[ReelMagic]

I owned a 1997 31 Open w/454 FI Crusaders and had a similar problem several times. It turned out to be the way the Thermostat was seated in the "Tee" housing.  It wasn't seated fully allowing the closed loop (antifreeze) water to partially bi-pass the engine itself. One line on that "Tee" is a bi-pass line which allows the engine to warm up prior to reaching operating temp then opening fully to allow full flow through the engine. When incorrectly seated in the housing antifreeze flow though the engine is reduced significantly because its bi-passing causing the engine temp to increase... Take a look to ensure the thermostat is seated completely... It wasn't much but it caused my engine temp to increase approx. 20-30 deg. Once re-seated engine temp went back to normal (160 deg).. M2C...

[0007Boating]

Awesome. I will check that out but i just replaced the thermostat and the temp didn't change. But I'm also stuck on just one exhaust manifold getting hot.
Besides, I'm the guy that gets all the problems that no one has seen before. Im just lucky i guess. Lol

[ReelMagic]

Take a careful look at the thermostat and the housing to ensure the thermostat is seated correctly. I made that mistake when I thought the thermostat was causing the temp when in fact it was due to the thermostat not being seated completely.

[Sans Peur]

I have owned a few gas inboard Mercs and all of them had heat exchangers and coolant running in the engine. None of them had coolant running through the exhaust manifold and elbow. The exhaust manifold and elbow always had raw water running through them.

Raw water came in from the impeller pump,through an oil cooler, to the heat exchanger and then to the exhaust manifolds and finally up into the elbows (shower heads) and out the side of the boat with the exhaust. Manifolds get clogged internally and will overheat. They are a "wearable " item and have to be replaced periodically.

[0007Boating]

Thanks guys. It is definitely fresh water cooled as there is a block off plate between the manifold and the elbows to block the antifreeze from entering the elbow. i took the hoses off the manifold and the antifreeze came out.

[ReelMagic]

There is/was a big difference between Merc's and Crusaders and how they fresh water cooled their engines. Merc's typically used seawater (salt) to cool the manifolds/Elbows while Crusader used larger heat ex-changers allowing them to cool the manifolds as part of the fresh water loop as well. It's a better solution than the Merc's in that you didn't have to worry or change them as part of maintenance of the salt water loop. M2C

[Sans Peur]

Cool Beans. That is good to know. I always had Merc's and never had a crusader.

[Misdirection]

You may want to post your questions over in the Crusader forum at MarineEngine. At first glance there seems to be quite a few articles about replacing manifolds on salt water boats.

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[dbriceno]

It's a very good idea to change your manifolds every 10-15 years if you want your motors to last a long time. Every 5 years for your risers. The odds are if your manifolds have a Crusader emblem on them, they are original. Why spend $50 a piece for new emblems.

[0007Boating]

Went down to the boat yesterday and here's what i did. I replaced the coolant hoses going to and from the exhaust manifold, no change. Then i swapped the oil coolers from one engine to the other, no change. I swapped the temp sensors, no change. I looked at the impella and that was fine. Last resort i swapped the temp gauges, no difference. I ruled out as much as i could without spending too much money but still nothing. I decided to take her out for a test run under a load instead of sitting at the dock. When i was running at 1000 rpm's the same engine was getting up to almost 200 deg. once i got out of the no wake zone i brought her up to cruising speed 3200 rpm's and the temp came down slightly to around 195 deg. I then opened her up for about 2-1/2 min toped out at 4600 rpm's and the temp came down to 180 deg. Came back through the no wake zone at 1000 rpm's and too my surprise the temp only came up to 185 deg. is it posable running her hard for a few min cleared something out of the cooling system? Im going out today with the family, keeping a stiff eye on the temps and i will post the results when i get back.