Yet another overheat at WOT question

[kameika]

I'm really sorry for cluttering this board with questions..

Everyone. I posted recently about an overheat problem on an OMC Seadrive 2.7L (225HP V6 Looper.)

Under WOT conditions and slow reverse, I was getting an overheat alarm.

At 3500- 4300 (cruise speed) -- never a problem. Tell Tale: Good pressure.

Starboard side seems hotter than port side.

I can do the three-second rule on the port side (fingers for three seconds on the cylinder head.) Starboard side? Hotter. 2-3 seconds is pretty uncomfortable.

I pulled (again) the thermostat from Starboard side.

For interest, I started the engine -- for only a second or so.

Exhaust gas came out of the thermostat housing.

Hmmmm.

Do I have a blown head gasket???

Thank you again.

KenRBNJ

 

[ezeke]

Re: Yet another overheat at WOT question

It could be a bad gasket but it may be a symptom and not the cause. I would expect that the gasket blew because of the overheat.

Replace the gasket and rework the thermostat right down to the gasket and seat.

Water pumps are not selective, so look at the thermostats.

You could also be running lean, so check for signs while you still have time.

 

[kameika]

Re: Yet another overheat at WOT question

Okay. I appreciate this.

I'll take your advice. I am going to pull the boat out this afternoon.

My plan is to:

a. Compression test the engine.
b. Pull the LU, inspect the pump
c. Change the thermostats and thermostat seats

I'll report back on this forum with my findings. (Like I wish everyone would do. )

My ambitious goal is to be done today..

 

[kameika]

Re: Yet another overheat at WOT question

Okay. For the record this is the straight poop:

Very sunburned.

Maybe someone can get some good advice:

a. Pulled the lower unit off. Inspected the pump. One bolt was loose, of 4. Small gap between the pump housing and the lower unit. Probably leaked a little water. Drilled, tapped, added 0.25" - 20 (quarter-twenty) heli-coil.

b. Noticed some exhaust blow-by on the exhaust pipe fitting. Cleaned and re-sealed. Reinstalled on the lower unit.

reinstalled the lower unit.

c. the bottom of the boat was COVERED in Barnacles. It was AWFUL. The Navesink has become cleaner over the years. Inviting dolphins and all that jazz. I have never seen so many barnacles..

d. Compression test, all cylinders. 115lbs per cylinder +/- 5lbs. I think the head gaskets are fine.


Reassembled, cleaned, pushed out the boat. Ran nicely.

Hit a log. F^ck. Par for the course today.

..Also realized. If I decide to not be an engineer, I can become an outboard mechanic. I was approached a few times to fix others' engines.


I hope this helps someone.

 

[fishinhardwater]

Re: Yet another overheat at WOT question

well did your overheat alarm go off after you did all that work?

 

[kameika]

Re: Yet another overheat at WOT question

Missed one detail:

Also found one of the "Thermostat Seats" was pushed in funny. ..Probably causing "blow-by." Fixed that too.

Could have given the port side more cooling water at the expense of the starboard side. Hmmm.

Ran the engine at WOT. It seems FINE.