Cooling System Issues...Help

[gstar]

In answer to the last post, the impellor is brand new, never been run dry or attached to a hose and I
checked it before I changed the thermostat and it was fine.

I just installed the 143 degree thermostat today and it has helped reduce the operating temps to between
140-160 depending on what I'm doing with the boat. At this point I'd say problem solved, but for the
fluctuation of 20 degrees, which I never noticed before. Is it normal to have some movement up and
down depending on speed, load etc.?

... And new problem today after I took two massive waves over the bow, the boat ran fine and the bilge pump emptied the water out quickly, but when I went to start it after sitting on the lift draining for a few minutes, it wouldn't start. Specifically, the blower was running but the starter didn't even make a clicking sound. Pure silence when you turn the key (except blower running).

I'll start a new post for this issue, but obviously something got wet that didn't like it. Any ideas?

[gstar]

Thought this issue was resolved and maybe this is normal, but I had the boat heat up to 220ish degrees while idling for
about 15 minutes. As soon as I started driving it went right down. Is this normal? I'm paranoid now that it overheated once.

[Blackntan90]

A couple of years ago I had my Mariah(351PCM) overheat from an impeller gone south- I had the same issues as you are describing-temp fluctuate 10-20 degrees. I took all of my hoses off looking for the blockage, finally I used compressed air to blow an impeller vane from deep inside a hose where I did not see it! Best of luck to you- let us know how it turns out!

[earl b]

I have a 1990 Mariah and just repaired a heating problem. I replaced the impeller and the thermostat and remove parts of the impeller from on top of the thermostat .Went to the lake an the temp was back to normal. After about a hour the temp when over 200 deg. When back to the house and took all the hoses loose and ran water threw each hose and transmission cooler no blockage. Took the raw water pump back out and the impeller was good.But the inlet to the raw water pump hosing was full of old impeller.You might check there. I still don't know how it got there since it is not a closed loop system. Hope this helps.

[devovino]

When I bought my Saltare, the PO told me that "if I wanted to get better MPG, to install a thermostat" which I assumed meant there is no thermostat on my 454. She runs like a champ, never had a propblem wih her heating up, in fact I assumed the only gauge not working on the Saltare was the temp gauge, then yesterday I had 7 people and 1000 lbs ballast on the boat was running around doing some surfing, temp never registered. But once I stopped to just float and listen to the radio, I noticed the temp gauge was registering ar 150, so I now see that it works, I think the engine is always really cooled from constant flow of water. In talking to a few mechanics, they think the only real problem with this is it might never really reach a good operating temperature, and maybe run rich,does anybody else see a real problem with a really coo engine, I figure better cool than too hot! Thanks Devon

[docdrs]

Check all your intake connections to make you have no places you could be sucking air. Check your impeller housing gaskets and cover plate screws so no possible air leaks

[DAFF]

I am wondering if the reason the first impeller went out was from lack of water. I have a fealing you should inspect the lines from the hull to the impeller. Check for obstructions, cracks, broken or missing hose clamps ect. Remove every hose and look through it.

Don't over look the strainer perhaps some seaweed or debris stuck in there.

[rludtke]

When I bought my Saltare, the PO told me that "if I wanted to get better MPG, to install a thermostat" which I assumed meant there is no thermostat on my 454. She runs like a champ, never had a propblem wih her heating up, in fact I assumed the only gauge not working on the Saltare was the temp gauge, then yesterday I had 7 people and 1000 lbs ballast on the boat was running around doing some surfing, temp never registered. But once I stopped to just float and listen to the radio, I noticed the temp gauge was registering ar 150, so I now see that it works, I think the engine is always really cooled from constant flow of water. In talking to a few mechanics, they think the only real problem with this is it might never really reach a good operating temperature, and maybe run rich,does anybody else see a real problem with a really coo engine, I figure better cool than too hot! Thanks Devon

Hi Devon,

Running under the design temp is almost as bad as excessive temperatures. The parts of the engine are sized to work at a certain operating temperature range. Below or above this range, the parts will be either to large or to small for the space that are placed to work in. The engine uses a lot of steel and aluminum parts in near proximity to each other (such as bearing surfaces of the crankshaft) neither of which expand or contract at the same rate when heated or cooled. Excessive clearances between moving parts, and/or inadequate clearances between moving parts will result in less than optimal performance, excessive wear or damage to your engine.

I recomend you install the correct thermostat for your engine (and replace it every several years), and confirm that you gauge is functioning correctly. A simple test for this is to remove the senser, and while connected to the wiring (with power and ignition switch on) place the sensor into boiling water, and observe the temperature gauge response. If the gauge indicates 212 degrees F (or thereabouts) you should feel confident that the gauge/sensor is functioning and is reasonably acuright.