Overheating

[Flagman101]

Hello. I have read a bunch of other threads and cant find any definitive answer for myself.
So here is my situation.
I have recently, completly overhauled my engine.
Its a raw water cooled
No stones left unturned.
Block, head, manyfold were cleaned and are like new. No possible water restrictions.
I did a test run on the water last friday and the temp gauge was 200'.
Steam out of the exhaust.
There was water coming out.

I tested the thermostat in a 160' water bucket and it openned completly. Seems to be working fine.

I suspected either the thermostat is not working correctly because of a slightly corroded houssing cap. The spot where the thermostat is supposed to press against.
I assumed that a corroded housing cap would cause cooler temps, not hot.

During testing i tried and restrict de bypass hose with vise grips.
No change in temp. I find this puzzling.

I shut down the engine for 15 minutes and refired. Temps gauge was below 100, but started going up to 200 with the engine running. So gauge works.

When i bought the boat the original owner told me he had just replacde the muffler with a new one.
He also said the engine was overheating. I did not connect both togheter.
He removed the thermostat and the engine ran cool. 100.

So can a muffler make an engine overheat? How?
If by restricting the flow of the bypass hose i don not see any significant lower temps can i assume the probleme is after the thermostat?
Thanks for any help.

[MikeB.330]

Flagman,

Do you have good flow through the through hull valve?

If so, check to make sure the water pump is up to snuff. I assume that you replaced the impeller but what about the "shoe" inside the pump. If the shoe is worn, even a new impeller will not pump much water. A pump in good working order should suck up a gallon of water in short order. Try letting the pump pull water out of a bucket as a simple way to test the pump. If it takes more than 30 sec or so to empty the bucket you may have pump problem.

Mike

[Flagman101]

No i have not changed the shoe.
I will check for wear.
Like i said i will trouble shoot 101 the engine later this week.
I will start at the water intake and work my way up.
Thanks for the imput. The shoes is now on the trouble shooting list.
I did notice the engine was a bit slow to pump the water.

[Mark S]

Seems to me overheating engines are caused by (1) insufficient oil lubrication, or (2) insufficient coolant supply, or (3) a faulty water pump, or (4) a faulty thermostat, or (5) restricted waterways in the block, or (6) a restricted exhaust. I suggest starting with the easy ones, like checking the oil, then observing the engine take water from a bucket, then removing the thermostat, then . . .

Mark S

[Flagman101]

Oil is perfect. About 20 minutes old. 50 psi pressure
Water ways in the block are now perfectly open.
Very very intensive cleaning was done to the block and manifold.
It was a mess. My engine had the equivalent of high cholesterol.

I Cleaned the exhaust. It had a bit of silt in it but its now perfectly clean. Almost like knew.


Will do the trouble shooting 101 like you suggest. Thanks.
At least sails are working great !!

[luvmyi36]

Oil is perfect. About 20 minutes old. 50 psi pressure
Water ways in the block are now perfectly open.
Very very intensive cleaning was done to the block and manifold.
It was a mess. My engine had the equivalent of high cholesterol.

I Cleaned the exhaust. It had a bit of silt in it but its now perfectly clean. Almost like knew.


Will do the trouble shooting 101 like you suggest. Thanks.
At least sails are working great !!

Is it possible that there is an area that the cleaning did not take place in the block? Something maybe break loose and clog an all important passage? Just thinking aloud here....

[Flagman101]

Is it possible that there is an area that the cleaning did not take place in the block? Something maybe break loose and clog an all important passage? Just thinking aloud here....

Its always possible but i have put alot of effort in the cleaning.
The block was professionaly cleaned buy a machine shop. Twice.
The head and manyfold by me also twice.

[Dave Neptune]

Overheating Pt 1

Flagman, a good place to make your first "inspection" is to start at the other end!! A common place to build up a restriction and or to get crap stuck is at the water exit on the exhaust manifold. Remove the hose, then remove the fitting and inspect and poke around with a piece of wire. This is the first spot to check as the water can't flow in unless it can flow out.
Then look at the thermostat situation and try restricting the bypass when you KNOW the exit is clear!!!

Dave Neptune

[Marian Claire]

When I rebuilt my A 4 last year I had the head and block “boiled”. They can not use the really nasty stuff, thank goodness, they used to use. I cleaned the manifold. Then I used my grading contractors pressure washer, this is not the one you get at Lowes, this thing is as big as a VW. Scalding hot and high PSI. I was amazed at what came out of the “clean parts”. I have posted about my thermostat problems and using a ball valve to control the flow and therefore the temp. Has worked just fine so far, 2100 miles and counting. Dan S/V Marian Claire

[Dromo]

thermostat

Daniel, I would remove the thermostat. Run the engine and see if make a difference. Checking the thermostat in hot water to see if it opens isn't a sure sign that it is working properly. With your engines history of over heating I would concentrate in that area first.
If that doesn't not work.
Before putting the thermostat back in , I would run a hose from the water exiting of the manifold overboard or into your sink if you have a gray water set up { sink drains over board, not into a holding tank}. If that works ,install the thermostat and repeat the test, If the temp. is OK, then the problem is down stream from the engine.
good luck Rick

[Flagman101]

I think i have resolved the problem.
The prvious honer had ordered a thermostat from Moyer. He proudly showed me the invoice.
However this thermostat is a conversion thermostat not the OEM.
If i'm not mistaking the conversion thermostat needs to be installed using the spacer in the conversion kit.
This was not ordered and installed. So there is no way to fit the thermostat other then upside down.
By doing this the thermostat can't create a restriction on the bypass. So the water goes the easy way out.
By putting a restriction manually on the bypass hose the water unded up traped in the engine by the thermostat and could not flow out by the bypass.
So my temps kept going up until the thermostat opened enough for the water in the block to flow out.
That is what was causing my temp gauge to go up and down.
So i'm going to order the spacer and installe the thermostat the correct was. Tail up.
Should fix the probleme.
I already have the longer studs installed on the block. So its a 15 minutes job.

[Flagman101]

Wich way does the thermostat go. I still have overheating and i'm sure its because of the thermostat.
If i put it with the sping up i get overheating. If i put it with spring down i get irregular temperature.
I have the conversion thermostat and the spacer.

[Kurt]

I thought it only went one way. It's been a while since I've worked on mine, but I believe the spring goes down - facing the head.

[P30_889]

The spring goes down.

The flat part should raise up and block off the water coming into the therm. housing if working properly.

[Flagman101]

When i put it like that i get irregular temperature. Overheating and some sudden drops.
So not knowing any better i try to turn it up side down. Does not fit.
So i figure its a conversion thermostat and order the spacer that was missing.
Installed wit sping up. Does'nt work.
I tryed it with a cheap car thermostat because it was a tight fit.
I will turn it aroing.
I wanted to do with out the restricting valve on the bypass hose but i guess i will have to install one.