Tohatsu 30hp 2 Stoke Boggs down on acceleration

[Ah Me Ting]

to bloody windy, this w/end

Yep. I mowed the lawns.

[gazza2006au]

I have a Workshop manual,but it does not tell me the factory setting, eg, the number of turns out from slightly seated. And it only has one adjusting needle.

Brian a workshop manual and not a owners manual will tell u every adjustment on the engine in fine details, look up carburetor in the powerhead or fuel section than goto the spec's section look at "mixture screw" or "air idle adjustment" it will have a number this corresponds to how many turns out the screw should be after seating it

if u have high or low mixture screws on a carburetor usually the high screws are higher on the carburetor than than low mixer screws

if u have high and low mixture screws your in a bit of shit without a test tank because the high mixture screw u must have the engine going top speed u than shut off the engine and read the spark plug a bit hard if your in a river, if u power the boat back to the ramp u will get incorrect readings

[Brian Pascoe]

went out to try again,still boggy on acceleration, could not get up on the plane.Have you heard of an exhaust build up in the leg causing too much back pressure when out on the water,but runs well in a test tank

[Noelm]

Kind of doubt it's exhaust build up, best guess is you didn't clean the carb correctly, how did you clean the carb? or, you have a spark issue, do the plugs look OK when you remove them? the idle mixture screws are not your issue, how did you test it in the test tank? with a test prop? does the primer bulb stay hard when in use? does the timing advance as the throttle is moved?

[tunaticer]

It can't be blocked exhaust, it would never reach high rpm.
Being erratic leads me away from carb issues.
As stated before disconnect the temp sensor wire and give it a run.
My old 25 rude did similar thing ten years ago...erratic dropping into limp mode then out again.
New sensor and problem was solved.

[gazza2006au]

The way u tune the carburetor is by starting off with factory mixture screw settings u ideally start with the idle screw u want it to idle normal, Now in a test tank u would run it at low speeds than shut it off read the plugs make any needed adjustments to the low mixture screw according to what colour and how wet or dry the plug is running once u set this than u move on to the high speed screw u now run the engine WOT shut it off without idling than u read the spark plugs and make adjustments to the high speed screw if u need to do further test runs than u do that now, once your engine is running right thru the whole rev range and u have tan colour dry spark plugs u have now set the idle, low and high speed screws

if your testing it on the water if you rev the engine and it bogs down than rev's and takes off your mixture screw is running rich, if it cough's and sneezes your running too lean

second option is for 1 mixture screw, first bit of info is for 2 mixture screws

remember once u set your mixture screws change to a new set of spark plugs run the engine once more to confirm its all running perfect then reinstall those plugs and away u go

the way i read spark plugs is

white = to lean
brown wet or black and wet = to rich
perfect = tan dry looking like old news paper

[myusernam]

whoops didnt read OP. deleted

[ericcs]

The way u tune the carburetor is by starting off with factory mixture screw settings u ideally start with the idle screw u want it to idle normal, Now in a test tank u would run it at low speeds than shut it off read the plugs make any needed adjustments to the low mixture screw according to what colour and how wet or dry the plug is running once u set this than u move on to the high speed screw u now run the engine WOT shut it off without idling than u read the spark plugs and make adjustments to the high speed screw if u need to do further test runs than u do that now, once your engine is running right thru the whole rev range and u have tan colour dry spark plugs u have now set the idle, low and high speed screws

if your testing it on the water if you rev the engine and it bogs down than rev's and takes off your mixture screw is running rich, if it cough's and sneezes your running too lean

second option is for 1 mixture screw, first bit of info is for 2 mixture screws

remember once u set your mixture screws change to a new set of spark plugs run the engine once more to confirm its all running perfect then reinstall those plugs and away u go

the way i read spark plugs is

white = to lean
brown wet or black and wet = to rich
perfect = tan dry looking like old news paper

didn't he confirm it only has 1 mixture screw?

[Fed]

I'd start from scratch with a compression test & a free air spark test before even thinking about carbs.

[Brian Pascoe]

I will go back and do all the procedures again

[gazza2006au]

Ahh i was going by what Tuna said

[Brian Pascoe]

Finally found the problem.The spark plugs were breaking down under compression pressure. New plugs fitted and all is good.

[ericcs]

well done, that ended up as an easy and cheap fix. Compression pressure is new one for me, under load would be the common term i think. whatever, it's a good result!

[gazza2006au]

Yeah i think he meant the resistance in the spark plug were breaking down and earthing to the block very common problem even with brand new spark plugs