Stalling tohatsu 50hp

lukewhiting · 30 August 2016, 19:00

Currently sat on the boat after about the 5th test trying to find out why the boat keeps bogging down and stalling!

So the carbs have been stripped and cleaned after each test and mixtures reset.

Have put completely fresh fuel and oil in.
Cleaned all fuel lines.
Has a new fuel tank and line and inline filter.
New spark plugs.

The engine runs sweet on muffs and at low speeds. Then will go at full speed for around 1 minute then revs will drop and it'll stall.

Couple of pulls with choke on and it starts at straight away!

It will sometimes not gain revs again until you fiddle with the choke abit.

Doesn't miss fire at all just cuts out which suggests fuel but have done everything to do with the fuel system!

Loosing patience!!! Help please!!

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Mextli · 30 August 2016, 19:03

Checked the Fuel Pump? Was causing similar issues on my Yam some time back

Under the Thumb · 30 August 2016, 19:45

Ours had the same symptoms - fuel pump diagram kit sorted it.

If pumping the fuel primer when under load stops the bogging down it's probably the fuel pump.

jeffstevens763@g · 30 August 2016, 19:56

Fuel pump same symptoms as I had with a Suzuki 25 two stroke

breezeblock · 30 August 2016, 19:59

try pumping the primer when it starts playing up this should tell you if its the fuel pump

jeffstevens763@g · 30 August 2016, 20:04

Quote:

Originally Posted by breezeblock

try pumping the primer when it starts playing up this should tell you if its the fuel pump

+1

spartacus · 30 August 2016, 20:16

You can rebuild the fuel pump with a genuine Tohatsu diaphragm fuel pump kit. Won't do any harm to replace.

I'd also check the female fuel pipe connection end. The pattern parts (if not genuine Tohatsu) are notoriously poor, so it could be a dislodged rubber 'o' ring restricting fuel flow. Check the connection locates properly on the engine and locks in position.

If it's a new fuel tank with primer bulb - then you can rule that out. Couple of years ago I was struggling to pump fuel as the rubber primer bulb was stiff. The bulbs deteriorate over time or the diaphragm fails. Quicksilver replacements are very good.

Lastly, strip off the airbox cover and check the butterfly choke valve. They are prone to seizing, so it's possibly not fully opening.

lukewhiting · 30 August 2016, 20:28

Cheers guys!

Off the water now.

Have replaced the fuel pump gasket and all looked good inside the other day but will follow your advice and buy a rebuild kit and go for another test!

Applying Choke did seem to make a difference.

If that still doesn't work I'll get all the carbs balanced and have it compression tested.

Cheers for the help! I'll keep you updated

Roflhat · 06 September 2016, 09:17

Have you tried it since? Sounds like it's drawing air somewhere. Hopefully something easy like the fuel pump, otherwise could be the base gasket

lukewhiting · 12 September 2016, 21:03

Still waiting for parts at the moment!

No UK stock so 2 weeks for one from tohastu to arrive!

lukewhiting · 04 October 2016, 18:33

So... All parts arrived and fitted.

Started engine and runs nice and smooth. Then after no more than 1 minute it'll stall as if fuel is cut off.

No miss fire, just revs drop and gone.

All carb bowls have equal fuel in them after stalling.

Will restart without priming, but using choke after 1-2 pulls.

Any ideas?

lukewhiting · 04 October 2016, 18:34

New pump fitted as per tohatsu diagrams.

jeffstevens763@g · 04 October 2016, 18:58

Intermittent fault on the kill switch?

lukewhiting · 04 October 2016, 19:02

Quote:

Originally Posted by jeffstevens763@g

Intermittent fault on the kill switch?

Don't think so, revs drop a lot quicker with that

jeffstevens763@g · 04 October 2016, 19:12

Two stroke engine ? If so air getting in crankcase ( through inspection plate or similar)

ShinyShoe · 04 October 2016, 19:19

Air getting in on fuel line?

lukewhiting · 04 October 2016, 19:29

Quote:

Originally Posted by jeffstevens763@g

Two stroke engine ?

Yeah it's a tohatsu m50d2

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jeffstevens763@g · 04 October 2016, 19:37

There was someone doing a mariner up who found a plate leaking on the crankcase drawing air,seems odd it's not burning all the fuel in the bowls on yours giving a least 5 mins running time.could it be float chamber valves sticking causing a vaccume so will only run until it carnt pull anymore fuel ?

C-NUMB · 04 October 2016, 20:13

I am not 100% sure but think also the 50 has a safety feature cutting the RPM if overheating , possible also on some other issues. So if You have a faulty sensor, this might be the issue?
Symptoms not fully supporting this but might be a long shot?

matata · 05 October 2016, 05:03

Soz to go over the symptoms again!!!

The engine starts easily?
Does it idle cleanly when on the muffs?
If you do nothing how long will it idle for?
Does the idle revs die suddenly or over a period of say 10 secs , 30 secs to what?
By pumping the bulb will it continue to idle? That is very significant?
Will it restart normally or must you use the choke?
Do you need to pump the bulb to get it to start?

My thoughts are about raising the fuel tank to atleast the height of the carbs and as a tempory measure i'd replace the fuel tubing by clear transparent stuff just to watch the fuel flow.
I don't know the engine how many carbs and how many cylinders? Pull or electric?
regards Nic