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3.0L overheat

M

mschwenz

Contributing Member
Hi guys my 01' 3.0 has ran well for a few months now, no recent overheating problems in the past few years. BUT got up to around 200F the other day before i backed it down. Ran through my checklists... Replaced thermostat, check water flow from the outdrive water pump (which was good), pulled manifold plug and saw excellent water flow.. When I come back to idle the engine always comes down to 170ish(160 t stat). Also only gets overheated when above 3000rpms. I have tried it with no thermostat too and it never even broke the needle and stayed cool (less than 110F) I'm thinking the water pump on the engine itself? Corroded/clogged t-stat housing? But before i go out and spend a lot of dough, any suggestions?

Any help would greatly be appreciated Thanks guys,
-Mike
 
The impeller in the drive went i bet.

The flapper is in the tube after the elbow not in the drive.

First do the impeller then run it.

The elbow also could be clogged. What will happen is the elbow keeps getting clogged till when you pull back the throttle it will still stay hot and melt off the rubber hose after the elbow.

Just happened to me 3 weeks ago.

I i would pull the elbow off if all rusted up the flapper might be gone also and that you got to fish out.
 
So that Water Pump has an Impeller i can change?.. We are talking the front of the motor, belt driven pump right? automotive looking?
 
Oh I read that wrong Cheifalen, I have really good water flow coming from the lower pump into the thermostat housing, Thats why Im trying to rule that out plus the boats in the water. Also i pulled a plug out on the bottom of the exhaust manifold and ran the engine and water spurted out like when you put your thumb over a garden hose, Ill have to check out this flapper valve. Riser was off last year along with entire manifold setup looked pretty good still, not many hours.
 
Maybe I`m off base here but if he pulled out the thermostat and it only got up to 110 F without it, does it not make sense that it may just be his thermostat not opening properly and if a person is going to try the trial and effort method of repair that some seems to be advising, I`d start with the obvious and least expensive item.
 
the t-stat out the needle should not move at all.

How i know ?

I don't run with a t-stat.

But that's just me.

And yes Dock was right i read his post wrong, the flapper could fall down into the tube and get stuck in the opening or as he said fall into the drive and stick before the prop.

No power steering cooler ? But then again that's the first stop for raw water before the t-stat.

Here is what happened to me 3 weeks ago first time out this year, ran the boat on the bay and when i hit 3000 rpm the motor over heated. The rubber tube on the riser melted off.

I had the boat started 5 times in my driveway before that no indication of the needle moving.

Riser was clogged solid with only one passage open.

I have no flapper never did.
 
Took off the the pipes that lead down to the flapper valve and found the remnants of what was the flapper (metal cross bar and some torn up rubber gaskets) so you guys hit the nail on the head, Ill have to find time to haul the ship and find those pieces. I know Chiefalen that you dont use a flapper valve, What is it there for? will i sink the boat in the slip without it?
 
The rest of the flapper could be lodged in the exhaust bellows, in the upper unit or in the lower unit. The flappers supposed job is to stop water from flowing back into the engine if you exercise an abrupt stop. (They never work to begin with)

In short, your boat will not sink if they are removed.
 
Glad you found the problem, but, and someone correct me if I'm wrong, don't he specs for a 3.0 call for a 140 stat?
 
with fwc or without.

New 3.0 have fwc as a option.

IF YOU USE A T-STAT merc calls for a 140. Omc a 160. Both 3.0 both exact same blocks and all.

Dock called it first he should get the thanks.
 
OK got some time to do this work, found the half the flapper and rubber as they fell out between the upper and lower units, other pieces scattered as well, replaced impeller, but looked good as new anyway. Its now running 175-185ish, hasnt taking off into the 200 range but im a tad concerned, If memory serves me right this engine ran around 170/175 all the time. Am I just being overly concerned?
 
200 hrs, riser is real cool to the touch, never gets more than warm, Definitely not clogged solid but I would probably change it in the fall
 
Are all these temps you are reporting just from your temp gauge on the boat?They are not famous for their accuracy. Has the motor actually shown any signs of overheating. Do you have another method of checking the actual operating temperature?
 
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