GT-40 engine overheat

[richard]

My engine is GT-40,last time running on sea I notice the temp guage higher than normal,(go up 180-200F),so I stop the engine wait some time for cooler. later check raw water inlet, change raw pump impeller(the old one looks ok),I flush on land by pipe to the clean inlet,(the boat is 2001 Super Air Nautiqe)about, about 40 second,water firstcome out from prop shaft bearing and than exhaust out let,more water come out than exhaust outlet,I test to water,in low speed,few minutes later,I have a look at the guage,temp point 220F,and whole engine seems smoke and smelly,I turn off engine wait cooler and come back. *when run the boat in water,i notice water fired out from the cleaning water flush inlet,the pressure big even pop out the inlet cap away,the shoud no pressure. Any friend have advise ?

[skinautique]

RE: GT-40 engine overheat

Is your waterstrainer bowl cracked? Is there an Oring in there? Does the overheat occur at idle or faster speeds or both? Is the impeller flimsy? It could have all of the blades attached but the rubber is weak. I would replace it for piece of mind. Is water flowing freely from the hull pickup to the impeller pump? I hose won't tell the true test because the impeller doesn't need to work as hard. Have you checked all hose clamps to make sure they are snug?

[richard]

RE: GT-40 engine overheat

Join:
Kung Hei Fat Choi!
To day is second day of chinese new year,
water strainer had cleaned and o ring is there,overheat occur,at low speed ,impeller had cheange new by my self,raw pump test by tap water pipe have water comeout, I open the cover heat exchanger can see water flow,all the house join had checked and no leak,but all the test is done on land by water pipe,and seems ok,but when test to sea,drive in low speed ,around 1200-1500RPM,very fast go 220F,seem no cooling atall,collen tant is full, I'll check again 2-3 days later.
Thankyou for your opinion.

[skinautique]

RE: GT-40 engine overheat

check all of your hose clamps and did you install the new impeller properly? Was the old gasket cleaned off really well and you put the pump on in the right direction?

[todda]

RE: GT-40 engine overheat

Sounds rediculous, but I once had changed my impeller on my PCM and re-installed the impeller house upside down, so didn't pull water in. Maybe check it again just to make sure...?

[richard]

GT-40 engine overheat

possible fresh water circulation or thrmatate problem?

[richard]

RE: GT-40 engine overheat

Todda:
Kung Hei Fat Choi ?
The symtom is quite similer your case,when I take out the raw pump for changing impeller,I did'nt notice the direction, so I think quite a while when I put it back,I notice the impeller no direction for put,it's symatrical both side,the pump cannot put to bracket if reverse direction,so may be there are no mistake on this, how do you install upside down,could your tell more detail? Thank

[braibert]

Okay, So if it is not your impellar or strainer then you need to move on to the risers. We run our boats in salt water here, some with closed cooling some without.
About every 100-150 hours on the non-closed cooling systems you need to take off the riser and clean it out of debris, knock off loose rust etc. Upon re-install the mating surfaces have to be cleaned(wire brush wheel) and new gaskets installed.
And of course both the manifold and riser should be replace at about 500 hours and 5 years (or sooner??).

Good Luck,
Bob

[Nautiqueman]

I had a problem with an impeller once that disentegrated and then some of the rubber pieces became lodged before the impeller in the hose. I could not believe the parts became lodged in the intake hose BEFORE the impeller. Check that hose. This is the very same kind of diagnosis that I have had on my '93 SKI. Email if you like to my account. I have never been more frustrated than this experience because it was so simple to resolve, yet so difficult to find.

Hope all is well!

[richard]

Braibert:
I agree w/u,next time I'll remove the riser and check it if I don't have new idea. Thanks.

[richard]

Nautiqueman:
Thank you for share your experience,in fact,there are many reason make high temp,I still lost the way to find out the problem,I feel disy some times,but I think I can find the problem finally ,because I get many helps and idea here,here is realy a good place.

[Nautiqueman]

Richard,
Before I found the impeller pieces lodged in the hose BEFORE the water pump, I had replaced the filter bowl, temp guage, and the thermostat. All hoses need to be checked to see that NO air is getting into the system. A filter bowl crack that was not hardly visible caused air to be in my system and ran the heat up.

[richard]

What will I do

Nautiqueman :After hear many advise,I will try the following step
1: put the boat to water run the engine,to see have raw water come out from hose juntion w/heat exchanger or not.
2: check heat exchange in/out smooth or not,
3:take out riser to see have debries/rust or not,for do this, I have to get sealent/gasket first.

[richard]

mistake found

Today I checke the raw pump and found it install upside down,so water jet out from the flush inlet, after refixe it and try flush,quite good,water come out soon and plenty,(befre flush kit changed,impeller changed),main problem may be the flush kit air leak,I'll try to run to water next day,today is too late.

[ccole]

RE: mistake found

I took my 1994 Sport Nautique in to be winterized running fine in Oct 04, then picked it up in March 05 from the dealer dewinterized and with a new impeller. Put it in the water and let it idle, but as I hit the trottle the over heat light came on. Took it back and in the shop with a water hose on it wouldn't overheat, but in a water test it would. What they found was a piece of impeller about the size of a dime broke off and was lodged in the thermostat and there was a loose fitting letting air in. The result was that with the hose enough water was forced in to cool the engine, but on its own, the pump didn't have enough pressure to pull water in. After the clamp was tight, the piece removed, and a second new impeller put in (the new one showed wear from the overheat) it now runs fine. Just something to think about.