Flow of raw water through motor

8122pbrainard wrote: TRBenj wrote: Exhaust manifold inlets are always lower than the thermostat housing, why would that matter? I made no reference to exhaust manifolds. The effluent of the engine's water jackets (at the front of the intake manifold, via the "marine conversion" casting) is lower than the sensor. That could leave a "pocket" above the coolant -- where the sensor resides. I really don't think this is our problem. But that area does exhibit very low temperatures when engine has been run on lengthy cruises. I feel Grant should go talk to this gentleman for more information: GMacLaren wrote: But a fellow here who owned a big boat dealership showed me how if there is no water around the sensor, readings are low -- this was confirmed with hand-held infrared thermometer. He must know more about it that we do?? Maybe big boats are different?

A "big boat dealership" was poorly stated. I should have written "a big dealership" --   

GMacLaren wrote: I made no mention of a "big boat,"

GMacLaren wrote: But a fellow here who owned a big boat dealership

Sorry Grant but now I'm really confused!!

To your knowledge Grant has this engine ever run at an acceptable temp? Does anyone else have the same conversion using the exact same parts? Is it possible,like the HM's,that they never ran any higher and when PCM bought them it wasn't for their superior cooling system design and they quit using it?

Gary S wrote: To your knowledge Grant 1) has this engine ever run at an acceptable temp? 2) Does anyone else have the same conversion using the exact same parts? 3) Is it possible,like the HM's,that they never ran any higher and when PCM bought them it wasn't for their superior cooling system design and they quit using it?

Gary,
1) Not to my knowledge. I ran it a few hours before discovering the cracked block. I do remember thinking the gauge was broken. I've changed all the gauges except fuel level. Sensor is correct for new gauge.

2) I don't know. I've been told by "CC experts" on recent St. Johns River trip that manifolds are "original." It's a '72 and they look different than the '73s in the 73 manual here on CCF.

3) In my opinion, it's a terrible design. I am wondering how lake water temp. will affect engine temps.

I've made all new gaskets for exhaust manifolds today. (3rd time a charm?) We are going to try restricting flow on "side jackets" tomorrow a.m. This should force some water into 'stat housing, and into upper ex. man. jackets. At idle now, top of ex manifolds reach 250F before we shut it down. I've not noticed this at higher RPMs, Tests show NO water in/out of top jackets at idle, up to 2500 in driveway. And the stat has NEVER opened -- except on my kitchen stove top.

We have tested every component of the system. We found that (intentional) 100% restriction of "side jackets" bring temp to 200F within one minute, but "top jackets" are cooled by water leaving pressure relief valve. With same 100% restriction, and drain petcocks open, it take about twice as long to reach 200F. So, we know restricting side flow does increase top flow and increases engine temp. Now, it will be "how much?"

Not yet mentioned in THIS thread -- I installed a "leakless" thru-hull fitting for prop shaft. It requires some cooling water -- which I picked it up from tranny fittting. It does seem to me that MORE raw water would improve my situation.

One of these four passages was blocked up a bit -- but not much:

Some results of today’s efforts to improve operating temperatures in MacSkier:

As expected, restricting water flow through the side jackets (the "lower loop") on the exhaust caps greatly improved water flow through the thermostat housing (and upper jacket in exhaust manifold), but still not enough to increase temperatures enough to open the 160F thermostat. All the improved flow occurred through the so-called pressure relief valve.

We now know that the flow should be restricted more here, but not restricted as much as by only opening petcocks — optimum restriction is somewhere between the two. (I’m tired of making gaskets — the material is “3 ply” with center ply metal — not easy to cut.)

See photos below showing,
1) the aft exhaust manifold cap with no gasket and
2) the same photo painted with blue — blue representing the shape of the gasket used to restrict flow today.





Improvements noted were 1) tops of exhaust manifolds today measured at 200F, whereas before restricted flow, the temps were 250F or higher, and 2) there was heated water in the “return” hoses in the lower loop.

We also noticed more even flow between the two exhaust pipes. (Before restriction more flow out starboard than port.)

We are now sure that more restriction would get the temperature gauge to read more desirable temperatures, but
1) the boat is to be run during a show on April 14, and
2) we will wait for higher lake water temperatures to observe how higher temps affect engine temps.
(My suspicion is high lake water temperatures will still not cause thermostat to open, and therefore engine temps will be too low for optimum engine performance and/or life.)

TRBenj wrote: Lake water temps will affect warm up time but not the running temperature (if everything else is proper). 160 is also the incorrect stat.

Good to know that. That's what is expected, and what we are trying to obtain. But we are still not getting enough warm water into thermostat housing.

In the current situation, lake water temp WILL affect operating temps.
We can demonstrate this by increasing water temp in bucket during driveway runs.

Is the "correct stat" a secret? Many have suggested 140, but since we have yet to attain much over 110 (on the boat's gauge), it makes little difference at this time.
Thermostat housing temp -- (top exterior) -- has yet to reach 100.

TRBenj wrote: Try pointing the thermometer to the water jacket on the intake (next to the temp sensor).

That's usually the first place we measure. It agrees with, or is a bit lower than, the boat's gauge -- as it should be. We measure all over!
And yes, that upper part is plastic. I wish it wasn't. Are metal castings available?

TRBenj wrote: Sounds like you've already received plenty of feedback on the 143 being the correct stat. Has to be a pretty poorly kept secret.

If/when we get more warm water up there, we'll get a lower temp stat.

I plan to run the boat up the Mississippi tomorrow -- dodging all the usual Flotsam and jetsam as I go.

In the driveway, with clamped board preventing prop shaft from turning in neutral and ruining cutlass

8122pbrainard wrote: Get your trans rebuilt.

Good idea. And them move engine, prop, drive shaft, thru-hull, rebuilt trans and new "closed" cooling system to my new boat. On second thought, I'll wait 'til trans fluid warms up.

Just wet the cutlass before starting & let the prop spin.

Read all the words Pete. He didn't say he was moving the engine in his boat. He said he would move them to another boat.