A pressure gauge between the

"A pressure gauge between the fuel pump and the carb will tell you if there is too much or not enough pressure (2-4 psi). Too little pressure could be blamed on the anti-syphon valve or a failing pump; too much pressure would indicate the wrong type of pump for the application.

Yes, I still remember our debate about electric versus mechanical fuel pumps. Without disregarding some of the advantages of electric fuel pumps, I still think that a mechanical fuel pump is the best way to go with your particular engine: it is specifically designed to work with it; it is not expensive; and it has a proven track record.

http://www.marineengine.com/parts/part_details.php?pnum=SIE18-7286&returntopage= sierra_marine/sierra00811.htm"
 
"I am using a 5.5-9 psi pump,

"I am using a 5.5-9 psi pump, found a better design than the last, also an inline regulator. (maybe that's gone bad,too?)
I have not tried a guage, but might implement that permanantly, now that you mention it.
What else could be the issue? This thing runs too good to be a mechanical engine-type issue."
 
"I think you should go one ste

"I think you should go one step at the time. I suggest that you first check the fuel pressure, then look into something else if that is not the problem."
 
"That's where I will start

"That's where I will start. I did notice that it looked as if the accelerator pump might be leaking.....That could also explain my dillemma too, huh?"
 
"Now that I have looked back t

"Now that I have looked back through old posts, I bet the accelerator pump is the biggest part of my problem........"
 
"If that was the case, then ho

"If that was the case, then how do you explain the issue of gasoline washing down the cylinders?"
 
"That was with the old carb...

"That was with the old carb.......It had been severely corroded with salt from the ocean.....
I now have a carb from a fresh water boat. And it apeared to work correctly, however, I did notice that the accelerator pump might be leaking.
I explain the gas washing down the cylinders with the old carb, because the oil was full of gas. That's why I changed carbs. And it ended up blowing by and out into the bilge from the hole in the valve cover.
Now I have no blow by or issues of that nature, just bogging and dying."
 
"Well, changing the diaphraghm

"Well, changing the diaphraghm in the accelerator pump is not complicated. But again, I would check the fuel pressure. Also, I hope that with so much gas in the crankcase in the past you did not have excessively low oil pressure and ended damaging rod bearings and the crankshaft."
 
"Me too....Thanks EL, I will r

"Me too....Thanks EL, I will repost my findings next weekend when I try a few other things....."
 
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