165 Mercruiser Over Heating

[Camille]

I have an 88 Renkin Cuddy 20ft 3.0L Mercruiser 165 I/O. I put it in the water and almost sank it because there was no drain plug. I put in drain plug, took it back to water. the engine runs fine, then all of a sudden it starts to smoke in the cuddy. I look to the stern side and see water coming into the boat. the engine is too hot to start so i didnt force it. I vertially swam the boat back to the dock; by then its full of water all the way into the cuddy. There is no hole in the hull and doesnt seem to be at the transom but i can't see behind that. There is a hole in my bilge pump hose, but i didnt have it on. The 50/50 antifreeze that i filled the radiator with is now almost gone. After cooling, the boat starts on first crank on the Rabbit Ears water hose flusher, the temp remains fine. Where did the antifreeze go ,and where did the water come from into the boat? The hull is fiberglas. How can i tell if the transom is one of the problems for the leak?

 

[longstand]

Re: 165 Mercruiser Over Heating

first of all. same thing happen to me.

Just put the boat on the water with the trailer.. run the engine on neutral and warm it up.. see where the water is coming from...

 

[Bondo]

Re: 165 Mercruiser Over Heating

20ft 3.0L Mercruiser 165 I/O.

Ayuh,... I Don't know where your boat is Leaking,... You have to LOOK...

As for exactly What you have,... It Ain't a 3.0l 165hp,... There's No such thing...
By your discription, you have a 470, the dreaded 3.7l Merc. motor...
And,...
By your discription, it needs Alotta Work...

I believe you can find a copy of the factory Manuals up in the Adults Only section....

Good Luck,+ Welcome Aboard....

 

[searay3]

Re: 165 Mercruiser Over Heating

Check the oil. Antifreeze may have gone there, it'll look like chocolate milk. Any history to this boat? Is it new to you? The reason I ask is it is not unusual for someone to sell a boat with a cracked block and not say. There are drain plugs on the motor. Make sure they are there and closed. Get a manual, you'll need it. Backing it in the water and running in neutral on the trailer is a safe way to check for transom leaks. If you know someone with a cooling system pressure tester, you can put water in the heat exchanger and pressurize the system. If the leak is external you will see it. If not, you have a head or block or exchanger issue (internal).