which fuel pump kit? '78 70hp :edit: fuel pump kit didn't fix it

[superwooter]

iboats web store list two fuel pump kits with the range of serial numbers that mine falls under. i called the help line, the customer service guy called sierra (manufacturer of both different fuel pump kit part numbers), and the end result was that there were two different fuel pump styles for that serial number range and the only way to tell is to try it.
i'm not really into that kind of wasteful experimentation (even though they're like 4 bucks) so i thought i'd see if you guys had any idea.
here's my info:
serial number: 4827765
year: 1978
model: 700 thunderbolt 3 cyl.
and here's links to the two possible fuel pump kits....
http://www.iboats.com/mall/partfind...gd_poid=112438&gd_row=35&**********=709353509

http://www.iboats.com/mall/partfind...gd_poid=242377&gd_row=36&**********=709353509

call it a hunch, but i get the feeling that it is gonna be the first link. but i'd like to have more than a hunch before ordering it.

any ideas?

thanks,
superwooter

 

[ajgraz]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

My 1979 70hp takes the one in your first link, the kinda triangular one.

You might consider kit 21-13424A1 from Quicksilver, which also contains new check valves. Costs more, but is a complete fix. When my pump stopped working, it was one of the check valves that was bad, not the diaphragm.

 

[superwooter]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

I'll take a look at it. mine is still working at the moment, but i am in the process of totally replacing/repairing my fuel system for good measure and that is about the only thing left to do.
is yours the 3 cylinder model? mine is, but i understand that a 4 cylinder model was made as well and i thought that might be what the difference is in the parts since iboats doesn't separate the two different engines on their parts list.

 

[ajgraz]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

3cyl. You and I have the same motor, just a model year apart.

If you are doing a "preventive maintenance" fuel system overhaul, then do get the kit with new check valves.

 

[superwooter]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

aj,
i WAS just going to replace it as preventative maintenance! i ended up not getting anything for the fuel pump because i wanted to get the quicksilver part you mentioned but didn't want to spend 25 bucks right then. well, i took it to the lake this afternoon for the first time after rebuilding/cleaning the carbs. it idled beautifully like never before in the 9 months i've had this old boat. i hammered on the throttle and the hole shot was like i've never experienced. but then after it planed off, it wouldn't go over 4000 rpm and it was sort of pulsating. after making sure the vents on my gas tanks were opened, we tried pumping the bulb. bingo! it surged up to 5000 rpm and as long as we kept pumping it, it kept the rpm's at WOT.

correct me if i'm wrong, but doesn't that mean my fuel pump isn't pulling the fuel? i'm hoping you guys will point me in the right direction as soon as possible. my cousin is planning on taking the boat fishing this weekend.

also aj, can you tell me where you got your quicksilver fuel pump kit? i googled the part number and found one website that sold it, but i'd much rather take your experienced word for it.

thanks,
superwooter

 

[RaScLeS]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

if you got that motor to idle and hit 5000rpm while priming the bulb its def. the fuel pump. lucky you, cause mine did that and the fuel ball did nothing

 

[ajgraz]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

Sounds like fuel pump is a definite suspect there.

Search 21-13424A1 on EBAY, the full kit with diaphragm and check valves are going for $18-$21 or so shipped.

 

[Faztbullet]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

It the first link you have posted (OEM#55278A4)

 

[ajgraz]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

It the first link you have posted (OEM#55278A4)

That Sierra kit (and the p/n you posted) is only the diaphragm and check valve seals. The only way to get new check valves also is the Quicksilver kit.

 

[superwooter]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

aj,
can you take a look at this link and verify for me that this is what i need? and to be clear, this kit does have the diaphram too, right?
http://cgi.ebay.com/ebaymotors/Merc...0828614QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

thanks,
superwooter

 

[Faztbullet]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

Just the check valves are OEM part # 21-30430 ....

 

[ajgraz]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

Just the check valves are OEM part # 21-30430 ....

So they are, I've looked for those before without success, thanks.

superwooter, yes that link on EBAY is the Quicksliver kit I've been talking about. Thanks to the p/n posted above you could probably put together your own kit for a few bux less, but that Quicksilver kit's got it all: diaphragm, gaskets, check valves, check valve seals, plus new check valve holder assembly and screw.

 

[superwooter]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

well it appears that the new fuel pump/check valve kit did not fix the problem. let me give a few more details to help with diagnosing the problem.

i mentioned that i just rebuilt/cleaned the carbs this past weekend. the previous time i had the carbs rebuild (about 8 months ago), my boat mechanic buddy that did the job set the adjustment screws on the carbs to 3 full turns out. factory setting is 2 full turns out. i mentioned this in another thread here on iboats and was told that that was an improper way to adjust the idle to keep it running at idle speed. but since the motor was working, i didn't want to go back in a mess with it.
well when we rebuilt the carbs this past weekend, i remembered all of that, so we set those adjustment screws back to 2 full turns out. it idles better than ever before so i don't even know if that adjustment has had any affect on why it would be bogging at top end.
one other possibility i can think of is that the thin metal tab that the carb floats rest on got bent during our disassembly of one of the carbs. we just bent it back and didn't give it a second thought.
the only other thought i have is that maybe during cleaning it this time, we might have dislodged some crud or trash or whatever that might now be blocking the high speed jets in the carbs.
all that being said, it does still accelerate on up to 5000rpm when the fuel bulb is squeezed.
so what kind of mess have i gotten myself into now? could a bad fuel line between the carb and the fuel pump cause this problem maybe? i don't see any leaky fuel though.
thanks,
superwooter

 

[ajgraz]

Re: which fuel pump kit? '78 70hp

Re: which fuel pump kit? '78 70hp

How old is your squeeze bulb? Could be a bad check valve in the bulb.

Also, when did you last check the fuel filter?

Finally, do you know if anyone ever removed the filter screens from the carb bowl feeds? According to the SELOC manual, those should be removed because they tend to get gunked.

 

[superwooter]

Re: which fuel pump kit? '78 70hp :edit: fuel pump kit didn't fix it

i have replaced everything fuel related outside of the engine from tanks to hose to filter to bulb to connectors all within 4 months ago.

 

[ajgraz]

Re: which fuel pump kit? '78 70hp :edit: fuel pump kit didn't fix it

I was editing my prev post to add the carb bowl screens when you replied, don't know if you saw that.

One other possibility...cracked fuel pick-up tube in the fuel tank (i.e., sucking air)?

 

[superwooter]

Re: which fuel pump kit? '78 70hp :edit: fuel pump kit didn't fix it

i think we can rule out the gas tanks. both are brand new and both act the same.
gonna replace the filter again for good measure.
i don't know about the screen you mentioned. is that something inside each carb?

 

[superwooter]

Re: which fuel pump kit? '78 70hp :edit: fuel pump kit didn't fix it

update:
my cousin who is using the boat today just let me know that now even pumping the bulb will not help the motor to accelerate. i'm starting to think something was possibly done wrong last weekend when we disassembled the carbs and cleaned them.
does anybody know any common mishaps in that department?
thanks,
superwooter

 

[CharlieB]

Re: which fuel pump kit? '78 70hp :edit: fuel pump kit didn't fix it

When you replaced the fuel lines, did you replace the fuel ine FITTING to the motor? With a FACTORY fitting?

Aftermarket often have a bad habit of allowing air to suck IN past the O-ring seal.

 

[BassnKY]

Re: which fuel pump kit? '78 70hp :edit: fuel pump kit didn't fix it

If the engine will not draw fuel at WOT, it usually boils down to 3 areas.
1. sucking air.
2. bad fuel pump
3. gunk clogging the carbs.

If you rebuilt the fuel pump, replaced the fuel tanks and lines, and rebuilt the carbs, I would start with the easiest first.

The fuel tanks bring up a question. are the fittings on the tank plastic? I have had the fitting, where you screw in the line crack on the bottom side and could not see it until I took it apart. Also, are the connections on the fuel line plastic?

I have been told by people that the plastic quick connectors are better. To be polite, I replaced all of mine with metals ones after several headaches.

Just a few thoughts. GOOD LUCK!!!