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57 overheatingout of options

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jasonb

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"Raw water cooled GM 350/280 d

"Raw water cooled GM 350/280 drive. Under a load, the temp runs about 190 at idle, and 200-220 at 3500-4500 rpm. When I shut the engine down, Its hot enough that the battery cant turn the starter over until a 30-45 min cool down, after which it fires right up (compression?). This tells me that the engine is pretty hot, as the guage will peg when I shut the engine off.

I have replaced the manifolds and risers, raw water pump, recirc pump, thermostat, temp guage, sending unit and also changed the gasket on the drive water neck. Batteries, starter, carb and alt are all brand new, along with all electrical connections, batt switch and battery cables.

The problem is, when the boat is on the trailer and the drive is submerged in a tub of water, the flow is strong. I disconnected the hose to the recirc pump and the flow is good and increases with rpm. I did a pressure test from the raw water pump back to the drive by taping up the drive inlet vents and that checked out good. I also pulled the heads, changed the head gaskets (they were in good shape) and replaced all the freeze plugs after flushing out the block (lots of sand/silt).

I am running out of options and was hoping someone had a few nuggets of wisdom to get me on the water.

Thanks in advance."
 
"Just a though here. Chevy 35

"Just a though here. Chevy 350's are bad for overheating the starter in auto applications, might this be happening to you? If you had a car that was doing this, I might suggest you change the starter or solenoid as they don't work well when hot and worn out."
 
what year 350 do you have?? ca

what year 350 do you have?? carb. or FI??? points or electronic ignition??? need alittle more info.
 
"What thermostat are you using

"What thermostat are you using. You should be running a cool one, my guess is around 145 degrees. What about the raw water inlet fitting on the outdrive, the one that tends to corrode?

Tell us what you find. Have a great day,

Rob."
 
"I HAVE A 350 VORTEC IN MY BOA

"I HAVE A 350 VORTEC IN MY BOAT, AND A 180 THERMOSTAT. MY TEMP RARELY GOES OVER 180, ONLY AT FAST SPEEDS IN THE DEAD OF SUMMER WHEN THE WATER TEMP IS HIGH LIKE 80"
 
"You might have problems with

"You might have problems with the thermostat housing, particularly if You have cleaned out the excit to the manifolds too well. You need an overpressure from the impeller pump to make the thermostat system and circulation system work properly, as well as a 'tight' circulation pump.(too much clearing between impeller 'wings' and housing reduces circulation ceverly).
1: Check out thermostat and housing.
2: Take down the rear place of the circulation pump and check space between impeller and housing. If impeller dammaged by cavitation, change the pump.

Normall difference in temp reading between idle and full should be about 20-30F.
A high idle reading might as well be resistance in cables/connectors etc between engine and instruments. Do a refference check with a 'clean' cable between instrument and temp sender."
 
"Thanks all for the responses.

"Thanks all for the responses.

I am running a 140 degree thermostat. I am going to pull the thermostat this afternoon and sea trial without it to see what my temps indicate.

More answers to your questions: The motor is carb'd with elec ignition. I just ran the block castings and its an "010" which is either a '67 327 or a '79-'87 350. The casting stamp on the front of the block references this motor as a 327 out of a '68 camaro???? The head castings say they are '71 307 heads (1.72 intakes, 72cc). When I had the heads off, the pistons were stamped ".090" which after thinking, is way too much for a marine engine. If the cylinder walls are too thin this might cause a hot engine. If the heads have been resurfaced more than once, my compression might be 10-11:1, also causing it to overheat and not start. The pistons are dished and ARE marine pistons according to visual comparison to other marine pistons.

Morten, the recirc pump is brand new but I will pull that back off and check the impeller.

The boat is an '81 22' Anacapri center console that has been completely refurb'd. I didn't build this motor as it came with the boat.

You guys are great. I really appreciate all your input."
 
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