Mercruiser 470 3.8 LT. 4 CYC. OVERHEATING

P

pacmanII

New Member
I posted this question once before and got several things to check out.
All suggestions where greatly appreiciated---BUT--- nothing helped.
Heres what has been done so far--
1. New Impellor[intake in out drive]
2. New 4 inch Heat Exchanger
3. New Thermostat
4. New gauge and sending Unit
5. Head removed --Magnafluxed--Surfaced--and replaced
6. Fresh water side of cooling system flushed left to right--and-- right to
left with air pressure and water.
7. Anti freeze side of cooling system done likewise.
8. Circulation impellor checked--Gear driven off of cam
9. Oil.Filter changed
10. New Anti-freeze put in cooling system
11. Checked compression 150lb. plus on each cyclinder
12. Pressure tested cooling system--pumped up to 15 lbs.--Held overnight

This boat has the Salt Water Cooling System.
Any suggestions of things to check or problems to look for would be
greatly appreciated. The repair manuel in my brain of things to check and
test just got to the last page. PLEASE HELP!!!!

Thanks so much in advance for any help in this matter. PACMAN II
 
dave

dave

Active Member
i seen poeple look for this type of problem before and then come to find out that the impeller fell off thier engine water pump. it wouldn't hurt to check.
 
Chris E

Chris E

Member
have you checked the water hose in the bell housing? the rubber will rot, causing the engine to overheat - very common problem and i didn't see it on your laundry list.
 
Chris

Chris

Administrator
Staff member
dave said:
i seen poeple look for this type of problem before and then come to find out that the impeller fell off thier engine water pump. it wouldn't hurt to check.
Click to expand...
Agreed. I'd revisit the water-pump and make sure it's good to go. We've seen all kinds of stuff over the years and the most common thing that comes up, even after it's been serviced, is issues with the water pump itself. I've heard of people installing them backwards, run them dry right after the install and burnt them up, etc. etc.

As Chris E said as well, sometimes the waterhose or water tube can be an issue too. On outboards, a common problem is that the tube doesn't get married up and set properly into the coupler, or sometimes the coupler is dry rotted and leaks water.

I would go back to square one and double check the pump itself.

-Chris
 
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