outboard problems

[tyke99]

h all, new to this forum so all advice is welcome, i have a yamaha 9.9 high thrust 4 stroke, the two problems are loosing revs at medium to high throttle, engine dosnt actually cut out but almost till i pull back on lever and then drives great, other problem is stalling when slowing down to moor up or enter lock, pretty dangerous with other boats around, mechanic has give engine a total strip down, had salt build up, new exhaust, gaskets ect, engine service, iv replaced primer bulb and hose connectors, new tank, new fuel, carb cleaned and still symptons persist, well after alot of money spent, still frustrated with season just round the corner, any help please, thanks

[Ianfs]

Ed .......your question!

[tyke99]

already stated!

[Ianfs]

Hi tyke, welcome to the forum.

Ed .......your question!

already stated!

No no no! But can I understand what you thought.

We have a moderator called Ed who is a wiz with outboards and maybe Gazjen as well as a few others too, but hence me saying Ed....your question!

[Nick]

First things to check are the carb settings, not just cleaning it, but checking it's adjusted correctly, the carb linkage, throttle cables (for the stalling at idle), fuel contamination (or old fuel) and the powerpack (or whatever Yamaha use for controlling spark). I had a failing powerpack on a Merc that caused the engine to bog down at high revs and stall at low and it was a simple fix. No idea what Yamaha use, but there must be something similar!

Nick

[_Ed_]

loosing revs at medium to high throttle, engine dosn't actually cut out but almost till i pull back on lever and then drives great

Fuel starvation. Not anything to do with jets, that would be immediate. So flow of fuel into engine, check pump, check supply feed, fuel shut off valve. If possible put a clean supply of fuel from a tank straight to the carb.

other problem is stalling when slowing down

possibly related to the above, check the above first with an entirely separate fuel supply to the carb and go from there.

[tyke99]

hi all, thanks for your replys, just an update, i took boat out on canal today and totally conked out, middle of canal, my mrs using paddle trying to get to towpath, engine was worse than ever, the first half hour she drove great until first lock and stalled, went through lock and again drove great for about another half hour then suddenly cut out completely, started straight away but when moving forward with lever only slightly, then cut out again, engine always started up straight away but wouldnt drive, soon as moved lever forwsrd it cut out, anyway finally creeped back to moorings and gave engine a while before starting her up again and stalled everytime after about ten seconds

[tyke99]

pressed submit then by mistake, to your previous advice, firstly im only a novice boater, so how do i take a fuel line straight to carb? And is that to rule out if fuel pump isnt working propely, the fuel is alwas fresh, not sure what a fuelshut off valve is, the mechanic advised me to raise the tank to engine which i did today to test fuel pump was working, have your heard of doing that, thanks al

[_Ed_]

Hes just trying to do the same thing really as I've suggested. Unfortunately its a bit difficult to explain, and with petrol great care must be taken. If you remove the cover, you should be able to follow the fuel pipe from the tank to the carb on the engine. You then need to connect a pipe (ideally via a small inline filter) to the carb directly and prime fuel into it. You will need to have the tank above the engine for this to work.

[Ianfs]

I don't suppose there is any possibility that you haven't released the vent on the fuel tank or are they self venting these days?