Mercruiser 3.0 choke at shut off, overheats, smoking carb

[Donboating911]

Big Big Problem please help..

I've read a lot on here and everyone seem to have so much good ideas and skills..

i have the 1998 1750 LS Capri Ski with the Mercruiser 3.0 Alpha one.

It will start up fine and idle fine as well. It will over heat to around 225 the carb will smoke from the base and and also kind of smell like gas some smoke from side of egine The problem is when i turn off the egine it chokes and shakes violently before shutting down. When this happen i investigated; the big water hose is very hot and feels like no water in it at all, restart the engine again now no air comming from the propeller it used to, not spitting out water either i dont know whats going on im new to the boat community please help..

before this all happen earlier the same day i found out that the gear oil outdrive was low there was nothing in the reservoir on top. I open the top screw of the outdrive and stick a plastic stick in there and there is oil At the opening but at the top reservoir it was completely empty so i top it off at the reservoir.

Also at the same time i got a big bucket fill with running water holes to submerge the outdrive and started the engine. This is when it all started over heating smoking from carb smelling like some gas and choking at shut down

Anyone please help

thankyou so much and god bless

 

[achris]

Hello Donboating911, and :welcome: to iboats...

The 'shaking violently' at shut down is the engine 'running on' or dieseling due to it being SO hot!

Putting a bucket of water under the drive is not the right way to run the engine out of the water. You need to get a device called a flushing attachment... Put it on the drive water pickups and turn on the hose to FULL...





Having run without water for so long, you have likely destroyed the impeller in the drive, and burnt up the exhaust shutter, and the rubber tubes in the exhaust system... And at that hot, I wouldn't be at all surprised if you blow the head gasket too...

Chris.........

 

[Donboating911]

Omg that dont sound good at all i do have the flush attach i saw a video on youtube where a guy used a bucket so i tried it . Im praying that the head gasket is still good. Please tell me what can i do at this point. Thankyou so much in advance

 

[Rick Stephens]

1: Pull the drive

2: Inspect and replace the impeller. (if the impeller is missing pieces then you will have to find them in the cooling system since they can block flow)

3: Since you have to drain the outdrive to replace the impeller, when you reassemble, but before refilling, is the time to pressure test it. Find out why it is using oil.

4: Pull the elbow off the top of the exhaust manifold and inspect the rubber exhaust boots and shutter.

5: Do a compression check on the motor.

 

[Donboating911]

Thankyou for the help guys.. i really do appreciate it

Why did it over heat in the first place ? Is it because i use that bucket of water under the outdrive? This motor never had any problems before it starts right up every time. We were trying to go out this weekend i guess its cancel. This sounds like a pretty major job i will try to tackle it somehow. Is this a difficult repair ?

 

[Rick Stephens]

Water needs to be above the level of the cavitation plates, the pump needs to be totally submerged. The water pump in the outdrive is vented to allow it to self prime when under water. It cannot pull water to prime at all since it has a hole that vents out any air in it. So if all you did was submerge the intake, the pump was high and dry. Even if you got the water up to the pump, if it wasn't submerged quite a bit, then it would pull air and stop.

Water is the lubricant for rubber. It doesn't take long running dry to fry a rubber impeller.

You have a learning curve. The repairs take making and buying a few special tools. Not particularly difficult, but needs some study.

 

[Donboating911]

Thankyou for the advice i have much to learn i will try to work it this weekend if i have any other questions or if you have any other tips or tricks before i try to opent it up please let me know im willing to learn. Thankyou again and god bless

 

[Rick Stephens]

Biggest tip: read all about it in the Adults Only section and watch achris's videos.