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8.1L crusader coolant

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Okiedokie

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Hi all, this is my first post. I have read a lot of the old posts in this forum over the last year after I purchased my boat with twin 8.1L crusaders. The boat is a 2004 Tiara 3100 and the engines are original equipment with just over 400 hrs now. Last year I had the stbd engine running at 190 on the gauge while the port was at 180. I confirmed the stbd was hotter with an infrared temp gun. The boat came from salt and I moved it to fresh.

Over winter I replaced manifolds, risers, and raw water pumps along with raw water intake hoses. I had the HX removed and flushed and cleaned and coolant replaced. This spring both engines were running same temp at 180. I recently noticed the port engine is heating up much more quickly then the stbd, and will actually get to 185 or so at idle. First time I noticed this I thought I picked something up on the intake, but water flow looked good at idle and the risers were cool to the touch. When I took it out and got up on plane the temp dropped back down and both engines ran at 180 like normal. So I thought no big deal whatever it was is now gone. But when I started them up again to get back home it did the same thing - heats up quick to 185 while the stbd is at 150-160 then dropped back down after I got on plane.

I am going to the boat tomorrow, what should I look for? I am going to clean the strainers. I noticed the overflow tank on the port engine is well over the "full" mark and I certainly did not overfill it after the coolant was replaced in the spring.

Any other relevant details I am leaving out?

Edit: obvious detail I left out is that thermostats were also replaced along with HX caps while all the other work was done.
 
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Welcome to ME.com!

raw water flow is real hard to gauge accurately by eye so be careful with that. Make sure the suction side of the raw water inlet is tight - no air leaks...the other item you didn't mention is the oil coolers....sometimes, due to their small passages, they will collect any junk the slips thru the strainers...
 
Thanks for the welcome and for the reply.

I did have the oil coolers pulled and inspected. The mechanic said they were fine. I have put dozens of hours on the engines since all of the work was performed on the cooling system over the winter and had perfect temps all along. This just developed last weekend, so I haven't pulled the coolers since then.

What might cause the coolant level in the overflow tank to be high? Air entering in the closed side somehow?
 
high coolant....?? depends upon how you are checking it....assuming 'when cold' for both observations, and the more recent observation giving the higher level, that's likely not good....initial thought is as you suspect but I'd lean towards combustion chamber leak into the closed coolant side vs 'air' - there's no way 'air' would displace the liquid without some help (pressure)....

If you are comparing two observations but a different points in an operating cycle, I could go either ok or not...
 
A possibility is a small air leak in the coolant overflow hose on the port side caused by a poor connection at the cap end or a hose split. When the hot engine cools it is supposed to suck coolant back in to replace the shrinking volume of coolant as it cools, but it sucks in air instead. Your cold coolant level in the overflow tank then is too high. Upon startup the circulating air bubble makes the engine run hot. As the air leaves the system eventually all is well (including comparing the fluid levels) until the next cool down cycle when it all repeats.

Actually I am not very high on that explanation, but it falls under the easy things to check first.

If all this started after the work was done then some change there could be the cause. Also, there can be subtle differences between engines if one has a hot water heater (serving as an wngine warm up bypass route) and the other does not. Mine are not the same.
 
The stbd engine that is acting normal now is the one with the water heater in the loop. Previously it was running 10 degrees hotter than port (before all of the work)
 
OK, water heater is on the "good" engine. Understand we are talking long shots here, as there are so many things that can cause weird cooling behavior. But on some Crusader engines (specifically my year 5.7 MPIs, and perhaps others such as yours as well) you are supposed to have bleed holes in the thermostats. These make it easier to bleed air out of the system, but the also, on these engines, serve as a way for low amounts of water to get through the closed thermostat during warmup, thus preventing boiling on the rapidly heating cylinders, and allowing hot water to get to the thermostat so it will open in a timely manner. Some Crusader engines use other tricks and designs to accomplish this. But here is the point; if you have a hot water heater on the engine it will also give you that circulation and you don't really need the holes in the thermostat in order to get the smooth warmup. So maybe, when your thermostats were changed, they used ones with no holes, and maybe, your port engine requires a stat with the holes while you starboard side can actually get along without them. Two "maybes" there, but like the advice on a possible air leak in the overflow hose, it is something easy to look at and eliminate.
 
Had a minute and just took a look at your layout for the 8.1. Looks like Crusader has put in a bypass hose off the thermostat housing to handle the issue I discussed above. I doubt now that holes in the thermostat are applicable with your layout.
 
Okiedokie said:
I recently noticed the port engine is heating up much more quickly then the stbd, and will actually get to 185 or so at idle. First time I noticed this I thought I picked something up on the intake, but water flow looked good at idle and the risers were cool to the touch. When I took it out and got up on plane the temp dropped back down and both engines ran at 180 like normal. So I thought no big deal whatever it was is now gone. But when I started them up again to get back home it did the same thing - heats up quick to 185 while the stbd is at 150-160 then dropped back down after I got on plane.
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I'm not sure I see this as a problem. What "heats up quick" at idle is the exhaust manifold. Normally, the EM will heat up >180 before the thermo opens. AS LONG AS combustion gases are not causing this. Might do a test strip on the coolant to find out for sure.
 
diver_dave said:
I'm not sure I see this as a problem. What "heats up quick" at idle is the exhaust manifold. Normally, the EM will heat up >180 before the thermo opens. AS LONG AS combustion gases are not causing this. Might do a test strip on the coolant to find out for sure.
Click to expand...

I probably wouldn't have thought anything of it, except: 1) it is doing something different than normal which raises suspicion that something has changed / is wrong, and 2) the stbd motor is at 140-160 degrees while port is >180 before I made it out of the inlet.

I will try to find a coolant test strip. I still haven't made it back to the boat since I posted. I am hopefully heading up today and will clean strainers and test coolant if I can find a test strip.

Thanks again for the replies. I will report back how it goes.
 
Went to the boat yesterday. I cleaned out the strainers and removed the excess coolant in the overfill bottle back down to the "full" line. Fired up the boat and got things ready to head out. By the time I made it out of the harbor the port motor was 185-190 and stbd was 160. Hit 3k rpms to get up on plane and they both settled at 180. I need to figure out what to check next. Possibly the new thermostat on port side is bad and sticking?

Edit: btw, the strainers were clean, so no evidence of picking up a bunch of stuff in raw water side.
 
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