Cooling system

"I have a 3.0 litter mer just

"I have a 3.0 litter mer just wanted to know where i should start to find my cooling problem.The boat I just purchased was cooling itself fine for about 40 min(175 degress) then the temp started to rise to about 220 .I then shut the motor off .Where should i start water inpeller, water pump, thermostat ?Please respond I could use the help and if it is the impeller how hard are they to change (advice on that would be nice)are there any ways to tell what is bad impeller ,pump,thermostat. thank you"

The blades have probably came

The blades have probably came off your water pump impeller in the outdrive. Books are available to show you how to replace it. Check the marineengine.com web site for parts. Water pump impellers are a high maintenance item. Never never run a motor without a water hose attachment or being submerged in water. Water lubricates the pump and by just starting up the engine for a few moments can cook the impeller...........blades come off really fast then! Since your engine was cooling fine and then all of a sudden overheated would make me believe it is an impeller. Also check the thermostat for proper opening.

A little more history may be h

A little more history may be helpful. Any idea how old the impeller is or was?
Were you running through any weeds or something and maybe blocked the inlet screens on the outdrive?

"well the history i just bough

"well the history i just bought the boat and i was running it on water muffs in the drive ,I am running the boat to see if I have a cracked block,I have no idea on the age of the parts but the boat is an 1988 ."

"do You think asking the same

"do You think asking the same question three times will produce better answers? take it to a shop, pay the money, and see a shrink."

"Darren:
Since you were run

"Darren:
Since you were running it @ 175 deg. for 40 mins. on ear muffs in the driveway and all of a sudden the temp rose to 220 deg. could have occurred by the ear muffs vibrating off of the O/D water inlet enough to lose full pressure.

Did the boss start the washing machine or someone in the shower cause a reduction in water pressure at the hose? A garden hose on full pushes alot of water into the O/D and the impeller can be defective and yet the engine won't overheat. Been there and done that with my first boat in 1981. It worked in the driveway but not in the lake.

Try it again and keep an eye on the muffs. If it stays at 175 deg., take it to a lake and run it at the dock. That will tell you if the impeller is shot.
Guy"

"Darren,
Your first step out

"Darren,
Your first step out to be to buy a decent service manual and spend your next day off reading some of it. Typically the first couple of chapters have some good verbage how things work and the basics of marine propulsion.
You don't have to have a PhD in marine engineering, but some general of knowledge goes a long way in identifying and eliminating problems.
It also helps us figure out just what exacly you're asking.
So far we have:
- looking for a cracked block, possible cooling system problem.
- overheated in the driveway (rapid increase in temp after running at NOT).
- no record of previous maintenance.
- 1988 3.0L model,
- possibly first time boat owner.

We could cover a lot of ground on this one!"