75HP Mercury no power!

[Pro-Duck]

So I have this motor on my 5. Duck, also a 40HP Tohatsu as a "emergency motor" After this problem occurred I cleaned the Carbs, replaced fuel lines and filters but occasionally still happens.
What it does: I leaf the harbor in Gansbaai and as i exit i accelerate, nothing happens, doesn't want to go!...then I struggle on like this and sometimes it pulls away and plain quickly. other Times it plains right away and we fly to the fishing spots,throwing out crayfish nets idle around the whole time, then we need to go back...nothing, almost as if the boat is pulling 10 tons. takes ages and the starts to accelerate....as I said I cleaned the Carbs, replaced fuel lines and plugs and filters but occasionally still happens.
it idles fine, i open throttle but nothing changes
any trouble shooting and help will be appreciated,.

Thanks

 

[Leon Brits]

Did you check the diaphragms?
Needle and seat not maybe messing around?

 

[IWyk]

Normally these symptoms will point to fuel supply issues.
Check also fuel lines and connections as well as fuel pump, sounds like it sucking air somewhere. Try the following. With the engine off and cover off so you can see what is going on, pump the primer ball as hard as possible and keep pressure on it, carefully follow the fuel line all the way to the fuel pump, check the fuel pump housing and then all the hoses to carbs. Any wet spot will show you where the problem is. When the engine is running you cannot see this as it will be sucking air in and not pushing fuel out.

Good luck

 

[Cam Mundy]

As mentioned it sounds like the engine is battling for fuel what sort of fuel tank are you using? make sure its venting properly.
Not to familiar with Mercury two stroke on the yamahas the heat sensors can be faulty making the motor go in and out of safe mode, on Yamahas its a thermostat plugged into the top of the block with a brown and a pink wire leading out unplug it and see what happens.

 

[Pro-Duck]

Thanks a lot, Its white plastic fuel tanks, i unscrew the caps always, so it can suck air into the tank. the pipe in the tank is cut into a V . I have been using this setup for 8 years.I will be back in Gansbaai in three weeks, I replaced all the fuel lines and filters, I will check the fuel connection where it goes in the cowling etc, and all the other suggestions. Thanks!!!

 

[TimJan]

Another thing you can do is when you are giving full throttle and the boat does not want to go let someone pump the primer ball if the boat takes off like a rocket you have a blockage somewhere. If the primer ball is pulled flat it means the blockage is between the ball and fuel tanks else it might be in your motor also check your needle and seed as just a little bit of dried oil can cause weeks of headache.

 

[MichaelK]

Pro duck it sounds very much like the problem i had with my old 2 stroke yammies. Because i wasnt fishing as regular as i wanted, the 2 stroke oil would seperate from the fuel and form a sludge at the bottom of my tanks. This sludge would then clog up the carbs everytime. I stopped storing my fuel and only filled up the morning we launched. Never had problems with my carbs again.

Ps: the bottom carb is inveriably the first carb to clog up. Be very careful when cleaning / unclogging your injectors.

 

[Jos101]

I had a similar problem on my Yammie 60hp CE.

Started with the obvious things and checked fuel line and replaced diaphragm but the problem persisted. Then had the carbs cleaned and the floats reset - when we tested the motor with the muffs it ran like a charm but as soon as it was under load the same problem.

It ended up being one of those plastic 'thingies' (think its called a clevis) which connects the rod on the advance/retard, being broken and accordingly not regulating the airflow properly. Replaced the broken dinges and reset the timing and all was well with Sally.

Hope this helps.