Out board running sluggish

Hy guys,

recently out in the bay everything was running fine going well almost full throttle and then the motor just bogged right down. Will idle normal and runs fine at just under 1/4 throttle. Second you give it any more it starts to run terrible coughs and splutters and won’t clear.

if you turn the key off give it a few seconds start back up and full throttle it is would run perfectly for 15-40 seconds sometimes 2 minutes etc but then would go back to coughing etc. after doing this time and time again trying to get home it for lack of a better word cleared itself and just ran perfectly again.

But after a while back in the passage it started again.

Only just been serviced.

Outboard is a 99 johnson 50 s stroke.

mixing fuel at 50:1 as recommended

there was a bit of oil around the carby seals and the plugs had in burnt oil on them if that’s any indicator?

will try and add the video of it running rough

https://vimeo.com/249159912?ref=em-v-share

video uploaded here

Had a similar problem with mine yesterday, took my boat for its first water test after working on the electric wiring for about 3 weeks and it took off without problems, but within 5-10 minutes the motor went in to a sort of limp mode, anything more than 1500RPM and it wouldn't go any faster and didn't sound right, turns out the breather on the fuel tank is blocked somewhere and was causing a vacuum in the tank so fuel wasn't getting to the motor properly, opened up the filler cap a little bit and problem solved. Now just have to find the blockage on mine.

Might be worth having a look for something similar, mine gave me a clue when I squeezed the primer bulb and it was soft. Pumped it up and it ran normally for a minute or so then back to limp mode again, checked the primer bulb and it was soft again, that's when I opened up the filler cap a bit and no more dramas.

Cheers

Ed.

Few things I would be looking at. Fuel line and tank first up. Try the tank lid as mentioned then either borrow or buy replacements and trial them to isolate the fault to either fuel delivery or the motor itself. If it is the motor, there is a good chance you have had a bit of shit get into one or both of the carbies and it only creates enough suction to pull it into the jets under high rpm.

Thanks guys that will give me some where to start. Could be just it. I’ll keep you posted

Also look for air in the internal filter. If you have a leak somewhere it will suck air in without necessarily showing a fuel leak. Motor will normally start OK after pumping the primer bulb, might run OK for a few minutes, then bog right down. Similar to having the vent closed or a breather blocked.

check the fuel line hose pick up inside the red tank, the clear hose can kink just above the strainer

If the motor is pumping plenty of water and the powerhead is not hot to touch then pull the temp sensor wire out and give it a run.
It will not go into limp mode when disconnected.
Common failure with OMC engines of that era.
I have replaced my temp sensor 3 times now.

Quote:

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Originally Posted by EdBerg

Had a similar problem with mine yesterday, took my boat for its first water test after working on the electric wiring for about 3 weeks and it took off without problems, but within 5-10 minutes the motor went in to a sort of limp mode, anything more than 1500RPM and it wouldn't go any faster and didn't sound right, turns out the breather on the fuel tank is blocked somewhere and was causing a vacuum in the tank so fuel wasn't getting to the motor properly, opened up the filler cap a little bit and problem solved. Now just have to find the blockage on mine.

Might be worth having a look for something similar, mine gave me a clue when I squeezed the primer bulb and it was soft. Pumped it up and it ran normally for a minute or so then back to limp mode again, checked the primer bulb and it was soft again, that's when I opened up the filler cap a bit and no more dramas.

Cheers

Ed.

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Bait knife looks blunt :)..

Quote:

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Originally Posted by Volvo

Bait knife looks blunt :)..

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Sorry, no idea what that refers to.

Quote:

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Originally Posted by Volvo

Bait knife looks blunt :)..

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Hahahaha a little humour always wins

Doesn’t get hot and pumps heaps of water will defiantly try that tomorrow

Quote:

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Originally Posted by tunaticer

If the motor is pumping plenty of water and the powerhead is not hot to touch then pull the temp sensor wire out and give it a run.
It will not go into limp mode when disconnected.
Common failure with OMC engines of that era.
I have replaced my temp sensor 3 times now.

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for peace of mind, you can buy themomelt wax sticks that are rated to melt at different temperatures to check if your powerhead is operating at normal temp, or over!

Wasting your time, limp mode will pull it back to ~2500 rpm not bring it to a grinding halt.