More problems w 470 overheating

"OK guys after replaceing the

"OK guys after replaceing the impeller and houseing
it ran for about 45 min and started to overheat again I am at a loss on this problem any got some ideas i have replaced just about everthing i can
new hoses T stact ,4" heat exchanger r &r the maniflod and the pickup hose butween pump and transom.
looks good it ran about 160 for a while when slowed down to 5 mph it increase to about 190-200
then start going again it cools down to 160
then when i opened all the way for about a half mile it ingrease to 190 and wont cool down from their you have about five min to get back to the launch ramp before it get to 200-230 the water backs into the resivor is that normal the resivor
i feel it about a 1/4 full then it will fill it all the way up and when it finilly cools down in about 2 hrs thr go back into the engine from the resivor i need some more help

Thankyou everyone for the info but what eles can
cause this prioblem???????????
and my other question is when it runs about 190 before it get to 225 all the cooling hoses have so much presure you cant even squsse them and then itgoes beyond and cant bring the temp down blow head gasketr matbe but no water in oil or any leaksd????????"

"Compression test will rule ou

"Compression test will rule out a blown head gasket. What does the exhaust flapper look like? Restricted exhaust flow can cause an engine to overheat. Have you tested the overflow coolant tank pressure cap. It should release at about 16 PSI.

"r&r the manifold" Do you mean replaced it? If not, the old exhaust manifold, elbow and end plates need to be acid cleaned and rodded out to remove mineral and rust scale buildup over the years. Many 470 owners don't perform this service which is needed about every 300 hours under normal useage in fresh water and sooner in salt water.

Get a couple of gallons of muriatic acid; CAREFUL HERE, ACID BURNS ANYTHING BUT PLASTIC INCLUDING YOUR SKIN--USE A FACE SHIELD WORKING WITH IT AND ELBOW LENGTH RUBBER GLOVES AND APRON.
Soak the parts (cast iron only) for 1.5 hours, rinse with fresh water and then rod out the openings with a stiff brush. Rinse again and rod and rinse again."

Sounds like your exchanger is

Sounds like your exchanger is fouled. Have you cleaned it out either manually or with chemical?
Rod

Have not done a compression te

Have not done a compression test yet i pulled off the exhaust manifold and flush water through it i will get some muriatic acid and try that.

I just about hadit with this moter ijust cant figure it out yetthe heat exchanger i upgraded to 4" and the iside is clean and replaced the pressure cap also but it seems to build up so much pressure you cant squeeze the hoses when it is hot.

"Pressure cap correct one? Co

"Pressure cap correct one? Could be a bad one. Test it. Hoses should be tight under pressure which raises the boiling point of your coolant. BTY, are you using a 50/50 mix of antifreeze? Straight antifreeze will cause overheating and it will also freeze."

Ok I did a compression teat a

Ok I did a compression teat and the resuilt are
cyl 1 125
cyl 2 155
cyl 3 140
cyl 4 140
so i have a blown head gasket in which is causing
my over heating problem.

"Check the compression with a

"Check the compression with a tablespoon of oil in each cylinder and compare those readings with the dry readings. If compression increases, you need rings. When you pull the head, it is important that you check the block for trueness with a straightedge. Distortions on its surface caused by overheating could require milling. If you need rings and a head gasket, valve job,etc.; time for a total rebuild or consider a repower."

"If she has an alpha 1 drive,

"If she has an alpha 1 drive, try installing a clear plastic hose after your oil cooler and then to your thermostat housing. If you see bubbles you could be sucking exhaust. Had this problem only to find my lower gear housing was pitted where the 1/8 " pump gasket seats to the pump base"

"Just purchased 1980 Silverlin

"Just purchased 1980 Silverline inboard with a Mercruiser 260 hp V8. (Chevy).Test drove it for about 1 hr in river,ran great temp. at 160.Took it to lake yesterday for first time
did just fine,stopped for about couple of hrs to fish.While going back to dock (not at full speed) engine overheated to 240 and stopped running waited 'till engine cooled and finally made it to launch, engine again overheating,checked belts all intact at that point oil pressure was low. I used the garden hose today oil pressure back to normal,pulling water but don't know if its letting it out.Never owned a boat before have no idea where to start.Any suggestion greatly appreciated."

Welcome Pat:

It is customar

Welcome Pat:

It is customary to start a new posting for a new problem rather than tag onto another's so all can see it and you can get the most help. Thanks.

HI Guys

Still having probl

HI Guys

Still having problems with overheating
I check the timing thats goods recheck the impeller it was fine i am at a loss. I need some more help i dont know what else it would be.Im about ready to take to macanic any know a good in sacramento ca

Thanks Craig

Craig:

Timing is 4 deg. BT

Craig:

Timing is 4 deg. BTDC not 8 deg. as I said earlier. Are you using synthetic engine oil? It will help reduce operating temp. somewhat. Try Mobil 1 15W40 or 20W50. Your coolant mixture should be 50% automotive antifreeze (not winterizing type) and 50% distilled water.

Guy:
i reset the timing and i

Guy:
i reset the timing and it still gets hot it build
up some much preesure when it gets nhot blows the cap off of the resivior any more ideas

Thanks Craig

"Last one; remove the thermost

"Last one; remove the thermostat and see if it still overheats. If it does not over heat, it is your thermostat. Test the T'stat with a candy thermometer to see when it opens, if it does. Make sure you have the right one with the copper pellet installed down, not up."