over heating

maybe possibly go to a 140 thermostat, it sounds like its spiking due to the 160 therm.it maybe heating to 160, it opens then you get cold water back to it and it closes. the 140 may close the gap and regulate the flow consistantly. this was my first thought.....just an idea. by the way welcome to the site! Eric

the old interceptors have some tricks to them, uneven T's that need to face a particular direction thermostat bypa$$es that should or shouldnt be there etc, Take a picture if you can of your current routings and components.
-Joe.

We need some pics. Have you checked the circ pump? When I changed mine years ago, the blades were gone, worn off, it wasn't pushing water at all. What style of thermostat did you get? I've noticed that the one on the right below works better. I would go with a 140 or 142 degree stat.

Olebots,had a 302 that no amout of money could cool down,PO thru money at it from pumps ,raw water and circulating,thermostats in and out. Reworked the heads, possible cracks,fixed the problem,SOLD THE BOAT.
My buddy bought the problem,along with all the old parts,his fix was to change the entire motor,boat ran cool..........
I end up with the complete motor,manifolds,pump,risers,etc.Sets in my shop for a year,no time nor desire to chase rabbits on that old a motor.
On day while walking past looked inside the port riser,there was no hole or channel at the top for the dump,rust and sediment plugged the channel,a set of risers fixed the overheat problem.
check the flow at the manifolds .this is how the engine purges the hot water.My .02 worth
..............boat dr

OK, you've got the same set up as my mustang, except for the pvc pipe. You need to check the bypa$$ hose that goes from the circ pump to the intake manifold to the left of the distributor. Take that hose off, pull off the thermostat cover and check to see if the 90 degree fitting is clogged. Push some wire or something to make sure it's not clogged. I found impellor blades in that fitting twice after my impellor pump shredded 2 years ago. Also verify that when you turn the circ pump pulley, the water blades on the pump are turning. Here's a pic of my '66.

What do you mean by "larger line should feed the t-stat"?

The "T" which has a small outlet and a larger outlet (red arrow) does not cool the engine. It supplies the exhaust manifolds a constant flow of water.

Let me get this right, you think water enters the motor at the thermostat?

"there's only one hose on the output side of the RWP and it flows into the TEE without and branchs correct?"

If thats the case then that is a problem, he should have two lines coming off the RWP, one that goes to that T up top, and one that goes to the large inlet of the Circulating pump. The circulating pump needs to increase the pressure of the water inside the block to a level higher than that of the RWP so that when the thermostat opens it allows the hot water to be pushed out of the engine (against the pressure of the RWP that is being provided to the manifolds.) There is also a bypa$$ from the manifold down to another inlet on the circulating pump that keeps the water in the engine moving.

Its not the best system ever devised. Even with the special T that restricts flow on the port side so some water will make it over to the starboard size its hard to keep the two sides the same temp. It is imperative with this setup that your thermostat has a pretty low pressure drop, similar to the one on the right, or the pressure from the RWP can prevent the hot water from making it out.


If you are missing impellor blades on one of these interceptor type setups they are most likely in the caps on the front of the manifolds they have a relatively large intlet but then channel the flow of the water into the small jackets around the manifolds, I have had a couple sets of these manifolds and found old broken impellor blades in both at this spot.

I have changed my routing at this point and it works great, even temps on both manifolds, temp is always rock solid on the engine but its real ugly....
-Joe.

so then the output to the RWP then Tee's to feed the circ pump and exhaust, and on the exhaust leg from that it tee's again to feed both ex manifolds. ok. The other systems seems a little easier with the different style t-stat housing and circ pump compair to this set up.


Seems like there's nothing that can be done to keep them equal the drivers side is always going to be hotter. Sure glade I've got the other style fewer hoses and connections.

Yes mine has the "bypa$$" hose from the intake to the circ pump. On the circ pump, one of the fittings has a rubber plug, I think you can barely see it above the pulley in that last photo. My circ pump is fairly new, one of those rt. hand only models from ski dim. Do you have sufficient water flow? Can you run it on a fake-a-lake? There is a cam plate in the bottom of the rwp that can be replaced, its on the bottom where the pump pulls water across the holes.

79nautique wrote: so then the output to the RWP then Tee's to feed the circ pump and exhaust, and on the exhaust leg from that it tee's again to feed both ex manifolds. ok. The other systems seems a little easier with the different style t-stat housing and circ pump compair to this set up. Seems like there's nothing that can be done to keep them equal the drivers side is always going to be hotter. Sure glade I've got the other style fewer hoses and connections.

Me too.... You guys with these motors really do need to watch your gauges and impellers.. To many darn hoses

Moj'