Outboard stalling when warm - any suggested solutions?

[nexus180]

Hi - this is my first post and I am a complete novice when it comes to boats/outboards, so please forgive any silly/obvious mistakes! I have a Tohatsu 3.5HP 4 stroke outboard (2007) that I bought used but in v good condition/ regularly serviced. Initially it had a problem idling without stalling, but I seem to have fixed that by changing the spark plug (and tweaking the idle screw). I've now come across a new problem in that the engine sometimes stalls when it is fully warmed up. It usually happens after I have had the engine at full throttle for 15-20mins+ and without me adjusting the throttle the engine starts to "buck" (if you know what I mean - the revs suddenly start to go swiftly from one extreme to the other), which it does a few times before stalling. When it does this it is usually more difficult than usual to get the engine re-started again. Any ideas what it could be? The only suggestion I have had is to run "Quickleen" through it to clean the carb out?

Many thanks for any help.

 

[dingdongs]

remove carb strip and blow jets out.put back together and put mixture screw back to its original setting.

 

[VicS]

Also check fuel flowto carb. (There is often a small filter hidden in the tank outlet or the fuel cock which can become blocked)

Tank vent?

Check if its overheating.

Even consider that the new plug could be defective


When you say tweaked the idle screw do you mean the idle speed or mixture?

 

[kashurst]

+1 on the carb, plus go through all the electrical connections, take the ignition coils off and check for corrosion underneath. Clean all the contact surfaces with emery cloth and stick it back together.

 

[nexus180]

Thanks for the replies - will check out the carb; I did notice when I changed the spark plug that the old one looked very black - could that suggest the carb needs cleaning? I've seen some people talk about the "Quickleen" additive for cleaning the carb out - or is is better to take it apart?

VicS - I turned the small screw underneath the petrol tank about a half turn, which I believe changes the idle speed ie it seems to have increased the revs when idling v v slightly