View Full Version : Yamaha sterndrive 43 V6 OVERHEATING

06-23-2006, 07:45 PM
"Ok - just joined this forum and Im having a heck of a time diagnosing the problem with my EBBTIDE boat with 4.3 Chevy V6 stern drive,

PROBLEM : Submerge lower unit in a 35 gallon bucket of water. Engine starts right up - but heats up to 190 within 5 minutes, And theres no stream of water peeing out the lower unit weep holes like it should I get just spitting of air .

Checked ALL belts ( tight )
New Impeller
New circulating pump
New Thermostat (even tried with no thermostat)
Checked Risers (fine)replaced gaskets
Checked all coolant lines for implosions

Flushed weep holes in lower unit with garden hose from the RISER ( nice flow )

Removed output hose from impeller pump and she's pumping.

Removed coolant hoses from both sides of power steering oil cooler and flushed it AND the hoses . Checked the screen on the cooler as well - all clear.

Circulating Pump is pumping.
Bypassed the impeller pump and ran a garden hose right to the thermostat housing - engine temp was NORMAL and weep holes in lower unit were weeping.

Is my power steering oil cooler clogged ?

My thermostat housing has 3 pieces
the cover - the middle( that the therm sits in)
and another block that two houses connect and run to UNDER the risers.... could this be blocked ??

What are the symptoms when the impeller pump fails ?? Leakage ???
I noticed that the impeller pump pumps at different speeds.

Look guys - I wasnt that familiar with these stern drives but in the past week Ive had quite the crash course - any help at all will be appreciated . Rob from Plymouth Ma."

05-30-2007, 10:54 PM
I am in the same boat looking for answers. Something that I have seen in other posts all over the place is this. there is a line that comes in from the transom. If the line is cracked it will pull air and not allow the seawater pump to do its job. I am still at the stage of replacing the impeller on the seawater pump mmyself. let me know if you have a good line on parts for the 4.3. I am looking for parts now.

10-13-2008, 04:31 PM
Check plastic thru hull fitting at the transom for the water line. I have one that is split therefore not picking up water. Also check mating surface between bellhousing and upper drive. Make sure oring has a good groove.

10-13-2008, 08:28 PM
Install a thru hull with a clamshell scupper somewhere easy to get to in the bilge. Attach your incoming suction line to it and you will end the suction problem from the outdrive.

12-31-2008, 02:33 AM
"Brass air fittings

Now that is a lot of brass air fittings

http://www.liangdianup.com/subpages/airfitting_1.htm ("") there is just about every

of air fitting that you could want. Wholesale prices too. I guess these could be

used as small water pipe fitting also. I
used some of the parts to make my babington wvo burner."