engine stalls at mid revs

tipidave1 · 19 May 2010, 21:40

Hi,
I have just been out in my 5m Searider with 75 Mariner 2 stroke. just fitted with a vengence SS prop

Fantastic!

It was serviced in Feb, and this was my first outing.Engine starts on the button and runs beautifully at low revs and full throttle

.

But at mid revs (around 20kt) it start to splutter and stall a bit

. A quick squeeze on the fuel bulb and it is ok for another few minutes. then same again. Any ideas? Blocked Jet? Definitely seems to be some kind of fuel starvation issue.

Could it be that the carbs have dried out since last service and left some residue behind? If that is the case, can I use a product to clean the carb whilst the engine is running? Any advice greatfully received.

Nos4r2 · 19 May 2010, 21:44

Check your fuel pump diaphragm for pinholes.

tipidave1 · 19 May 2010, 21:48

This was replaced about 50 hours ago. Wouldn't it not run at all revs? At full chat it runs great!

spartacus · 19 May 2010, 21:57

Is the fuel old? Definately worth putting in fresh fuel at the start of the season. Also check the fuel filter. If that's clear, check the fuel lines and the primingbulb/pump in particular. You can check the valve by blowing into the pump. I know it's obvious, but also check the fuel tank is properly vented.

Could be the fuel pump. If you disassemble to check the valve or diaphragm for cracks, distortion or perforation - you'll need a new gasket to rebuild.

Other than that - then my next port of call would be the carbs themselves - but as it was serviced in February, I'd check the other parts first.

tipidave1 · 19 May 2010, 22:09

Thanks for reply. I iwll try to be systematic and work my way through everything in order.

The tank vent was open.
The filter/ water seperator was replaced during service.
I carry two 25 l tanks each of which produced the same problem. They had approx 1/3 and 1/5 fuel that was 6 months old. Both tanks were topped up to full with fresh fuel.
The priming bulb did not go very firm upon squeezing... could this be a clue?

spartacus · 19 May 2010, 22:21

Quote:

Originally Posted by tipidave1

4. The priming bulb did not go very firm upon squeezing... could this be a clue?

Before you start the engine for the first time, on priming - the fuel bulb should become hard. If it's not - then I'd investigate further. Do you have a spare fuel bulb to compare?

tipidave1 · 19 May 2010, 22:29

o spare but looks like a good starting point. what is it harcreates the resistance to further fuel movement?

Nos4r2 · 19 May 2010, 22:58

Quote:

Originally Posted by tipidave1

o spare but looks like a good starting point. what is it harcreates the resistance to further fuel movement?

The float needles sealing when the floatbowls are full.

tipidave1 · 19 May 2010, 23:01

Thanks, I'll investigate over the next couple of days.

uncle al · 20 May 2010, 10:17

if the engine has sneezed it could be running lean at 2000rpm an burnt a hole in the fuel pump pulse hose or its connections if you want to ring me on 01869 326411 but not on fridays

9D280 · 20 May 2010, 12:25

Yeah, my old Suzi dod that. Upped the idle mix a bit to get it over the hump. I spent a day poking the choke to get it past 2K before I could adjust it..........