Need advice on 3.0 after very brief overheat

[insttech1]

I fished a very shallow Canal the other night with trilling motor. On coming out I lowered the motor started it up and slowly made my way out. When I got in deeper water I went to get up on plane and something wasn't right. So I stopped it raised the motor and pulled somebody's 3 feet of rope out of my prop. After that I got up on plane just fine but after 200 yards the temp was 185 and climbing quickly so I killed it. It did rise after killing engine. I used the trolling motor for the mile back to the ramp. I pulled the water pump and the impeller is fine and I ran water through the drive and it came out the hose in the engine compartment just fine. I ran it on muffs and it got up to Temp and stayed there and did not overheat. The only thing I noticed on muffs was the drive water drain ports on the left and right were dribbling water but not spraying really heavily. Water poured out near transom as usual. Is there anything else I should do before I do a lake test? I do not understand what caused it to overheat and this has never happened before. And there's nothing stuck in or around prop.

Thanks much!

 

[Maclin]

Just espousing a theory here...Maybe the intake grates had a plastic bag or towel or some other artifact "from under". The suction would have kept it there, then when you backed off suddenly the suction went away and the debris cleared by wave action. You may need a close-to-the-dock test run to bear out this theory.

Hope it is/was something like that, and you are good now. Even if that is not it, you did all the right things when that happened, probably saved many $ down the road.

 

[insttech1]

OK thank you much!!

 

[insttech1]

Quick update. Idled fine and got to temp at ramp but overheated within 250 yards when running. Got up on plane fine so power seems to be there. Any thoughts? Severe damage or blockages somewhere?
Thanks!

 

[Bondo]

Ayuh,..... Start yer investigation by replacin' the impeller in the raw water pump, 'n test from there,....

 

[insttech1]

Already checked first thing. Good. And water thru drive into engine compartment. Also good

 

[insttech1]

Need troubleshooting flow chart for overheating 3.0 with sx drive

Hi All,
Checked Don's posts; didn't see what I was looking for. Could have missed it?

Had another post. Overheating did not go away so starting this one.
The cause: sucked 3' of trash rope in prop at idle in gear in shallow water.
Cleared rope; boat goes up on plane; overheats in 200 yards. As in gauge heading to max.
Engine killed and headed to ramp w/ trolling motor.
Disassembled water pump; impeller good. Ran water from muffs through
drive into engine compartment hose also looks good (obviously can't measure).

Runs up to temp on muffs and lake and looks good IDLING in NEUTRAL.
Water from transom and drive seem to be OK.
Any power to her at the lake, and she overheats within 200 yards.
Gets up on plane as normal, maybe just a hair slow.

So...next steps....??
1. Can a partially spun prop hub cause this? Or I messed up my drive?? (only overheats when in gear)
2. Pull plugs on block and see if debris in there like there is end of season winterizing?
3. Start tracing out water hoses to what I can get to and see if there's debris in there?
4. Comp test engine?
5. Start looking into serious issues; head gasket, riser, manifold, head, block?

Just not sure of good steps from here, so I appreciate your help!!
Thanks All!!

 

[insttech1]

Created new post asking for general overheating troubleshooting chart. Thanks for the help!!

 

[GA_Boater]

Please don't start new topics on the same issue because advice is scattered and tends to be confusing for all involved.

A spun prop can't cause overheating.

You said you checked the impeller - Did you reuse or replace it?

Checking compression is not a bad idea after overheating.

Look at this for cooling system - http://boatinfo.no/lib/volvo/manuals/30_gl_gs.html#/130

 

[insttech1]

OK on new post. I assume new one deleted?; didn't see it.
Thanks for info on prop.
I reused impeller; nothing looked amiss; impeller kit on way; delivery tomorrow.
Thanks for the link!! Will look into.
Also starting to wonder if mud/muck got into thermostat...
General question--how long does engine have to overheat before seriously bad FUBAR results?
I killed engine both times upon signs of temp rising above normal.

Thank You!!

 

[Maclin]

The engine can usually go a few minutes or more if oil level is ok, but the rubber exhaust components will start to melt and can catch fire, sometimes taking other cable sheaths and wiring along with it.

 

[insttech1]

Thanks Mac. Did engine compartment visual inspection. Found no indication of heat anywhere I could see. Opened compartment on the water when this happened and there was a warmth and an odor, but nothing terrible or "smoky". Oil level good and no water. By rubber components are you referring to bellows as well? Thanks!!

 

[Maclin]

Yes, the big rubber hoses that connect riser to exhaust pipe inside, those cannot last with just hot exhaust gases and no water exiting with the exhaust. An engine has to get pretty hot before heads warp and gaskets blow out, you could probably tell if that happened, lots of new smells and vapor trails right after.

 

[Maclin]

Oh, and sorry it was not the temporary problem with just the intakes blocked

 

[insttech1]

Yeah me too.... Sigh.... Me too!

 

[insttech1]

Thinking out loud waiting for parts to arrive....

So I have read and studied the water diagrams as attached in the link above. I pulled most of the hoses and water pump last night (in anticipation of the new impeller being here today).

This is my thought process: something happened nearly instantly when I got the rope in the prop and I was shallow. I can logically think of only 3 things:
1. I sucked up a bunch of debris (muck) and it's blocked off some passage in the block/head/manifold (probably not drive).
2. My thermostat is not opening (makes a little more sense to me because idles OK but only heats up under big throttle, and the hose between the thermostat and the manifold is the only one anywhere that is more "pliable"--perhaps heated.)
3. My block mounted water pump failed (I think not likely?). I assume it's a metal fan blade type pump.
4. Bad impeller (although looks really good, turns in housing well, creates suction sound, etc...)

I will replace the impeller as suggested. No problem. But I'm not convinced yet that will fix her....most definitley hope I'm wrong haha!!!

And if I'm not, can I remove thermostat (test that too), and also use a hose to pump water through block passages/head/manifold without
filling the cylinders with water??


Thanks Everyone!!!!

 

[HRSAUTO]

I had the exact same thing happen to me the rope deal and all same overheating in the same amount of time. I have already changed the t stat with no luck.I have heard about the plastic exhaust flapper melting and falling down and blocking the exhaust and causing back pressure issues.

 

[insttech1]

So you haven't found a solution? I have had no "flapper" for about 3 years. I removed it because of advice here. And it was deformed/not moving. I'm doing more troubleshooting tonight. Thanks

 

[HRSAUTO]

No i have not but will continue on it this evening

 

[insttech1]

So I installed the impeller and ran a few water checks by running a garden hose through various areas.
I did have some junk drain from manifold drain port when flushed from entry point. A lot...? Don't really know yet.
I have yet to do lake test.
However, upon reading the theory of operation (attached, and full schematic) I am seriously confused.
It states that "no water" will exit the system until the thermostat opens.
The diagram seems to support this.
However, my boat (always has!) dumps water from the transom and the drive drain ports instantly upon startup. (obvisously thermostat closed).
Any input on this??

Thanks Much!!