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thermostat question on older crusader

infinityron

Contributing Member
I'm replacing the tstat on my older vintage RAW WATER cooled 454. Not overheating but more preventative than anything. The temp gauge not going high but fluctuating a bit which is unusual. My engines pretty much run at 145 all day long. I ordered and await a factory replacement tstat housing kit complete with the housings and internals. My question is.....new one is coming with a spring and a "relief valve"? in addition to the 142 tstat. When I took the old one apart, there was no spring or other valve. What is the purpose of this other valve and spring I am supposedly receiving? Do I need it? Engine was not overheating without it, so I'm just curious. Can't find anything online about older crusader marine cooling guts. Boat is a 1976. I think the blocks are about 1990's but for all I know they could be original. And yes.....they are raw water cooled in salt water and running great.
 
The spring loaded poppet valves help to maintain a stable pressing in the coolant passages within the block...but I can't tell you when Crusader started using them...If you have serial numbers, we can give you a good idea when the blocks left the factory (year-wise anyhow).

Who got you the part number for the housing kit? did they ask for a serial number?
 
The spring loaded poppet valves help to maintain a stable pressing in the coolant passages within the block...but I can't tell you when Crusader started using them...If you have serial numbers, we can give you a good idea when the blocks left the factory (year-wise anyhow).

Who got you the part number for the housing kit? did they ask for a serial number?
I ordered the part based on photo of housing stamp and resemblance. The block casting on that engine is 10069286
 
update.....cleaning the old housing, I did find the poppet valve in it. So, the part I received is correct and I am reassembling.
 
the block appears to be newer...I'm guessing something happened with the original engine and that one went in with the original bolt on parts...having the serial number would be good because that should address the bulk of what you have, for the bolt ons, anyhow.
 
Guys...refreshing this thread a bit, I have a couple dumb questions....First, after replacing my t stat housing with new tstat and poppet valve identical to old one, and with a new sender as well, the temp gauge behaves differently than before. With old stat and sender, the gauge ALWAYS settled at 145 degrees operating temp and never moved. This is a raw water cooled engine. Now, with new tstat and sender the gauge settles in at about 170 degrees and never moves. I installed a 142 degree tstat. I also shot the block and manifolds all over the place with ir gun and getting fluctuating readings. for example if I read the tstat right next to the sender, it reads a lot colder than the 145 degrees appearing on the gauge. I would think that those two numbers would be pretty close? The risers and elbows are all cool and comfortable to the touch.
I'm theorizing that either the old sender was inaccurate or the new tstat is a higher temp rating than old one? Also, I am reading the engine all over the place, i.e. around the tstat, the risers, elbows, intake manifold in multiple locations....and for the most part I get readings less than the 145 degrees showing on the temp gauge, except....one section on top of the intake manifold right behind the carb, I saw as high as 190 but varying between 175-190.

I know I want to keep the raw water cooled engine below 160 to avoid salt crystallization, but what should the expected operating temp be on 454 crusaders raw water cooled? And where is the key spot to aim ir gun for best indicator of actual engine temp?
 
While IR guns are great, they are not all known for being accurate, especially if they have a large spot size and you are measuring from more than of foot of separation.

For measuring around the tstat housing, usually, the best results come from the interface with the housing and the intake...if you get too close to the raw water side, it will cool off pretty quickly.

On the intake manifold, there is a passage going between the heads, under the carb, where exhaust gases flow to aid in vaporizing the fuel...and to work the old style choke coils...if you get anywhere close to that passage, you will see the higher temps (like the 190 deg F point you saw).

the 160 deg 'upper limit', to minimize the salt precipitation, applies to the exhaust system, not the engine...

Did you take all of your data at the pier or were you out cruising, with the engine under load?
 
While IR guns are great, they are not all known for being accurate, especially if they have a large spot size and you are measuring from more than of foot of separation.

For measuring around the tstat housing, usually, the best results come from the interface with the housing and the intake...if you get too close to the raw water side, it will cool off pretty quickly.

On the intake manifold, there is a passage going between the heads, under the carb, where exhaust gases flow to aid in vaporizing the fuel...and to work the old style choke coils...if you get anywhere close to that passage, you will see the higher temps (like the 190 deg F point you saw).

the 160 deg 'upper limit', to minimize the salt precipitation, applies to the exhaust system, not the engine...

Did you take all of your data at the pier or were you out cruising, with the engine under load?

Mark, you are one of the most helpful and gracious guys I have encountered on internet forums. I always learn from you and there never any sarcasm.
I took the readings at sea but not pushing it. Rpms were 1500 on my boat doing about 8 knts sog. My boat is actually a 32' planing hull designed to get up and go, but in honesty, due to age of the machinery and fuel cost, I have never pushed the boat to get up and plane. It would probably take 2500-2700 to hold it up cruising about 20 knts. In 4 years of ownership, and routine frequent use, she has never failed me. Engines purr along, boat on auto pilot, watching the scenery. My goal is to keep it from falling apart by keeping it slow and easy.
 
thanks for the kind words.

If you are going to be 'not pushing it' its likely you'll never see anything beyond the 170 recent peak and you can use that as a reference...another option would be to make sure the overtemp switch in the coolant loop works and then gauge's inaccuracy becomes a moot point...
 
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