Weird issue - cant turn motor over

[Chilli_Wonka]

Motor is a 1990 30P manual start

I used it all day on saturday, worked perfect as always, started first pull.

Launched boat on sunday, and for some reason i can barely get the motor to turn over.... tons of tension on the starter rope. The engine is in neutral when trying to start, and i can barely get it to turn over....

Again engine was fine saturday, drove it all day and drove it up to boat laucnh when I loaded it up saturday night. There was no damage, didnt hit anything, and the oil reservoir is full, so no shortage of oil (unless oil injection failed?) But again, it ran perfect up to launch and I turned off motor will kill switch.

So obviously I couldn't get it to start and the same issue is still there. I also noticed that there is injector oil seeping form the exhust port, and there seems to be oil inside the engine cover itself... yet there are no visible cracks in tank/hoses.

Not sure if these 2 issues are connected, but looking for some advice on where to start? Im hoping its just the recoil thats the issue, but knowing my luck.....

[robert graham]

Remove spark plugs...then try to pull the starter rope...

[TownsendsFJR1300]

Remove spark plugs...then try to pull the starter rope...

+1 100% ^^^^

Sounds like oil/fuel leaked into the top end and is causing a hydralic lock. With all the plugs out, I suspect it'll pull easy and you'll get a small cloud of fuel or oil out a spark plug hole.

Pay attention to the spark plugs too, at least one will likely be filthy black.. follow the clues...


Can you list the MODEL #, it helps looking up the set up/parts, etc..

[Chilli_Wonka]

Townsends, that seemed to be what was going on, the middle plug was black and it will now turn over better. But now there's a new problem (or maybe the original issue)

I tried to test fire the motor, and when pumping the fuel ball to prime the system, fuel was spitting out of the bottom and dripping onto driveway.

What would case such a fuel leak like that? I cant see any obvious leaks on external lines, fuel filter etc, so Id assume something internal is bad? Carb floats? etc?

Thanks in advance for the advice

[rodbolt17]

a failed fuel pump diaphram will allow hydrolock the engine and drip gas out of the exhaust.

[Chilli_Wonka]

ok, i think we are getting somewhere....

the pump seems to be attached to the mid carb, and middle plug is the one that was all black and sooty, the other 2 had the nice light brown colour.

IM going to see if the local yamaha dealer here has the diaphragm and maybe see what a whole new pump will cost me... may be worth swapping the pump outright

what I cant seem to find is a part # for the pump itself.... Boats.net has the exploded views and various parts, but hey dont have a code for the whole pump

when i had my johnson 15hp, had similar diaphragm issues and after messing around, just replaced the pump with a NOS one.

[99yam40]

not sure but if attached to middle carb the housing maybe also the bowl of carb. I would open it up and inspect to see what all needs to be ordered

[boscoe99]

ok, i think we are getting somewhere....

the pump seems to be attached to the mid carb, and middle plug is the one that was all black and sooty, the other 2 had the nice light brown colour.

IM going to see if the local yamaha dealer here has the diaphragm and maybe see what a whole new pump will cost me... may be worth swapping the pump outright

what I cant seem to find is a part # for the pump itself.... Boats.net has the exploded views and various parts, but hey dont have a code for the whole pump

when i had my johnson 15hp, had similar diaphragm issues and after messing around, just replaced the pump with a NOS one.

It is shown in the illustration for carburetor number 2. The pump is not available as a separate component for this particular model.

Not all brands of motors, or models within a brand, are designed the same. It is hard to find that which does not exist.

1990 30SD Yamaha Outboard CARBURETOR Diagram and Parts

[Chilli_Wonka]

Looks like the diaphragm is the issue, looks like a bit of a rip near the middle of it where it would pulse back/forth.

Side question about oil injection..

I've always mixed my fuel and oil, never had an injected motor before now. Any harm in draining tank and going back to mixing? if not, ratio? 50:1?

[Chilli_Wonka]

Im happy to advise that the new diaphragm is installed, and after bleeding the air out of the fuel system, the motor fired right up.

Still seeing a shit-load of oil leaking out, and it looks like the low oil sensor plug (sorry if that's a bad description) is cracked.... I still don't get how oil is coming out of that plug when its at the top of the tank..... but none of the hoses are leaking, and the oil pump itself isn't either...

So again, any concerns of draining tank and mixing my gas/oil?

[boscoe99]

On a Yamaha I would never deactivate the oil pump and go back to premix. Waste of time. Plugs may foul sooner than they otherwise might and you will be wasting oil.

The seal of the oil tank sensor can wear out over time. On a 25 year old motor yours might very well have failed. Just replace the sensor. Or, try and tie strap it in place to make a better seal. Or, don't fill the oil tank above the level of the sensor seal.