454 MAG OVERHEATING PROBLEM

[stingray230SX]

OK,here go's.....2000 454 MAG MPI--just turned over 100 hours,been running really great,including all day today,then stopped for a bite to eat at a place on the river for dinner,and when we took off again 1 hour later i had the first ever problem with this motor:
temp gauge shows 200(never been over 180 before)so i shut down and trim up drive to check for obstruction,finding nothing atthe lower unit intakes,trim down and restart only to have temp get even hotter,so again checking drive for clogging/check belt(serpetine)no abnormalities found,but restarting doesnt get the temps to go down,finally get the engine warning beep(kept it at idle while experimenting)(oil pressure good all this time)so shut down and called my buddy who had left the food place 5 minutes before me and got a tow back to my dock,only a short hop(3 or 4 hundred yards)
Once on the dock,he goes through the same steps i did,and when the gauge indicates 200 we fire it up again and it is missing and wont take any throttle,and smells way too rich at the exhaust,well its been dark while this is happening so we call it a nite.....
My thoughts are possible thermostat/impellor/?
anybody have any ideas? i will be checking it first thing in the morning so any replys before 8/9 AM would be great but am i doomed or what?
thanks
Douglas Hunt
[ August 29, 2003, 07:37 PM: Message edited by: stingray230SX ]

[Havasu Hangin']

When was the last time you changed the impeller?

[stingray230SX]

the impeller has not been changed yet(original still in there),i was hoping to change it when i winterized it at the end of september..
i had a short season last year(broke my leg)and with all the rain we have had i have only had it out maybe 8/9 times this year(thought the impeller service was due at 3 years)
doug
[ August 29, 2003, 08:54 PM: Message edited by: stingray230SX ]

[Havasu Hangin']

Just a thought- I would go by hours on the motor, rather than a specific calendar time period. 100 hours is up there...depending on usage. If you have sand in the water...it could shorten the life of the impeller (along with starting it dry).
I usually change mine every year- cheap insurance (a $20-$30 part) for not getting stranded.
Anyway...that would be the first thing I would check- you could be back on the water in an hour or so.
Next would be sand in the outdrive, or a thermostat. How was the water flow out the exhaust?

[stingray230SX]

its still in the water,on my slip,so i will have to look for another way to check for the water coming in......
water is not too sandy,more muddy after it rains but i usually dont run it when its real dirty/muddy anyway
the thermostat is also original,so im thinking get an impeller kit and a thermostat and gasket first thing in the morning check for water flow/if low/non exisistant,then trailer up and change the impeller....
is there a hose i can pull in the engine compartment to check for water flow from the outdrive?
thanks for your help already,i appreciate(sp) it!!
"How was the water flow out the exhaust?"
when you ask this question,is it thermostat related? or impeller related?,i will try to check it in the am for the water flow out the exhaust outlets before i put back on the trailer
doug
[ August 29, 2003, 09:21 PM: Message edited by: stingray230SX ]

[Havasu Hangin']

stingray230SX:
...is there a hose i can pull in the engine compartment to check for water flow from the outdrive? If your boat is still in the water, don't pull any hoses...you'll find out real quick if they are below the waterline.
stingray230SX:
when you ask this question,is it thermostat related? or impeller related?,i will try to check it in the am for the water flow out the exhaust outlets before i put back on the trailer..If the impeller is going south, you can usually tell by decreased water flow at idle (might even be more steam) coming out the exhaust. Of course, you'll need to have noticed how much flow you had before.
A thermostat going south won't change the flow much, as the water still has to get out, it just recirculates more first.
When it's on the trailer, pull the hose off the seawater pump and look for crap in there. Also, look inside the intake on the outdrive.
Have you ever started it dry?
I'll bet a beer it's the impeller...I'd change it anyway. When you get the old one out, look for broken or cracked veins. If any are missing, try to get them out- they may not have gone into the block yet.

[stingray230SX]

ok,no hose removal then,i kinda wondered about that after i typed it up,but its 12:43am here and i had been on the river since 12:00 noon...
ya know i DID notice a lot more steam out the exhaust while i was running it today,never really put that together until you mentioned it...
damn,if ya wasnt all the way across the country,id buy ya a bunch a beers!!!!!
and no,i have NEVER run any of my boats dry,always use the muffs and keep it at idle too...
thanks again
doug

[Havasu Hangin']

stingray230SX:
ya know i DID notice a lot more steam out the exhaust while i was running it today,never really put that together until you mentioned it...Yeah...less water flow means the exhaust gets hotter...less water also means it evaporates faster. I'm not an expert...but if it were me, I'd go straight to the impeller first.
stingray230SX:
damn,if ya wasnt all the way across the country,id buy ya a bunch a beers!!!!!Don't thank me yet!
Check it out tomorrow (or today), and let us know how it turns out.

[stingray230SX]

PROBLEM FOUND!!! it WAS the impeller that had decided to disintegrate.Sorry about the delay,but its our Sternwheel regatta and ive been on the river a lot.
went ahead and replaced it while on the slip,(just had to be careful to get that inlet hose up above the waterline quickly)
it was raining on saturday,but it let up enough for us to remove the pump and replace the impeller and housing(plastic thing)
ran fine after putting it back together(ran it for 30 miutes or so ,cruising around in the rain)our annual regatta is going on so there were some things going on bankside that we could check out,really just an excuse to get off the slip and run it!!
during that 30 minute run,it ran at the same temp it always had before--about 178 on the gauge--
part throttle/wide open etc,etc, it was the same.
Today ,however was a different story,as all day long during cruising/sitting/rafting up-whatever,it ran at --160--on the gauge,i wasnt sure why,but everthing else was in the green so i ran it ,keeping an eye on the temp gauge constantly.after putting around the regatta sections for a while,i took a couple of people for a ride(kinda fast)it went to its normal --178-- and stayed there until i shut it off,then we parked.After rafting up for the evening to wait on the fireworks,it sat for a few hours and upon startup and cruise home(about 10 minutes cruise)the temp went up to about --195-- and stayed there.i didnt like running it so i just took it real easy,but still wanted to make the slip without another tow!!it never went higher than that,and stayed that same needle position at idle during docking,but something isnt quite right and i am concerned,in fact i will attempt some test running tomorrow,but if it goes to 195 its going on the trailer,which sucks cause tomorrow is my last day till next thursday to boat...
Just guessing, i would say the rubber pieces from the impeller are playing havoc with my cooling system,or my thermostat(i bought that too,but havent installed it yet) is getting wonky.
thanks again havasu hangin' ,for your help
doug
[ August 31, 2003, 07:39 PM: Message edited by: stingray230SX ]

[Formula Dude]

Stingray
You needed to backflush when you replaced the impeller. The disentegrated impeller is now causing the high heat.

[stingray230SX]

thats what i figured,when looking at my bravo manual and seeing the path the water takes from the pump to the thermostat housing,i figure that one of the (3) inline coolers is getting partially blocked by the debris from the old impeller.
i am going to try to backflush from the powersteering cooler(its right below and to the right of the thermostat housing)while removing the output hose from the pump and use something to catch whatever comes out.
for what its worth,while testing it on monday,it never got over --180-- on the gauge,so its definatly something intermittatly blocking the flow of the water
doug
[ September 02, 2003, 06:43 AM: Message edited by: stingray230SX ]

[TCHB]

Yes you are on the right track. The rubber vanes that broke off are plugging up somewhere. I would like to put a clear filter on the outlet of the pump to catch all the debris if it happens again.

[stingray230SX]

the boat is on the trailer,under the carport where i keep it when i am not running it....
but i have not tried anything yet as work has kept me busy until after dark,but the river is high,swift,muddy etc so it does not matter :-(
i will probably try to backflush that cooling line all the way from the last hose before the thermostat back to the seawater pump on the weekend,since the weather and river is being uncooperative!!!!
thanks again for everyones help!!!!!
doug

[TCHB]

It sure seems like a lot of people are eating water pump impellers. I had a friend call me yesterday from Havasu and said he just ate a water pump impeller with less than one year in service. I wonder if the material being used has been changed.

[Dr. Eagle]

Those Mercruiser sea water pumps suck in my opinion. Guess it is better than having to pull the drive apart like in the alpha.
I guarantee that the impeller is kaput, and you probably also have little chunky bits of rubber in your oil cooler and maybe in your block. It would be a good idea to try to backflush the lines from the thermostat to the pump while it is apart.
You have to do them every other year at least, and Mercruiser suggests every year.
My twin big blocks ate their first impeller with only 55 hours and one season. The second went with about 90 hours and two seasons. I was lazy, had the parts but did not put them on. The pump crapped out first trip on the lake this season. I fixed it on the water with the tools I have on the boat. It is not really that hard to do yourself.
You cannot run the boat out of the water without being hooked up to a hose.

[stingray230SX]

WELL,i tried to backflush from the top hose(taken loose from the thermostat housing)at the top of the engine.The water flowed freely,but i didnt get any of the impellor debris from the hose at the pump.
I did this for at least 20 minutes,so yes,i am afraid that the rubber is farther in the cooling system.I have only run the boat once since the flushing attempt,and all was well(temp at an steady 179),but i am still concerned with where those impellor blade pieces are now.
should i disasemble further,as in pull the thermostat housing,or more?
getting ready to winterize,looks like the weather isnt going to give me any more nice weekends :-(
thanks again for everyones help
douglas hunt

[Dr. Eagle]

might want to peep down the oil cooler and see if something is caught in there, or in the hoses themselves. Beyond that, the thermostat housing would be the next step for sure. if it has made it into the block, I am not sure what can be done.
When mine disintegrated I got out major amounts of chunky bits from the oil cooler by backflushing it.

[stingray230SX]

well,i hated to do it but i went ahead and winterized the "ray" today.
water drained from all the block/cooler/manifold drains just fine,i KNOW that damn impeller pieces are in there somewhere,but at this point all i can do is keep my eye on that damn temp gauge all the time(next summer) :-(
thanks for everyones help,and to those still able to get on the water,go go go!!!!!!
doug

[Dr. Eagle]

stingray230SX:
well,i hated to do it but i went ahead and winterized the "ray" today.
water drained from all the block/cooler/manifold drains just fine,i KNOW that damn impeller pieces are in there somewhere,but at this point all i can do is keep my eye on that damn temp gauge all the time(next summer) :-(
thanks for everyones help,and to those still able to get on the water,go go go!!!!!!
doug Being in Northern California I think I have just about one more month before lay up for the winter. I am going to use it one or two more times before I mothball it for the winter. Hope you have no returning impeller gremlins next year!

[stingray230SX]

thanks doc!!! wish i could get a coupla more weekends in,but mothernature hasnt cooperated like i wanted.
there was two nice weekends since i did the layup but i had been tooo busy working to wait,the layup had to be done when i had the free time.
besides,nice is a relative term around these parts,cause on those two weekends no 'kinis woulda went out even though it was 75 or better
doug