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Author Topic:   Fuel Hose Primer Flat at WOT

marinfr posted 07-02-2007 06:14 PM ET (US)
I have a problem with my 2000 Mercury 90-HP two-stroke ELPTO. At WOT the primer bulb goes flat and the engine begings to starve for fuel. At times the engine regains the RPM, other times stalls. The engine will be able to be restared and brought back up to RPM but the primer bulb will eventually go flat again. I have replaced the primer bulb. It is installed before the water seperator on my 2000 Montauk 17. No change in solving the problem.
Any suggestions would be appreciated.
Thanks
flawton posted 07-02-2007 07:07 PM ET (US)
How is the fuel tank vented?
Dick E posted 07-02-2007 07:29 PM ET (US)
Check your connections. Make sure your gas line clips snap on good and there is no air leaks. Pull your tube that goes into the gas tank make sure the stem is not kinked and the screen is clean. Do you have one main tank or do you have a small 6 -gallon tank?
jimh posted 07-02-2007 08:00 PM ET (US)
If the primer bulb is collapsing, it is an indication of a restriction in the fuel flow which is upstream of the primer bulb.
marinfr posted 07-02-2007 08:23 PM ET (US)
Thanks for the replies, the tank is a Tempo 12 gallan portable installed under the RPS. Is it ok for the primer ball to be upstream of the water seperator?
I will check for retrictions at the tank. The tank is vented through the filler cap. I have removed the cap completely and the problem still persists.
Dick E posted 07-02-2007 09:59 PM ET (US)
See a good reference article on primers:
http://continuouswave.com/whaler/reference/primer.html
marinfr posted 07-03-2007 07:36 AM ET (US)
Thanks for the link I did see this on the forum. Based on the article should I re-locate the bulb to a position downstream on the water seperator?
newt posted 07-03-2007 07:43 AM ET (US)
Yes, primer bulb should be close to the engine. Another culprit could be your fuel filter on the separator is clogged up. Either replace the filter or bypass it to see if it is the problem.
Tom W Clark posted 07-03-2007 08:53 AM ET (US)
This cannot be that difficult to troubleshoot. If the bulb is collapsing and it is upstream of the filter/separator, then the filter/separator is not the problem.
If the bulb collapses even when the fuel tank cap is removed we know the problem is not caused by a vacuum in the fuel tank.
That only leaves a restriction in the fuel line between the bulb and the tank or the bulb itself as the possible source of trouble.
I suggest you make sure you do not have the bulb mounted backwards for starters. If nothing else can be found, then presume the bulb is defective. Replace with an OE primer bulb, not those notoriously finicky Tempo brand primer bulbs.
Also pull the fuel hose out of the tunnel so you can verify you do not have a kink in it.
While there may be something to be said for having the primer bulb down stream of the filter/separator, my personal experience indicates it doesn't make any practical difference in a small boat.
Tom W Clark posted 07-03-2007 08:54 AM ET (US)
...and of course the fuel pickup in the tank is another source of restriction. Check it for debris.
jimh posted 07-03-2007 03:06 PM ET (US)
The only special requirement about the location of the fuel filter and water separator is that it should be located on the suction side of the system (or at least this is clearly spelled out for RACOR filters, perhaps not so for all other brands).
With regard to the location of the primer bulb and the filter and separator, the only reasonable differences I can see are these:
--the primer bulb ought to be downstream of the filter in order that operation of the primer bulb creates suction on the filter, not pressure;
--the primer bulb would benefit by being downstream of the filter in that the filter might remove debris which could clog the primer bulb.
On the basis of that reasoning, the primer bulb ought to be downstream of the filter and separator. However, all that said, I don't think it makes a great deal of difference. In actual fact, I have a primer bulb located upstream of my RACOR filter, and I have seen many installations rigged that way.
marinfr posted 07-05-2007 07:12 AM ET (US)
Thanks to everyone for the great advice. Looks like I resolved the problem. This is after swapping out the [primer bulb] first.
At the end of last season, I had a mechanic do some work on my carburetors and while working on the boat he recommended that I change out my [sight] glass and pickup tube assembly on my tank. What appears to have been happening is that the new pick up tube was left too long, where the end of it was actually sitting on the bottom of the tank. At times I suspect that the vacuum created a suction cup to the bottom of the tank.
I cut back the tube and the problem seems to be gone.
Thanks again, as I found this quickly only becuase I focused on the problem before the [primer bulb] as suggested.
Buckda posted 07-09-2007 05:08 PM ET (US)
Just a note: with a shorter pickup tube, you may have [reduced] how many usable gallons are in the tank capacity. I suggest caution when boating with a near empty tank until you get an idea for how much usable capacity was lost.
Dave

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Author	Topic: Fuel Hose Primer Flat at WOT
marinfr	posted 07-02-2007 06:14 PM ET (US) I have a problem with my 2000 Mercury 90-HP two-stroke ELPTO. At WOT the primer bulb goes flat and the engine begings to starve for fuel. At times the engine regains the RPM, other times stalls. The engine will be able to be restared and brought back up to RPM but the primer bulb will eventually go flat again. I have replaced the primer bulb. It is installed before the water seperator on my 2000 Montauk 17. No change in solving the problem. Any suggestions would be appreciated. Thanks
flawton	posted 07-02-2007 07:07 PM ET (US) How is the fuel tank vented?
Dick E	posted 07-02-2007 07:29 PM ET (US) Check your connections. Make sure your gas line clips snap on good and there is no air leaks. Pull your tube that goes into the gas tank make sure the stem is not kinked and the screen is clean. Do you have one main tank or do you have a small 6 -gallon tank?
jimh	posted 07-02-2007 08:00 PM ET (US) If the primer bulb is collapsing, it is an indication of a restriction in the fuel flow which is upstream of the primer bulb.
marinfr	posted 07-02-2007 08:23 PM ET (US) Thanks for the replies, the tank is a Tempo 12 gallan portable installed under the RPS. Is it ok for the primer ball to be upstream of the water seperator? I will check for retrictions at the tank. The tank is vented through the filler cap. I have removed the cap completely and the problem still persists.
Dick E	posted 07-02-2007 09:59 PM ET (US) See a good reference article on primers: http://continuouswave.com/whaler/reference/primer.html
marinfr	posted 07-03-2007 07:36 AM ET (US) Thanks for the link I did see this on the forum. Based on the article should I re-locate the bulb to a position downstream on the water seperator?
newt	posted 07-03-2007 07:43 AM ET (US) Yes, primer bulb should be close to the engine. Another culprit could be your fuel filter on the separator is clogged up. Either replace the filter or bypass it to see if it is the problem.
Tom W Clark	posted 07-03-2007 08:53 AM ET (US) This cannot be that difficult to troubleshoot. If the bulb is collapsing and it is upstream of the filter/separator, then the filter/separator is not the problem. If the bulb collapses even when the fuel tank cap is removed we know the problem is not caused by a vacuum in the fuel tank. That only leaves a restriction in the fuel line between the bulb and the tank or the bulb itself as the possible source of trouble. I suggest you make sure you do not have the bulb mounted backwards for starters. If nothing else can be found, then presume the bulb is defective. Replace with an OE primer bulb, not those notoriously finicky Tempo brand primer bulbs. Also pull the fuel hose out of the tunnel so you can verify you do not have a kink in it. While there may be something to be said for having the primer bulb down stream of the filter/separator, my personal experience indicates it doesn't make any practical difference in a small boat.
Tom W Clark	posted 07-03-2007 08:54 AM ET (US) ...and of course the fuel pickup in the tank is another source of restriction. Check it for debris.
jimh	posted 07-03-2007 03:06 PM ET (US) The only special requirement about the location of the fuel filter and water separator is that it should be located on the suction side of the system (or at least this is clearly spelled out for RACOR filters, perhaps not so for all other brands). With regard to the location of the primer bulb and the filter and separator, the only reasonable differences I can see are these: --the primer bulb ought to be downstream of the filter in order that operation of the primer bulb creates suction on the filter, not pressure; --the primer bulb would benefit by being downstream of the filter in that the filter might remove debris which could clog the primer bulb. On the basis of that reasoning, the primer bulb ought to be downstream of the filter and separator. However, all that said, I don't think it makes a great deal of difference. In actual fact, I have a primer bulb located upstream of my RACOR filter, and I have seen many installations rigged that way.
marinfr	posted 07-05-2007 07:12 AM ET (US) Thanks to everyone for the great advice. Looks like I resolved the problem. This is after swapping out the [primer bulb] first. At the end of last season, I had a mechanic do some work on my carburetors and while working on the boat he recommended that I change out my [sight] glass and pickup tube assembly on my tank. What appears to have been happening is that the new pick up tube was left too long, where the end of it was actually sitting on the bottom of the tank. At times I suspect that the vacuum created a suction cup to the bottom of the tank. I cut back the tube and the problem seems to be gone. Thanks again, as I found this quickly only becuase I focused on the problem before the [primer bulb] as suggested.
Buckda	posted 07-09-2007 05:08 PM ET (US) Just a note: with a shorter pickup tube, you may have [reduced] how many usable gallons are in the tank capacity. I suggest caution when boating with a near empty tank until you get an idea for how much usable capacity was lost. Dave