Why does my engine stall?

[rburlington]

Okay, transom works.  Now the engine does not.  It is a 1986 Yamaha 220 HP with oil injection and 300 hours.  Was fully tuned at 235 hours.
Full story:  Got bad gas with water and sorted that out.  Had hose leaks and pump bulbs that would not work.  Got that sorted out.
Finally, got 5 gallons of gas in auxillary tank and took her out.  Runs good even at hight speed; but at high speed (4,000 rpm and up) she runs about 1 minute and then dies as if it ran out of fuel.  It does not do this at lower RPMs and speeds.  My initiall theory is that the 13 gallon tank on the deck tips as the bow rises and the gas runs to the back starving it for fuel.  5 gallons only fills it 1/3 full.  I will test this as soon as possible, but it was not possible yesterday and could not get gas out of the main tank (which is full) to see if the same thing happens from there (due to line and bulb problems).

Assuming I rule out low fuel level in the auxillary tank, what else could be wrong?  What else should I look at?  There is no miss or electric problem, just feels like it runs out of gas.
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[jdupree]

When it starts to stall out, is the primer bulb "limp" or tight?   If it not staying tight you have a fuel delivery problem meaning sucking air or fuel pump.

[rburlington]

John, the bulb is limp and therefore it is getting air.  After I check whether or not this is due to the gas running away from the intake due to being low in the auxillary tank and get the main tank functioning, I would guess by your reply that I should change out the fuel pump(s) [this model may have two pumps] next.
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[jdupree]

So you have hooked a portable tank up to the motor and it does the same thing   If it does, that would narrow it down to the motor.  I would just double check all of the gas line fittings on the motor and if they are ok I would lean toward the fuel pump.  If you have a manual to the motor, I want to say it will tell you how to test the pump.

[rburlington]

I have been too busy to read or post lately, but finally have gotten a chance.

Here's the outcome on my engine stalling problem:  There was so little fuel in the auxillary tank that when I got on a plane the fuel was running away from the intake and the engine quit.  On the main tank, the engine would not run at all because there was an air leak at the connection to the tank.  Once the main tank connection was sealed shut and the engine had a source of fuel, there was no problem.

[RebelYell]

Thought to add two cents and some observations....

I had the same problem on my 1990 Osprey 200. I purchased the boat from a guy in Pompano Beach in March.

After checking fuel pump, bulb, tank check valve, etc I found the problem.

Sometime, in the dark and distant past, a jackleg boat mechanic somewhere in South Florida thought it would be a good idea to get some "return business" from the previous owner.

So, he took some black cable ties and tightened them down on the fuel vent line about 18-20" from the thru-hull vent and choked off the flow of air. The tank wouldn't vent properly when fuel was withdrawn and would vapor lock. I would stall and die off, only to look back and see my bulb crushed flat from the vaccum. It would only occur after a few minutes of running at WOT; when I cracked the fuel/water seperator cannister it would equalize the vaccum and go back to running fine.

Learned my lesson.

When buying an older boat you need to go through EVERYTHING with an attention to detail.

I also had to replace every one of the bleeder lines on the Mariner 150 that came originally with the boat; as some were paper thin and a couple of 'em ruptured after I bought the boat. The service manual indicated that they weren't even routed properly. I have replaced every inch of fuel carrying line from the tank to the fuel and bleeder lines.


Be aware. Not all mechanics are honest. The previous owner probably had this problem for a long time and never got it "repaired" no matter how many $-times-$ he took it back to his "trusty" mechanic.



RebelYell.....Winter Haven, FL.

[JimCt]

Well put.  Agree 1000%.
As Reagan once said... trust, but verify!

[rburlington]

Excellent point.  You can't be too careful.

I try to figure things out by myself and with the help of my friends first.  In addition to that, I have certainly gotten a lot of very useful advice from people on this forum too.

So far, I have avoided mechanics and boat doctors.  One guy in particular in our area holds himself out as a doc for boats, but my only interaction with him was during the spring when he should have been very busy.  He was poking around on a small drain problem on a customer's boat; gave up on that when he found the boat covered; spent the next 40 minutes talking to me.  What's wrong with that picture?

Although I am not highly skilled, 20 years of living in Central Africa with little recourse when problems arise, helps.  There we used to say, "The local mechanics do not know and they do not care.  I only don't know."

I have had a good look at the whole system from carbs back to the fill spout and am happy to report that there are no restrictive ties or any other strange things!  Since fixing the main tank connection we have travel WOT for several miles at a time with no further problem.

Thanks for the inputs.
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