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09-06-2016, 08:16 AM | #1 |
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Engine Merc 888 (Ford 302) getting hot after warming up
My engine is intermittently overheating. Engine temp stays cool then all at once spikes up. Once the engine gets hot it doesn't want to cool down. Impeller in outdrive is new. Using 143 degree thermostat. I've been advised I could have vapor lock - I'm going to drill a1/8" hole in the thermostat flange to see if that helps. I not, I'm thinking it's the water pump on the front of the engine ma be the issue It's not leaking but I wonder if water is circulating. Thoughts?
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09-06-2016, 09:57 AM | #2 |
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Is it the original thermostat? (I read your other thread so I know you've done quite a bit of work on the boat / engine.) If original, it sure sounds like a sticking thermostat. I had a similar issue on our 5.7 Mercruiser earlier this summer, replacing the thermostat took care of the overheat. Pretty straight forward job that could be done in the water on my boat.
If the thermostat and raw water pump impeller (the one in the outdrive) have been replaced, it's possible that you have some corrosion blocking flow in the exhaust risers and manifolds. This typically means replacement of those parts.
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09-06-2016, 10:33 AM | #3 |
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Engine overheating
It's a new thermostat. As for the manifold and risers, they were replaced about 14 years ago. The boat has only been run in fresh water. The boat has not had many hours on it since those items were replaced, less than 100 hours. There were a number of years we didn't use the boat at all due to illness in the family and other priorities taking precedence. It's possible that some scaling and some surface corrosion has occurred but probably not enough to obstruct the channels. Thoughts?
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09-06-2016, 11:47 AM | #4 |
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Engine getting hot
For this one I plan to drill a 1/8" hole in the thermostat flange. That can address the vapor lock issue if that's the issue. I can also replace the water circulating pump, but I'm not sure if that's the issue and especially when it's not leaking. Maybe they go bad in time and don't leak??
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09-06-2016, 01:09 PM | #5 |
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vapor lock?
Vapor lock is a carburetor issue not a cooling system issue.
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09-06-2016, 01:40 PM | #6 |
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I would say the thermostat is faulty even though new, cheap enough to replace and see what happens first. also check to see that the impellar in outdrive does not have and blockage from sucking things up, with the level of the lake could be a possibility
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09-06-2016, 03:09 PM | #7 |
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Engine heating up
Any chance the water circulating pump (front of engine) is faulty?
I will pull the thermostat to see if that removes the symptom. If so then the thermostat is faulty. I'll still probably drill a 1/8" hole in the flange. I've been told by enough career service managers that the lack of this could keep the water from circulating properly, even if the thermostat is working. I'll let you know what I find out.... |
09-06-2016, 04:10 PM | #8 |
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Perhaps the pumps are worn out?
I've seen some pumps replaced by a mechanic lately, the pump body itself was all worn out because of sand and things that have been sucked up and run through the engine over time (such as spending a lot of time going to shallow water sand bars, or sucking up lake mud when the water is low). So when you replace the raw water impeller, be sure to check the surfaces of the pump housing to see if there is excessive wear. Also, if the pump bearings are wearing out, it could allow air to be sucked into the system and could cause a loss of cooling as water wasn't being efficiently sucked into the system.
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09-06-2016, 07:24 PM | #9 |
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Have you tried running it without the thermostat installed?
That might tell you if the trouble is elsewhere. |
09-06-2016, 08:04 PM | #10 |
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Engine issues
I'm going to pull the thermostat and check it to make sure it opens and stays open at the correct temp. Also run the engine without it. If the engine stays cool without it I can narrow things down. If it doesn't the water circulating pump is what I suspect. Impeller in the out drive is new. The one I replaced looked new. No wear in the impeller housing. no gunk, sand or mud in the impeller area. I have other things to check. I'll let you know what find.
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09-07-2016, 08:04 AM | #11 |
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Engine getting warm
I have not checked the water line between the gimbal housing and transom. Is that easy to check to see if it's crimped or damaged?
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09-07-2016, 08:28 AM | #12 |
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Is this an issue that has begun immediately after repair work?
If you had the outdrive off, it may help to remove it again and look for anything not quite right with the previous reassembly. What brand/model/vintage outdrive is this? |
09-07-2016, 08:31 AM | #13 |
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Is the issue only at idle, or when you try to power up?
Have you tried starting the engine out of the water, with muffs? This should give you an idea of if water is passing through the engine. The added pressure from the hose may overcome the water pump so you can't rule that out....but if you're not seeing water drop from the gimbal housing then your engine isn't getting water and had a block somewhere. If it runs great and doesn't overheat, then I would suspect the water pump. To check the water hose from the gimbal housing you need to pull the outdrive off. What drive do you have? |
09-07-2016, 08:35 AM | #14 |
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Correct!!!!!
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09-07-2016, 08:59 AM | #15 |
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09-07-2016, 09:05 AM | #16 | |
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Quote:
I'm going to run the engine without the thermostat and see what happens. |
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09-07-2016, 09:18 AM | #17 | |
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The gimbal housing bellows (I'm assuming you mean for the universal joint) should not have any water in it - and will not have anything to do with cooling the engine. I would get a large trash bucket of water and start the engine with the drive submerged..make sure to leave the hose in the bucket. If you don't see water coming from the exhaust, inspect/replace the impeller. |
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09-07-2016, 10:00 AM | #18 |
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It's been a while since I've messed with my drive personally but I do recall that hose as being prone to crimping. If you tilt the drive up to trailer position, I think you can see it from below but it's been a while. Also, mine is a first generation Alpha, yours pre-dates it. I like the ideas mentioned of running the boat out of the water on muffs and seeing if you're getting water out of the exhaust. You can also check the temperature of the hoses that inject water into the exhaust elbows vs. the engine side hoses to get some idea if the raw water is flowing.
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09-07-2016, 12:05 PM | #19 | |
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09-07-2016, 12:07 PM | #20 | |
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09-07-2016, 12:40 PM | #21 |
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So when exactly does the engine spike in temperature? What are you doing prior?
To read the exhaust manifold/riser/elbow temperatures I would use a simple IR heat thermometer. https://www.amazon.com/Raytek-MT4-No.../dp/B0002198GY (as an example) |
09-07-2016, 01:28 PM | #22 | |
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As for the engine temp, I can be on the lake or on a hose and it shows hot after 5 to 10 minutes. It usually starts jumping up. It's not a slow climb. Its shows 1/4 into the green, then all at once jumps up into high green or into the red. On the hose is appears lots of water is being sucked through - a lot is coming out the exhaust and prop hub when the engine shows hot. The manifolds and risers are hot to touch, but that might be normal? |
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09-07-2016, 01:37 PM | #23 |
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Where is the engine temp sensor on the Merc 888 (Ford 302)? Could that be faulty?
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09-07-2016, 02:05 PM | #24 | |
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It's possible the sensor is bad, but if the manifolds/risers/elbows are to hot to touch then I doubt the sensor is the problem. |
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09-07-2016, 02:30 PM | #25 |
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The risers are pretty hot. Same for the manifolds. I wouldn't be able to put my hands on them and leave them there.
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09-07-2016, 02:32 PM | #26 | |
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09-07-2016, 02:46 PM | #27 |
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Closed cooled, or raw water cooled (i.e. do you have a heat exchanger and antifreeze)?
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09-07-2016, 02:52 PM | #28 | |
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This was posted elsewhere and should give you some great idea on how to diagnose the issue.
http://forums.iboats.com/forum/engin...rheating/page2 Quote:
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09-07-2016, 04:47 PM | #29 |
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09-07-2016, 05:11 PM | #30 | |
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09-07-2016, 05:24 PM | #31 | |
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100% RAW Water Cooled Split System I would follow that path from inlet and make sure you are getting good flow. |
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09-07-2016, 08:05 PM | #32 |
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The diagram was really helpful. Question - the two exhaust outlets on the lower back of the boat - if those are spitting a lot of water at idle, then more at 1,000 RPM and increasingly so as RPMs increase, wouldn't that indicate good water flow is traveling through the engine or the manifolds and risers, or all the above? How do I know if the engine is getting good water flow from the circulating pump?
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09-07-2016, 08:48 PM | #33 |
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It's hard to tell. Based on some other threads it sounds as if the manifolds on that engine can get pretty warm.
At this point I'm guessing the water pump for the engine side is not supplying enough water flow (or has air bubbles) to cool the block. I'll see if I can locate where the temp sensor is located. Sent from my iPhone using Tapatalk |
09-07-2016, 09:12 PM | #34 | |
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09-07-2016, 09:59 PM | #35 | |
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09-08-2016, 12:04 PM | #36 |
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Great point. I installed one upside down 30 years ago in my van. There should be a flow arrow on it somewhere. Generally speaking, the spring portion should be submersed in the engine block and when the thermo opens it goes to lines that will circulate to cool.
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09-08-2016, 12:14 PM | #37 |
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I just swapped my tstat (1988 5.7 Chevy / Mercruiser) The temperature sensor for the gauge was located in the thermostat housing just below the thermostat.
From just reading your last post, I think you have the thermostat in correctly. Just as shown in the diagram that HellRazoR004 posted above.
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09-08-2016, 12:21 PM | #38 |
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Here is a 302. Not sure if your housing looks like or is connected like this but I think you get the idea of how it works. The nice part is you might find this is your problem.
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09-12-2016, 05:55 PM | #39 |
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Okay - it appears the engine block stays cool until the thermostat opens up. Once the thermostat opens up the block gets hot. Water volume coming from the outdrive appears to be strong. Can't tell if it's bubbling from the hose feeding the water pump. Now what?
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09-17-2016, 08:09 AM | #40 |
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What about the water pocket cover? If that's warped or scorched it could create a water flow issue. Is that easy to replace? It's easy to get to but would the bolts be tough to loosen?
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09-17-2016, 09:13 AM | #41 | |
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09-18-2016, 04:28 PM | #42 | |
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09-19-2016, 07:43 AM | #43 | |
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That said, squirt some oil in the cylinder with 75 psi and see if the compression test results improve If they do, it's likely not the head gasket. 105 to 120 on the other 7 cylinders is too low, IMO and the engine is tired. Now would be a great time to pull it and freshen it up a bit. With luck, you can just do a valve job, hone the cylinders, and put new rings and bearings in it. If the engine has a history of extended salt water use, it may make more sense to just replace the long block as the salt can make the coolant passages rather thin. Ford 302s are not exactly rare or expensive. A 351 Windsor would likely bolt right in too, but might require different ancillary bolt on parts since it has a taller deck height and different firing order than a 302 if memory serves. |
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