Boat motor troubleshooting

Loganwayne

Loganwayne

#BTL
Joined
Feb 15, 2013
Location
Clyde, North Carolina
I have a 4stroke 5hp mercury tiller for a kicker on my boat. It keeps dying after 15-20 minutes I suspect its overheating.

Took it out last weekend and it wasn't pumping water from the pee hole. Put a new water pump in it and took it out today. It had water coming out but seemed weak to me. At idle none or very minimal was coming out. When it dies and I try to pull start it the oil light flashes. Wait a while and it will start up.

It is plumbed into the main tank through a water and fuel filter like the big motor separate lines and primer bulbs from filter to each motor.

Hadn't taken the boat out in probably a year and a half or longer.

Im thinking I didnt get a mercury impeller and the rubber is softer letting water bypass some.

But open to ideas to check as well.
 
I got no idea .... but this is obligatory on the intarwebs .....

no gas.webp
 
While I do prefer @CasterTroy suggestion, I’d be looking to make sure the water passages aren’t plugged. It picks up water down on the lower unit, typically a screen or something to keep shit out, and travels up through the water pump, through the engine and out the pee hole.

I like watching this guy on YouTube that fixes and flips boat engines, he had this issue once. It was plugged up in one of the water passages in the block.
 
mbalbritton said:
While I do prefer @CasterTroy suggestion, I’d be looking to make sure the water passages aren’t plugged. It picks up water down on the lower unit, typically a screen or something to keep shit out, and travels up through the water pump, through the engine and out the pee hole.

I like watching this guy on YouTube that fixes and flips boat engines, he had this issue once. It was plugged up in one of the water passages in the block.
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I know nothing about boat motors, but clogged passageway is my suggestion as well. I know that if anything sits for long around here dirt dobbers start building nest.
 
It’s a boat motor.
SNAFU
 
Not had one shutdown do to overheating. If it's pushing any water out then it's probably not getting hot enough for overheat shutdown.

Could be ignition components are getting heat soaked and losing spark. Next time pull a plug and have someone pull the cord while you ground the plug, if no spark then you know. Could be as simple as you need to clean the magnets under the flywheel. Have had kickers get lots of salt spray and do this before. Could be you've got a bad sparkplug wire and it's arcing to the block.

Likely not fuel unless youve got a weak fuel pump. But I'm sure you tried to pump the primer bulb right ...

Nearly all my experience with small outboards that run for awhile and then quit is ignition
 
Boats only been in fresh water and engine is clean for beeing and 02.

Tore back into it today. The thermostat didnt look great. Gave it a boiling water test and it worked sometimes. So its getting replaced. Started thinking about heat soak and the coil looks original so im going to replace it while I have it apart its 24 years old. I also ordered a quicksilver water impeller in case the ones I have are to soft or wrong size (dont think they are) blew everything out with compressed air and didnt have any blockages or junk come out.
So im replacing water impeller (again), thermostat, and ignition coil. Also going to redo the fuel line quick connect with a double ended barb fitting instead of quick connect.

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Get a good ignition coil. OEM if you can. Have you checked oil pressure/oil level? It might be shutting down to save itself since you said the light flashes.
 
Wes said:
Get a good ignition coil. OEM if you can. Have you checked oil pressure/oil level? It might be shutting down to save itself since you said the light flashes.
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Oil is full and new. I ordered a new oil pressure switch just in case this one has went bad. Finding anything OEM for this motor is a pain in the ass. It has an NGK coil but cant find another one with the model number thats on it. Its a mercury motor made by tohatsu. So some parts are able to cross reference across to most mercury and some dont.
 
Loganwayne said:
Oil is full and new. I ordered a new oil pressure switch just in case this one has went bad. Finding anything OEM for this motor is a pain in the ass. It has an NGK coil but cant find another one with the model number thats on it. Its a mercury motor made by tohatsu. So some parts are able to cross reference across to most mercury and some dont.
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I’ve had good luck with straight up calling boats.net. Had a hard time finding some parts once and they hooked me right up. My old Yamaha is an 02 as well. I’ve had good experiences with them.
 
mbalbritton said:
While I do prefer @CasterTroy suggestion, I’d be looking to make sure the water passages aren’t plugged. It picks up water down on the lower unit, typically a screen or something to keep shit out, and travels up through the water pump, through the engine and out the pee hole.

I like watching this guy on YouTube that fixes and flips boat engines, he had this issue once. It was plugged up in one of the water passages in the block.
Click to expand...
This happened to me. I have a 4 stroke 25hp. Pee hole water was a trickle. Passage was plugged. Once I got it cleared, it's all good.
 
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