Need help! Bad running 165hp Mercruiser

[rfishman47]

I have a 1977 century run about,it is powered by a 165hp inline six,mercruiser stern drive.I winterized the boat and it had been in storeage for 5 years.What it is happing.the motor starts up real easy and runs fine,till the engine heats up to around 150 degrees, Running it at about 2600 rpms,the lifter noise starts and is very loud.By coming back down to idle and letting it cool down for awhile you can take off and get back up in rpms and run till it heats back up and starts making noise again.Also it has a loud exhaust after it heats up,but seems to get lower after it cools.
What l've done= compression check,3 at 160 psi,one at 158 psi,one at 152 psi and no. 6 at about 135psi. I have rebuilt the carb since the boat sat so long all the gas had evaperated out of it.I pulled the pulgs and checked them which they are burning black,which would show a rich fuel condition.The enine oil is clean and seems to be ok.The exhaust manifold seems to be running cool enough,but the engine block seems to be alot hotter.I've run the boat at hagg lake for about 2hour run time and we just got back from a trip to the john day river where we put about 6 to 8 miles on the boat,having to run and slow down to cool it down so we could get to where we were going.I'm at witts end as to what the problem is short of tearing the head off to see what I can find.Is there anybody out there that can Help!!! Thanks to all, rfishman.

[Lou]

Did you by chance look at the thermistat?
Its been in there for a long time with no movement.
It could be stuck.:)

[rfishman47]

Thanks for the help Lou,I pulled the thermostat and found it to be stuck open.Would this be what is causing it to make all the lifter noise?Will replace it and then try it at the lake next week.Is there any thing else I should be looking at?

[Lou]

Thanks for the help Lou,I pulled the thermostat and found it to be stuck open.Would this be what is causing it to make all the lifter noise?Will replace it and then try it at the lake next week.Is there any thing else I should be looking at?
Might be the oil pump! Or low oil level.
Try matching the oil filter to a PureOne or simular type.
They don't allow the oil to run back in to the pan. Might be
a pluged oil line?
You might have to put an oil pressure gauge on.
The thermostat needs replacing if it is stuck.
Uou have an oil pressure problem:passout:.
Ask FishKisser for his input!

[fishkisser]

Might be a gummed up or sticking lifter you can buy oil additives that will help clean the gum and gunk out ... I would hope that it is not a worn lifter or cam problem another thing that happens is lifters stick in there bores and bend pushrods if the motor was not winterized properly when stored.... But these problems and noises ,stuck or collapsed lifters would be present at startup and decrease slightly or go away when warmed up or oil pressure restores the cushion in the lifter ...
I have also seen on the old I-6 motors , gunk build up in the passages in the head that allows oil to return to the sump/oil pan ... We use to run a coat hanger or piece of wire down them to open them up and allow oil flow, change the oil and put a pint or two of kerosene in and run till warm and change the oil and filter again ...
Another knocking noise that increase at normal engine temps while under load detonation /abnormal combustion ...

Detonation can be prevented by the use of a fuel with higher octane rating, enriching the fuel/air ratio, or reducing the load on the engine and appropriate calibration of the engine's ignition timing schedule ...
It would help if I knew what the manufacturer of the motor is ie. ford ,chevy and what year it is also how many hours on the motor and if it is cooled by raw water or is a sealed cooling system with a heat exchanger ...
I would hope you are not trying to run this motor on 5 year old gas either ...
Good Luck ...Barney:wave:

[Okie]

When you replace the thermostat, it could solve your problem as the lifter noise could go away with the increase in operating temperture. A cold runing engine can cause all kinds of problems. Oil circulations isn't the same when the engine is cold.

Good Luck