2000 5.7 gsi pwtr repower overheat help

[SD2600]

so today I had a planned fishing trip.. drop the boat in fire it up with a bump of the key and all is well.. I start to motor out just in gear.. maybe 5 knots and I see the temp climb... gets a lil got so I shut it down and drop anchor

while it’s cooling down I pull the brand new impeller.. looks great.. no leaks. Good o ring.. and the new bearing spins.. the housing is also new and free of grooves..

i fire it back up and the temp climbs at idle so I shut it down and call a tow...

back at the house I replace the thermostat o ring and gasket.. I also pull the drive and inspect the hose and plastic fitting that the h20 is pulled from...

i pulled the intake hose to the impeller and back flowed with a hose and water flowed out the drive.

With the hoses off the manifolds I start it on the hose... a few min pass and h20 flows out both hoses.. I shut it down. Connected the hoses to the manifolds and fired it...

ran for 25 min at idle on the hose and the temp is solid at 170

take it back to the bay and before I can get it to the dock the temp climbs.. I shut it down.. wait 5 min fire it up give it a lil neutral rev and the temp settles at 170... I say what the hell take it out if the no wake zone and get it on plane.. after 3-4 min I drop back to neutral... temp imidiately climbs... I shut it down and call a tow

i didn’t shoot it with a temp gun but both risers are hot to touch..

frustrated, defeated... but happy I made it home safe and got to give my two boys a bubble bath tonight..

2000 5.7 gsi pwtr. Sx-m 1:43

any idea where to go from hear????

 

[Scott Danforth]

did you change impeller yet? if not, do so the one could look fine, however not be fine. should be no curl to the vanes
if your impeller is missing vanes, then you need to fine them

check for blockage in the PS cooler

 

[SD2600]

The impeller is brand new... all of the vanes when it it pulled from the housing resemble a star with no curls..

i have not checked the ps cooler I’ll look at that

also any cons to running without my thermostat? This would insure water flo to my mani and risers....

thankyou for your reply

 

[SD2600]

Ok,pulled the ps cooler, unit itself is clean.

i flowed h20 from the hose on the port side and it flows cleanly out the out drive

flowed water from the starboard side and it flows clean out of the intake hose that connects to the impeller housing.

Just to confirm my impeller hose placement when looking directly at the impeller housing I have two connections, the lower one being closer to the 6 o’clock position and the upper closer to the nine o’clock... my intake connects to the 6 o’clock and the hose that runs to the thermostat housing connects to the 9...

any negative effects if i run it without a thermostat?

 

[SD2600]

Correction to the previous....intake 9 o’clock thermostat 6 o’clock

 

[SD2600]

ok. i think i resolved my problem. i believe i was pulling air at the intake housing. i replaced the pully/housing and immediately was getting good h20 out my outdrive. I pulled the thermostat and the temp would climb a hair above 175 on my gauge which i believe read 10 degree hot. when i would increase the throttle in neutral the temp would fall. all of these test were on the muffs.

I currently have the 160 deg thermostat out. is there any concern if i run without it? I live in san diego and use the boat during the summer to fish if that matters.

 

[Bondo]

I currently have the 160 deg thermostat out. is there any concern if i run without it? I live in san diego and use the boat during the summer to fish if that matters.

Ayuh,..... The t-stat directs water flow,.....

Water flows will change without it,.....

Boat motor coolin' systems are a balancin' act, which is why We use gaskets with little holes, where there's huge holes in the castin's bein' mated,....

It's Yer boat, so do as ya please, but unless doin' diagnostic testin', the motors I work on have t-stats in the t-stat housin's,.....

 

[SD2600]

Thanx for the reply, I think runnin a stat is the way to go..

 

[SD2600]

So I’m currently on the water still having overheat issues

I have the new thermostat installed
from the trailer to the dock and out of the no wake zone temp stayed at 175

i get on plane and cruising at 3300 rpm and the temp climbs to about 200

i pulled both hoses that supply the manifolds and fired the engine and I’m gettin water out of both

i bring it back to idle and rev in neutral to 1800 rpm for a moment and the temp falls to 175... I sit at idle for 5-10 min and it stays put

i attempt to get on plane at 3-3400 rpm and the temp climbs to 200 again

my lazer temp guage says 126 deg at the thermostat housing. Port riser is 127 starboard is 177

my starboard riser has always ran hotter but not hot enough that you can’t touch it

could my starboard manifold and riser be the problem?

 

[Bondo]

my lazer temp guage says 126 deg at the thermostat housing.

Ayuh,..... Sounds like the temp gauge is the problem,......

Exhaust manifolds are never, ever the same temps,.....

 

[SD2600]

so i replaced the starboard manifold and exhaust while i was on the water... the temp from the laser temp guage read lower about 165 give or take.... but the symptoms remained... idle at 175... when under way at about 2800 rpm + the temp would climb.

I motored back to the trailer... when i got home i installed a new temporary temp gauge.. positive and neg with alligator clips to the batt and the signal wire from the new temp sender to the new guage.. on the muffs the temp would climb to 180 at idle but with a lil neutral throttle it would lower to 160...

Tomorrow I plan for yet another sea trial under load and see what the new gauge reads... hopefully it doesn't get to hot and i found my culprit stand by for updates!

 

[SD2600]

well pretty much the same result. when i dropped it in the h20 is slowly warmed up to 160... idled out of the no wake zone and gave it some throttle to 3100 rpm.. temp increased to 180-190... i when back to neutral and the temp fell to 160

tried this about 7 times. anything over 2500 rpm and the temp climbed.

the new guage had its own new signal wire as well as using the boats wiring ... exact same results.

Thermostat housing was 132 when temp climbed. port riser 130 and starboard reached 172.

any ideas?

 

[Bondo]

Thermostat housing was 132 when temp climbed. port riser 130 and starboard reached 172.

Ayuh,.... Then change the sender,......

You don't have an overheat problem at those temps,.....

 

[SD2600]

thanks for the reply bondo, those temps were with the new sender that came with the new guage... i agree those temps would suggest im not overheating but the last think i want to do is blow up my brand-new motor

 

[kingsfisherman]

SD2600,

I have the 1998 BY version of the 5.7GSi with half system closed cooling and have recently been experiencing the same thing, have changed risers,manifolds,impeller,t-stat,pressure cap on H/E, H/E end cap gaskets. If you figure out the cause I would like to hear about it.

 

[SD2600]

Kings when I figure it out I will absolutely post my finding..

i plane Ane to gather some clear hoses for the impeller housing to check for air

I also need to remove the access panel on my sx-m outdrive to the shift linkage, there is an access panel that I have heard has a gasket.. this area is out of the h20 on plane and may be sucking air

ill keep u posted

 

[Horigan]

SD2600,

I have the 1998 BY version of the 5.7GSi with half system closed cooling and have recently been experiencing the same thing, have changed risers,manifolds,impeller,t-stat,pressure cap on H/E, H/E end cap gaskets. If you figure out the cause I would like to hear about it.

With a half closed system I would clean the heat exchanger. I had similar behavior and found the exchanger partially clogged. Note that the water flows back and fourth a few times before exiting, not just a single pass. I ran rods though each fresh water passage, then ran 50% muriatic acid solution though it with a spare bilge pump, hoses, and a bucket for 10 minutes. My temps are now rock solid at 160F. Google cleaning marine heat exchangers for some videos.

SD2600. Is the thermostat housing temperature with the IR varying with load/rpm, or is it always around 132F? Can you get a reading at the temp sensor? Maybe confirm your IR gun is calibrated by measuring a pot of boiled water. If the IR gun is good and showing stable temps at the T-stat and sender at 132F, then it could be a bad sender. Weird that it varies with load/rpm though.

 

[Lou C]

Google Volvo Penta overheat diagnosis and do the clear hose test to see if you are sucking in air on plane..since that’s when you overheat...possible causes plastic fitting in the pivot housing/transom mount and the impeller housing

 

[SD2600]

Horigan, the temp sender is about 7 inches from the thermostat housing... the sender itself is covered by hoses comping off the thermostat housing.. I’ll check the boiling water to ir gun.

I currently have a new temp guage and the temp sender it came with installed.. when my guage reads 160 my ir reading at the stat housing is about 110.. when I get on plane and the guage reads 190 I shut it down and it climbs to around 132

lou I’m going to follow the volvopenta overheat protocol with the clear hoses to try to locate my problem... I’m also going to check the access plate next to the shift linkage on my drive...

ill report my findings.. I should have a few hrs to tinker tomorrow am..

thankyou all for your input... hopefully Home Depot has the proper clear hose id and barbs...

 

[Lou C]

I have found the most accurate place to takes reading is the intake manifold right under the thermostat housing. Usually 10*F less than the temp gauge.