Sudden overheating problem

[donnyt01]

1984 SeaRay with a 120hp Mercruiser I/O Alpha 1 I believe.

I currently have my boat on a lift about 5 miles from the ramp so I'm trying to figure this out without having to get a tow and put the boat on my trailer and take it home.

Fixed a fuel line leak today and lowered the boat till the lower unit was in the water and the bottom of the hull was touching. Fired it up to make sure fuel leak was fixed. After a couple of minutes, lowered the boat (Still running) into the water. Backed out of the slip and took off. Noticed hot engine smell (engine cover still on dock so I could watch for fuel leak) and temp gage was at 210. Shut down and looked around to see what's up. Nothing looks out of place so I let it cool down a bit and try again. Same thing. Pulled the vent plug on the thermostat housing and lots of hot air came out but no water. No heat exchanger, raw water cooling only.

Limped / paddled back to dock and hoisted boat and went home. Looking around on here for answers and thinking impeller failure.

Is this probably the issue?

Will running the boat this way always cause a problem?

Can you replace the impeller while the boat is on a lift?

Will SeaTow tow me back to the ramp if I tell them where I am?

Thanks for the answers. Feel free to ridicule me if it makes you feel better too.

Donny

 

[Gary H NC]

Re: Sudden overheating problem

I have a feeling it was not low enough in the water when you first run it.
Just submerging the water intake vents is not always enough and can cook the impeller.
Remember when running it on muffs in the driveway you have water pressure pushing it up to the impeller.

When the boat is fully setting in the water the impeller is submerged.

Getting it on the trailer is the best option.It is way too hard working on a drive when hanging in the lift.
I have lost several tools and parts trying that.

 

[EddiePetty]

Re: Sudden overheating problem

...in total agreement with Gary!!

If you have potable water near your lift, raise the boat out of the water and connect the muffs. I'll just bet the boat doesn't run hot on the muffs...proof that the impeller/pump housing is shot.

 

[tomlida1]

Re: Sudden overheating problem

Well, you bring up an interesting question about replacing an impeller while at the marina on a lift. Im about to put mine at the marina on a lift myself and need to replace the impeller as preventative maintenance.

I was thinking since houseboats need the same replacement, and people that have boats without a trailer have to replace theirs as well, why couldn't the marina mechanic do it without you having to pull it out, etc..?

There are plent of 30+' boats in marina's and you dont see them popping theirs out of the water to replace their impellers.

 

[wanna-be]

Re: Sudden overheating problem

im sure the marina mech will do it the easiest way possible but you pay $$$$ for that convenience.

 

[howlnmad]

Re: Sudden overheating problem

I gotta go along with Gary as well. You fried the impeller.
No-one said you can't change it out while hanging on a lift. The conveinance is what was mentioned. You planning on wading in to do it or tying a dinghy up behind and working out of it?

 

[donnyt01]

Re: Sudden overheating problem

I would have done it from a small tin boat, but am planning to tow it to my trailer later today and do it in the driveway.

Bad weather may be coming anyway.

Donny

 

[jackd1023]

Re: Sudden overheating problem

If you must change impeller on the lift use a raft under the drive to save tools, parts etc. I had to do this once lol.

 

[donnyt01]

Re: Sudden overheating problem

Boat is on the trailer in my driveway, storm is coming anyway. Got the lower off last night and yes, the impeller was totaled. Found most of the pieces in the lower unit were the water is supposed to come in. Flushed water through the engine to try and remove any additional pieces.

Picked up the new water pump kit and will install tonight. Should get to run it on the muffs tomorrow and put it back in the water Saturday after the storm passes. Thanks for all the help!

Donny

 

[EddiePetty]

Re: Sudden overheating problem

....and while you have the lower unit off...examine the exhaust passages for pieces of a destroyed flapper (shutter) valve!

 

[donnyt01]

Re: Sudden overheating problem

....and while you have the lower unit off...examine the exhaust passages for pieces of a destroyed flapper (shutter) valve!

Not sure what I'm looking for here. Can you elaborate?

Also, is gasket sealer required on the water pump gaskets? I've seen it written up both ways.

Thanks,
Donny

 

[EddiePetty]

Re: Sudden overheating problem

Not sure what I'm looking for here. Can you elaborate?

...certainly.

When an engine is starved for cooling water, the exhaust temperatures in the risers, boots and bellows soar. The most frequently affected component is the rubber exhaust flapper (shutter) valve located inside the 'Y' pipe beneath the rubber coupling from the riser. The valve is mounted either on a shaft or hinge pins directly inline with the exhaust. The cooling water starved exhaust cooks this flapper and it breaks apart and jams within the exhaust passages to the outdrive. The two most common lodging places are at the turn through the transmon (viewable by removing the complete outdrive) or within the foot of the lower unit (viewable either through the prop or removing the prop).
Somewheres on this site one of our members has previously posted a picture of a flapper lodged within the foot, but I can't find it at the moment.