'00 250SX... Possibly a dumb question

[DennisG01]

(it's fuel injected - in case there were both carb and F.I. models available in '00)

OK, maybe it's a dumb question, but I would hate to not ask it just for fear of sounding stupid. I've tried searching, but to no avail...

So, this is my first "big" outboard. I'm very familiar with stern drives and inboards, but that experience does not help in this case. I've also had a few smaller OB's (50Hp and under) over the years, and that only makes things more confusing!

Question: How hard should the primer bulb get? With the small OB's the bulbs got nice and hard. With this one, I can squeeze and squeeze and it never gets as hard as I'm used to. I would "loosely" say it gets half hard/full of fuel - regardless of how much I squeeze it.

There's more to this story at my original thread http://www.yamahaoutboardparts.com/f...m-th23920.html but I thought it might be best to ask this specific question separately, just in case it has no bearing on my RPM issue.

Follow up question... Since this is a fuel injected motor, why do I need the bulb? Is it because the distance from the tank to the low pressure pumps is quite a long distance... along with the pumps being more "uphill" from the tank than a fuel pump in a stern drive would be?

[99yam40]

Primer bulb should get firm once everything is filled with fuel.
Sucking air or fuel leaking out is the only reasons I can think of that it will not firm up unless the check valves in bulb are bad.

Fuel pumps work well for pumping fuel, but not so good at pumping air.
Need to get fuel into the system for everything to work well

[TownsendsFJR1300]

Once the line is filled, you really don't need that bulb.

The only time I've EVER used it, is when replacing the transom fuel filter(and water separator). Even the Yamaha, under cowl filter will fill itself (if R&Red).

For just going out, I NEVER pump it, NEVER... And the engine can sit for a month, NO use, cranks right up, again, NO pumping...

I have found the cheaper named bulbs don't last as long as a genuine Yamaha bulb (3/8" bulb).

I have a spare on the boat, another in the garage for general work on other engines, etc..


For any fuel hose connections beyond the engine itself, I really like the old Evinrude plastic clamps,

http://www.ebay.com/itm/322654-OMC-J...-/361297788849

[99yam40]

Injected motors do not have the fuel open to air like the carbed motors so fuel does not evaporate easily so the system will stay full longer

But Running a fuel pump that uses the fuel itself for lubrication and cooling with air in it trying to get liquid fuel up to it is not a very good thing to do

[zenoahphobic]

With carb motors the fuel pump if squeezed excessively will force fuel past the needle and seat, and thus past the float and out of the vent or run down the throttle throat causing flooding.
That is why I only keep squeezing till it gets reasonably firm (not hard hard).
F.I. is a closed system, you may require more squeezing to fill up the volume required, otherwise what has already been said, either a leak or weak bulb.

[99yam40]

I have never had a motor that squeezing the primer bulb as hard as I could , would force fuel past the needle and seat once the float closed it off.
If it does there is a problem with the float or needle and seat

[zenoahphobic]

I have never had a motor that squeezing the primer bulb as hard as I could , would force fuel past the needle and seat once the float closed it off.
If it does there is a problem with the float or needle and seat

They have their limits. My 1984 115 did this from new, the carbies have been cleaned and rekitted. I just don't go overboard, stands to reason when you see the tiny rubber "top" on the end of the tiny pin attached to small tags on the floats.
On reflection in the early days I may have not placed the engine fully down (vertical!) before priming because I did not want the engine picking up sand from the bottom when starting.
I still follow the same ritual with my 175 but the boat is usually in deeper water when I start it. (many hand squeezes then firms up and stop)

[TownsendsFJR1300]

Running a fuel pump that uses the fuel itself for lubrication and cooling with air in it trying to get liquid fuel up to it is not a very good thing to do

Very good point.

My motorcycle has the HP pump in the fuel tank (FI'ed) and I won't run the fuel tank below 1/3 exactly for that reason.

She (da boat), will get a pump or two on initial start up from now on.. Thanks..

[zenoahphobic]

Air in electric fuel pump sure is not a good idea!
Air plus fuel plus commutater sparks equals boom! (Law of physics)

[oldcobia]

Getting primed

I use mine sometimes a few times a week to once a month. Depends on the mood. It doesn't matter, a few squeezes and it works great.

[TownsendsFJR1300]

Mine, in 8 years, has always started immediately W/O any squeezing.

[DennisG01]

OK, sounds like this "could be" a contributing factor to my (occasional) surging RPM issue - or at least not one to rule out. The problem is that the issue is so intermittent that it's hard to nail down what's wrong. Thank you for all the comments - although the engine will start without pumping the primer bulb, I've always done it because the only other times I've had a primer bulb are older, smaller engines. Maybe I didn't always need to do it with them, either?

But this is good information. To be honest, I kinda thought it should of gotten harder, but since the engine always started well (maybe, at the most, about 3 or 4 seconds of cranking if it's been sitting for a couple weeks) I didn't really think much about it.

And... I love those clamps, too. 2 zip ties can do the same thing if the nipple/barb is long enough (rotated 180* to each other), but I feel these are more secure... and of course reusable!

Am I correct... A low pressure fuel pump works because the pressure/vacuum created as the piston moves? I just took one (an old one) apart and it "appears" that is how it works. And, if I had a leaking LP pump (leaking into the air intake area of the engine), I suspect I would have more noticeable problems?

[boscoe99]

[TownsendsFJR1300]

And... I love those clamps, too. 2 zip ties can do the same thing if the nipple/barb is long enough (rotated 180* to each other), but I feel these are more secure... and of course reusable!

I like them best, BUT, (I think its Yamaha, who makes them), the inside, clasping end (if you would) has a "curve on the inside" edge for better sealing.

But like you said, not re-usable...


Any kind (ever so slight) of air leak near the bulb, transom filter, etc WILL cause issues. While on my neighbors boat(200 Yammy), the engine wouldn't run without constant priming the bulb to get us home. Turned out to be the flat rubber gasket on the transom mounted fuel filter split, just enough to suck air and disable the engine. I just kept a pumping till we got home..(keep it clean guys..).

And the Yamaha brand primer bulb MUCH more expensive that the Seachoice, etc, you feel and see how much better made it was. (around $20.00 as I recall)..

Priced like G0ld

[DennisG01]

Thanks Boscoe and Scott. I don't know how old the primer bulb is, and although it "feels/looks" to be in good shape, like mentioned above maybe it's failing on the inside. Easy enough to replace. I'll probably just grab a Merc bulb, but that's only because I work part time in the marine business so it's easy and cheap to get one that way.