thermostats

[hydrick]

at what temp would audible alarm go off for a 160 degree thermostat.i'm trying to do a process of elimination on my 98 454 mag.gauge reading 185-200 and alarm sounds.new sea water pump last year, no visible obstructions.i did find leaking hose at sea pump inlet, as well as a winterizing plug. oil pressure fine(at gauge)outdrive reservoir just a tad below full. my problem developed coming home from about a ten mile run.I'd go a few miles get the alarm,see temp at around 200(at gauge)cut engine off,restart, and gtemp would drop to about 150 slowly climbing back to around 180-200 on gauge,alarm would sound, and I'd do the same as before, stop,cut engine restart,and watch temp fall again to 150 restart go few miles and the same.thanks for any responsers,Ronnie

 

[thumpar]

The alarm goes off at a few degrees below 200. You have a cooling issue that needs to be fixed. When was the impeller replaced last?

 

[hydrick]

end of September last season.has gone approximately 2 hours since then

 

[redneck joe]

not a sterndrive? On my 1989 454's from US Marine I was able to put the impellers in backwards rotation and they did not flip as everyone told me they would.

When you replaced, did you have whole impellers or pieces and if pieces did you find all pieces?

 

[jaxnjil]

was the impeller because it failed?? would check flow from oil cooler line at thermostat housing and make sure you have good flow there and look for bits of rubber impeller. if so, flush cooler

also might check sea water belt and tension

2 hr on new BUT might have gotten run without water after winterized, or impeller stuck in housing over winter.

tore a vein or 2 at start up

 

[hydrick]

it was replaced because it failed.tech thought he'd found it all.so if it's a piece would it most likely make it through the power steering cooler?if so trapped at thermostat?i drained the petcocks everywhere and found nothing.

 

[Bondo]

it was replaced because it failed.tech thought he'd found it all.so if it's a piece would it most likely make it through the power steering cooler?if so trapped at thermostat?i drained the petcocks everywhere and found nothing.

Ayuh,... Impeller pieces usually get hung up in the P/S Cooler, Or the T-stat housin',...

Everybody's lookin' at the impeller,.... Water has to get Out of the motor too,... What conditions are the exhaust Risers,..??

 

[jaxnjil]

yes i have seen small bits of rubber make it through the cooler and make it to the thermostat housing.

since the thermostat housing is the first stop for sea water after the oil cooler you might not get any thing in the block or manifolds petcocks.

not sure if you pulling sea water through drive or sea ****. have see plastic bags, 6 pack plastic rings and paper plug or partly plug sea cocks.

can you look under boat and confirm thats clear?

would confirm sea water volume and circulation . asuming you have a raw water system.

 

[thumpar]

When mine when I took the hose off the thermostat housing and off the seawater pump. I shoved a garden hose in the hose at the thermostat and turned it on. Lots of pieces came out. After I knew that was good I took the thermostat housing off and checked it out.

 

[hydrick]

Ayuh,... Impeller pieces usually get hung up in the P/S Cooler, Or the T-stat housin',...

Everybody's lookin' at the impeller,.... Water has to get Out of the motor too,... What conditions are the exhaust Risers,..??

unsure of condition however engine has just a little over 200 hours and runs in fresh water when not in storage.

 

[hydrick]

update:found a blade in the rear of the power steering cooler.blew out all hoses except one leading from pump.was sure the problem was solved. got about 20 minutes out watching gauges that stayed 175-180 for about 18 of those minutes it then hits 200 and alarm sounds.shut engine off raised engine cover,and engine definitely hot.all hoses leading to thermostat were under extreme pressure.waited about 5 minutes cranked it and the temp came back into operating range.
sat awhile at the local hang out made it back home.pulled thermostat and water tested in hot water.thermostat didn't open till about 175,and it was an 1/8 of an inch opening (if that) once water temp hit 200, it was wide open.i'm hoping possibly a stcking thermostsat?might as well change it while out.
the blade I hope is left from the last worn out blade.

 

[hydrick]

update: back in july I replaced thermostat, found that it was wobbly at it's retainer point.put boat in ran for over an hour at around 30mph no problem.thought everything was fine.i decided to open her up and before top speed she was running over 200 degrees and alarm sounding off.idled down and it cooled immediately back into operating temp of about 170.
completely confused at this point I said the heck with it we'll replace them impeller again during the winter. waited till this weekend and decided to pull one more hose at the oil cooler and found 5 wadded up blades from LAST impeller repair.once I cleaned all that out i was able to once again enjoy my boat and do what it was designed for..........run fast without over heating.

 

[Bondo]

update: back in july I replaced thermostat, found that it was wobbly at it's retainer point.put boat in ran for over an hour at around 30mph no problem.thought everything was fine.i decided to open her up and before top speed she was running over 200 degrees and alarm sounding off.idled down and it cooled immediately back into operating temp of about 170.
completely confused at this point I said the heck with it we'll replace them impeller again during the winter. waited till this weekend and decided to pull one more hose at the oil cooler and found 5 wadded up blades from LAST impeller repair.once I cleaned all that out i was able to once again enjoy my boat and do what it was designed for..........run fast without over heating.

Ayuh,.... Glad ya found it,..... Good luck, now ya know where to look,....