SN2001 Overheats with T stat but runs cool without

1. Does it make sense to remove the manifolds for cleaning?
2. Can I blow out a portion of the engine with the manifolds removed or do I need to go deep to find a potential clog?

Hollywood - I hope you are right. I'll report back tomorrow.

UndercoverPoe wrote: So here is Today/Yesterday Update: 8. I don't have a temp gun yet - but I felt around for the hot section.   THe section that I felt that was HOT HOT HOT was after the t-stat housing - the large metal housing/outlet tube going down - with markings 'R020500" was HOT!.

Go buy a IR temp gun then define HOT HOT HOT
Mine runs mid 140's and you can not hold onto that outlet tube either

I think 13 gpm at 1500 rpm

That big line is the suction to the circulating pump from the thermostat housing and is the temperature of the water going into the block. It's gonna be pretty hot after the boat is all warmed up and at operating temperature

From there it goes through the block and comes out the front of the intake manifold to the thermostat housing again at a higher temperature

Then mixing takes place in the housing with the thermostat controlling the mixing of hot and cold water to control engine temperature.

It's kinda like "magic" happens in the thermostat housing

KENO wrote: My Sherwood manual has a graph for various different impellers and their flow rates at various RPM. Maybe this will become this afternoon's experiment

Absolutely! We're overdue for one of your hands on true to the world testing's!

8122pbrainard wrote: KENO wrote: My Sherwood manual has a graph for various different impellers and their flow rates at various RPM. Maybe this will become this afternoon's experiment Absolutely! We're overdue for one of your hands on true to the world testing's!

Pete

You missed yesterday's episode.

It was the spark plug wire swapping experiment in LisaO's thread.

But anyways, I did the bucket test and 5 gallons in 15 seconds at 3000 rpm is a good number.

This was sucking from a bucket so all the engine cooling was still supplied.

ok. IR Gun in hand. Verifying temp tonight. I think my problem is the circulation pump. How hard is that thing to pull off? Before I pull it off, I was told to remove the drain plugs and verify flow increases as do the RPMs. No measure was given to test flow for this procedure. Once again, how hard to pull a circ pump? What should I be looking for?

I had a pump start making noise,the PO had maybe changed it when they put the new engine in. Dad then ran it almost 20 years in fresh water. When I got it apart almost all the fins on the impeller were gone,they had used an automotive pump and was in saltwater for several months. It never overheated though. If you can't find anything else and the temp gauge checks out it just might be worth pulling.

OK CCF Community - I come to you with GREAT SUCCESS Last night. Following Vince of SKIDIM's advise once again, I pulled the 9/16" drain plug on the block while running and hooked to garden hose. I did this to prove out the circ pump. Upping the RPM's did infact increase the spurting of water all over my carpet. So No need to pull the circ pump. I also got an IR gun from someone at work. Turns out he had it in his backpack that he carries everyday of all places!! I brought the boat down tot he lake, shot the engine and guess what!!!??? I caught my temp gauge in a lie!!! The gauge was reading well over 200 and I was shooting the engine top and sides and I was getting around 120 degrees. Then all of a sudden, the gauge settles in the a calm 160. Oh - All this with the original 143 degree t-stat installed. Took the boat out for a quick spin......160. Ran the engine for extended period of time at the dock, still 160. Ok, I see how it is....I caught you (my SN2001) in a lie and now you are going to tell the truth? But in all seriousness - WHERE AM I SUPPOSED TO SHOOT THE ENGINE TO VERIFY TEMP? I can't see how i can do it accurately because the sensor is hitting water inside the engine. I do also understand something explained above about the outlet side of circ pump on it was back up to t stat housing (larger diameter thing) - that shot at 125 as opposed to headers that were closer to 100. However I did shoot the bottom of the manifolds, the four exhaust ports leaving the engine and I got temps, 220-240......uh, oh. lets put it back on the trailer and shut her down until we understand the correct temp to shoot the engine and what temps should be where. All this help has been much appreciated.....

Keep in mind that when put back on the trailer gauge was reading 160 after about 60 minutes of engine run time. So something was/is lying. The sender or the gauge. Wonder which one is more likely to lie??. Wonder if I can install a stand alone gauge to verify the original in dash VDO?

I believe you can use a VOM to test the sender. Obviously you need to catch it in a lie first.

You should be able to test the gauge by removing the wire from the sender, and grounding that wire to the engine block. If it pegs the gauge consistently, the gauge should be good. Double check for loose/corroded connections at both the Edit: sender and the gauge.

Bri892001 wrote: Double check for loose/corroded connections at both the Edit: sender and the gauge.

+1 on this. I had a wire connection at sender come loose too.

phatsat67 wrote: Test or replace the sensor. Also, you need to verify that your gauges are receiving proper 12+ volts and have a good ground. Bad grounds and low voltage will make gauges read high regardless of sensor signal. If all of those factors test good your gauge is the culprit. Easy way to test the Gauge independent of the boat electrics is with power and ground jumper wires direct to the battery. This will give a 100% good ground and at least 12v power.

Yes and make sure there isn't any thread sealant or tape on the sender threads to the block. The block is the ground source for the gauge.