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Please HELP!!! Engine overheating in neutral but not in gear...or under load

lgdpt

lgdpt

New member
5.7Giphus Start the engine and at around the 20 min mark it slowly starts increasing temp to 200+. As soon as we put it in gear, the temp drops to 160 within 10 seconds. Back to neutral.... temp slowly starts climbing again. It never overheats while motoring at idle or at 3000 rpm....just when in neutral. Brand new risers and manifolds, Impeller is fine( I checked).

Any advice? Thank you in advance!
 
There should be no correlation between being in neutral and in gear. The sea water path is un-changed in either scenario.
Using a IR gun, see if the temperature is actually changing.

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That's a NEW one!!!! Not really.Check for loose connections. A loose ground on ANY guage can bleed over to the temp guage. Worked on a boat,2 years old.The temp guage would read crazy and no matter what was done it wouldn't stop.Turns out it was a wire pinched at the rear of the motor.Not saying this is the problem but who knows???
 
Thanks Jerry, I will check that.

Im also thinking about the fins inside the circulating pump... If that pump needs replacing....maybe....
 
I forgot to mentioned this (not sure if it matters) but even in the driveway with the outdrive in a tub of water, the exact same thing happened... 20min in, the engine starts creeping up in temp... Increase the RPM and the temp steadily decreses back down to 160 and hold there....

Im borrowing an IR gun today to verify, will report back!

Thanks again
 
If you find that you are actually over heating with the IR Temp gun, I would pull the circulating water pump off the front of the engine and take a close look at it.
 
Ok, it IS overheating (checked with IR gun). It ran great then at 20 min or so it started rising. Starboard side riser was 185 and port side was 205. Thermostat housing was 185. I’m going to pull off the circulating pump this week and replace it. But still not sure why one riser went 20 degrees higher than the other (both brand new).
 
glad to hear about one side hotter being normal... I will check the pump and report back what i find...Thanks again.
 
The 5.7GIPHUS is what I consider to be still in the AQ series family. This means that there is a pivot tube, an upper water neck fitting, and a slightly different style lower pivot tuber sealing ring.

If your 5.7GIPHUS is true to it's model designation, it will use the belt driven sea water pump, and it will be an "open" cooling system... (aka Raw Water cooled).


I believe that when we test for a suction breach, that we use suction (not unlike "pressure").
Put a shop vac on the sea water pump suction hose.
Use shave cream at suspect areas.
If the shave cream disappears, you likely have a breach at/near this area or areas (plural).



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Ok, I think Im following you Rick... I get the Shaving cream and the shop vac part....

So you think I need to check between the sea water pump and the outdrive...correct?
 
That is correct!

Your drive is likely a DP-C1 or a SP-C1 similar looking to this drive.


Your water neck fitting may be the plastic version. These can crack, whereas the aluminum water necks will corrode.
If yours is plastic, your lower pivot tube will seal differently from the earlier fat O-ring style.


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That looks like mine (hard to tell...min has been painted black)... How do I get at the water neck fitting from the engine compartment or outside the boat? (not sure where it is).

Thanks again for all your help!
 
You check the impeller? Inside the pump,there is a part called the cam. It can wear down. How much wear/scoring inside the pump? If the cover has grooves in it it can cause it to cavitate and not pump?? If you've picked up a lot of sand it can ruin the housing of the pump. You in fresh water or salt? If the circ. pump isn't wobbling the chance it's bad is very small. Since it's overheating on one side that indicates that it's not getting enough water=impeller,risers,sand? It's a 96= 17 years old.It's probably past time for risers/manifold. Pofile? Location? You might be close to someone who can help???
 
Yes, impeller is perfect. Cam looks fine. Its very tight in there. Brand new manifolds and risers...I replaced them last month. Its a new boat to me. Im sure it was in Salt in the past..

I was under the impression that if the circulating pump wobbles that would be the bearings....but the fins could still be gone and that would be an issue...correct?

Im heading out Saturday to check the pump and then look for any suction of air into the line.

Im located in So CA, specifically the Inland Empire. Thank you
 
Update:

I swapped out the circulating pump with a new one...no change. Still overheats only while idleing

I sprayed shaving cream all over the water fitting and sucked through with a shop vac...looked fine. I even reversed the airflow to blow through and taped up the outdrive openings to see if I could hear a wistle....it just blew the tape off.

So, still no luck....

Anyone else have advice or things to look for?
 
Do you keep the boat on a trailer or in the water? If in the water, there could be marine growth inside the water intake grid in the outdrive, or the grids could be partially clogged.

If the engine is raw water cooled, have you checked the condition of the thermostat housing?
 
The boat sat on a trailer not running for 3-4 years. I bought it in November and have been going through it...no marine growth... I did take off the thermostat housing....looks fine.

The one thing I cannot identify is a box/resevoir above the rear of the engine...that the gas lines go into on top and below it has water lines feeding into it..... I think this is the one thing I cant take off (easily) and check out....what is this? Anyone know?
 
el_pescador said:
If in the water, there could be marine growth inside the water intake grid in the outdrive, or the grids could be partially clogged.

If the engine is raw water cooled, have you checked the condition of the thermostat housing?
Click to expand...
Ditto Eduardo on this one.
I've removed quite a few crustaceans from these areas, and these can be tough to clear out.

Also, if there is a Power Assist steering oil cooler, pull the suction hose and look inside for marine growth.

As a long shot here, remove your sea water pump impeller, and double check the impeller "depth" against the pump body cavity depth.
A correct impeller should sit just a bit "proud" of the housing when installed.
If it does not sit proud, it may be an incorrect impeller for that particular pump.



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I was told it was always trailered. I havent found any marine growth anywhere on this boat.

By proud do you mean edge to edge? I will double check it again, but....... I still think there must be something else... That brand new impeller was in there firm.
 
"Proud" meaning that when the impeller is installed, it won't be perfectly flush with the face of the pump body. It should protrude past the cavity by a few thousandths..... likely .010" +/-, or so. This creates a seal at either of the two thrust surfaces.


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Ok I think we fixed it. My brother has been taking off all the hoses one by one and checking them.... He got to the hose that went to the oil cooler and he said it was blocked with a "white crusty substance". He cleaned it out and then I got there....we ran it for 40 minutes and it stayed 160 the whole time. It never made it past 20 minutes before....

Thank you all for all the advice. Its been TRUELY appreciated.

Travis
 
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