1957 Evinrude Lark 35hp " Fuel pump Issues"

[Squirrel42]

I have recently resurrected a 1957 35hp Evinrude lark. Carb rebuild, New points, Condensers, Spark plug leads, boots, springs. Complete over haul of lower gear case, with all new seals. I'm so ready for this to be done. Fired her up and she sounds great, than this BS!

Cannot get my engine to run with out constantly squeezing the fuel bulb from the tank.

I have the Sierra 18-7351 Fuel pump installed.

Drilled and tapped the recommended bypass port and installed pump with gasket over the correct drilled hole.

Installed it Upside down and Right side up, no change, still squeezing!

I have tried two fuel tanks and still the same problem.

I can pump it until its rock hard but after the engine runs for 30 seconds it eats all the fuel, revs high and dies.
Something is not pumping!

My best guess now is possible faulty pump?

I own a 15hp Evinrude 1973, Could i take the pump off it and do a test? I have a feeling the pump may be to small to test it!

Please help!

 

[Crosbyman]

do test with a new pump .......at idle the other pump should suffice to prove the point


do you or not....feel air pulsing out of your drilled hole in the side cover plate be

 

[Squirrel42]

SUCCESSSSS! It was a faulty pump! Can you freaking believe it?

I have my pump off my 1973 15hp on it and it's just chugging away in the yard. Now can i keep this pump on the 35hp or am i going to have fuel issues?

 

[Crosbyman]

well there are 2 answers yes and no ....:laugh:​


1- Yes .. keep it on and... try it at high speed for 5 minutes to see if you will starve out of fuel



2- No.. you can't use the smaller pump because it will not pump enough fuel at high speed.

and you now need a pump for your 15hp engine anyway ... may as well get a good one for the 35 instead or... fix your bad pump...check diaphragms for proper mounting.

 

[Squirrel42]

Well damn, I wonder what the hell could be wrong with this pump. I just don't see any reason it should not be working like the old 1973 pump.

Anyone one else ever had a new pump just not work?

 

[oldboat1]

poss. difference in mounting (air leak), hoses/clamps(?)

 

[F_R]

Probably a problem with one of the check valves. Could be a manufacturing defect or a hunk of crud got in it. Hard to say without taking it apart. You probably do not want to disturb it if you plan on returning it for warranty replacement. Otherwise it would be interesting to know what happened. I hope they didn't cheapen the construction, those are (were) good pumps.

 

[Crosbyman]

well if the problem is not external you need to open it up ad check out the diaphragm and/ or check valves if any

you did a good blow test (in to out only) so one must assume the check valves/diaphragms are ok

what is left... the mechanical operation of the main pumping diaphragm to suck and push fuel (pulse port blocked inside ?? air leaks ??? engine port not lining up with pump port ???)

 

[F_R]

If even one of the check valves work, it will pass the blow/suck test. Not a reliable test

 

[Crosbyman]

true...a false positive result.... but if the blow test does fail.... that ain't good !

 

[Squirrel42]

Unfortunately I read from another post to buy this pump Sierra 18-7351 for my 1957 35hp single line fuel conversion. It turns out this was the wrong pump and is for 9.9/15 HP 1993-2001. The guy later comments farther down the forum that he was incorrect and says that 18-7352 is the correct pump.

Sierra 18-7352 is for 35hp-55hp, So I'm out $50 and ordered a new pump with 2day delivery. I'll be back in business Saturday.

This was the recommended pump so i didn't do my research of course and that's my fault!

Thanks for all the help and i will post my end results, for now maybe go test out this smaller pump and put around waking the engine from it's 20 years sleep.

 

[F_R]

I disagree. You said you drilled the bypass cover and mounted the pump directly to the bypass cover, with a gasket between. If that is what you did, 18-7351 would be the preferred pump. It has a 3/16" outlet nipple, which is compatible with the filter or carburetor inlet nipple on your '57 motor. I believe 18-7352 has a 1/4" outlet nipple, so you are going to have to do some re-engineering on the hoses to make it fit. Aside from that issue, both will work on the motor. Either will pump enough fuel. And fuel pressure is determined by crankcase pressure in the motor, assuming it has enough flow capacity.

That stuff about it being for a 9.9/15 is because of the direction the hose nipples point. They point the correct direction to be a drop-in replacement for the mentioned motors, but you have to replace (or reroute) the hoses to use it on your '57. But you were going to replace them anyway, right?

 

[Squirrel42]

Either way I ordered the 18-7352 pump and it worked out great.
Not sure what was wrong with that pump.

Just happy I now have the fuel flowing and got the engine to run.

Now i have a stripped lower spark plug to deal with. Oh the joys of boating!