View Full Version : 84S&S upgrade and fuel pump question

07-12-2006, 01:36 AM

I am another lurker who has finally decided to make a post. A friend and I bought an 84 S&S six months ago and with wives and family intolerant of on water issues, have been doing it up ever since. With assistance we have:

- repaired the platform mounts - the bolt through solution
- changed to electronic ignition
- replaced the starter and battery cables - after a nasty bilge water induced short
- built a trailer prop guard after more than one ding...
- changed the impellor - that was easy but we managed to screw it up. No damage done.
- changed fluids
- reupholstered
- removed the monkey bar - it was flexing the gunnals - we are planning a side bar and high pole fabrication
- cut and polished the gelcoat.
- put in perfect pass

Photo attached. The boat always ran ok, but now runs fantastically. We've learned an incredible amount from the posts you all have made. Its all quite amusing as well. Even though you dont know it much of the time, lurkers are using your knowledge to build and maintain great MC boats. Thanks.

My post is driven by a problem that I have searched quite hard for, but couldnt find. Twice now we have had a non-start due to no fuel reaching the carb:

- after the fuel tank was out. Fuel was blown through, and the engine subsequently ran perfectly
- last weekend after the boat had not been run for two months while the upholstry was done. We had no compressor so I took the fuel line off the carb and sucked until I got a mouthful. We dribbled some fuel into the carb and reconnected the line. The engine started and ran perfectly all afternoon. We also discovered at that time that the autochoke wasnt working - separate issue. Once fuel was at the carb, pumping the throttle results in a tidy fuel ejaculation into the barrels.

So it seems the mechanical fuel pump (age unknown) doesnt have the muscle to get fuel up to the carb if there is no fuel in the pump-to-carb line. This same thing is not uncommon in outboards - you use the bulb pump before you start. We have done no maintenance on fuel filters.

Replacement would seem sensible but here in New Zealand Mastercrafts and old marinised 351-Ws arent that common - no Skidim or Rambo marine etc. Chris at MastercraftNZ is a great help, but before I approach him to order/order from the states I thought I would check:

- Should we replace? We dont winterise and the boat gets pretty much year round use. If I have to taste petrol occasionally - no big deal. What about putting a bulb pump somewhere in the line for these odd occasions? That being said, the pump might be on its way out? Is it urgent?
- Is replacement with an electric fuel pump smart. Ive seen a post that suggested not to do this, but has anyone done it? I believe the fuel pump, mechanical or electric should be marinised. Again, maybe not so easy to find such a pump in NZ
- Can we maintain/repair the existing pump? Replace the diaphram (with an automobile version)?

Pulls always available at Whakamaru (http://en.wikipedia.org/wiki/Whakamaru) in NZ.



07-12-2006, 08:02 AM
Remove the fuel pump and open it up. you will see 2 diaphrams, one may have came out of its seat. If so press it back into its seat.

I had simular problem and I did the above and it lasted 2 seasons before it failed again. At least worth a try. But in the long run you will need a new pump.

Sorry, I cant tell you if it matchs a standard auto one or not, I bought mine off of skidim.com.

Oh yes, nice boat!

07-12-2006, 06:09 PM
Replaced mine recently. The early symptoms were much like yours, although I didn't recognize it at the time as a fuel pump issue. It wasn't long before I had gas in the sight tube and then I knew for sure it was the pump. I think what happened is that it wouldn't prime itself because the diaphram was failing. When it had air on the carb side it wouldn't pull gas. Once it was manually primed all the way to the carb it would seal off enough to pump and run the boat but then it started leaking into the sight tube. Replaced it myself. There's a thread on here about it under "fuel pump install". It's a relatively inexpensive part. I think you do need a marine specific part though.