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| Overheat at idle https://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=14961 |
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| Author: | TFD2001 [ Mon Jun 27, 2016 6:24 am ] |
| Post subject: | Overheat at idle |
So, got a issue that seems to be getting worse. Have an engine that will tend to creep up temp wise while idling (such as in the marina), after I've been running. This has happened a couple of times over the last few years, but this year, it's happening about every third run (not exact). If I get the RPM's back up, she cools right back down. I haven't checked the impeller yet this year, but I'm highly doubtful that this is the issue (will be checking that this weekend), and I replaced both thermostats 2 years ago, when it first occurred. My next thinking is either the engine water pump, or, a Riser issue? Thoughts? |
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| Author: | 230 Mike [ Mon Jun 27, 2016 12:49 pm ] |
| Post subject: | Re: Overheat at idle |
IMO, most likely would be impeller, 'stat, and water pump in that order. |
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| Author: | fi.na.tine [ Mon Jun 27, 2016 1:03 pm ] |
| Post subject: | Re: Overheat at idle |
My vote is on the impeller. Even if it's just a year old does not mean you didn't suck something up that jammed it up or took out a fin or two. |
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| Author: | rpengr [ Mon Jun 27, 2016 1:12 pm ] |
| Post subject: | Re: Overheat at idle |
I agree with the impeller and/or raw water pump housing. Most other issues will result in high temperatures when running harder. Only the impeller is weakest at low rpm. Impeller, or too much clearance in the raw water pump housing due to wear. Another possibility is an air leak anywhere on the suction side of the raw water pump (including hoses and oil cooler). However, this is not likely because you would notice water drips when the engine is off. |
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| Author: | LouC [ Mon Jun 27, 2016 3:25 pm ] |
| Post subject: | Re: Overheat at idle |
One thing that's missed often is that if you suck up a bit of sand, the sand will make grooves in the wear plate and even if the impeller itself looks new, if the wear plate gets worn then you can have this problem. If you're in a fresh water region, I'd doubt clogged risers but you never know. Some fresh water can be corrosive. But then, you'd be getting high riser temps right after coming off plane. I like to check both the idle temps (about 100*) and max riser temps after coming off plane (about 135*) if I see temps higher than that then I start looking for problems. If you don't have one get an IR temp gun. Take some readings from the risers like I said and also from the intake manifold right under the thermo housing. I have found that this area is the one that most closely matches the dash gauge. If my temp gauge says 160 that area will read about 150-155-157 usually. |
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| Author: | TFD2001 [ Mon Jun 27, 2016 9:10 pm ] |
| Post subject: | Re: Overheat at idle |
Thanks for everyone's input! So, the boat was originally a salt water boat that was taken care of immaculately, and rack stored when not in use, and flushed prior to going back to the rack. But still, it was in salt with the first owner. I'm in the 4th season of ownership now, and it's a fresh water boat since my ownership. Highly doubt that we've been in any sand, but can't rule out what may have happened with previous owner. When I come off plane, she doesn't instantly warm up, it takes a bit, and isn't an every occurrence, but over the last few weeks, has seemed to become more consistent. I do have extra impellers and will be checking and changing if necessary this coming week. If it truly is that easy, then good deal, but it would only be that impellers second season, and I usually am able to get 3 at least, and when removed, show minimal wear then. Talking to a mechanic (cars mostly) friend today, he thought that if the risers would be plugged, that I might notice some loss of power too, which I'm not seeing. The other, what I consider minimal possibility, would be a gauge issue I guess. So, I may swap the wires on the gauges around too, to see if I get the same results on the other gauge. Thanks! |
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| Author: | LouC [ Mon Jun 27, 2016 10:15 pm ] |
| Post subject: | Re: Overheat at idle |
Well that adds some information, so if it was a salt water boat until 4 years ago, then it was used in salt from 2004-2012, right? So that's 8 years of salt water use. Now its hard to guess really but here in salt water land, we would have been checking the risers and manifolds at about 5 years, and probably replacing at 8. With the flushing they might have held up better, its hard to say. Do you see any leaks around the riser/manifold joint? That's a sign for sure that they need to be changed. Do some checking of the intake manifold right under the thermo housing with the IR temp gun, see how that matches up with the dash gauge when its running hot. Clogged risers wouldn't cause a loss of power because the clogging takes place only in the cooling passages, not the exhaust gas passages. But for sure they will get hot if they are clogging esp after running on plane. Also take a reading of the risers at idle speed and then run the boat on plane and after you come off plane check them again. On mine I get about 95-100*F at idle, and 135*F after coming off plane, but they cool off pretty fast. Running temps, are usually about 160*F, except after coming off plane, it will rise to 175*F but soon cool back to 160*F... |
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| Author: | TFD2001 [ Tue Jun 28, 2016 6:24 am ] |
| Post subject: | Re: Overheat at idle |
Thanks for the info! Last I checked, I had no water anywhere on the exterior of the engine, and the bilge was bone dry, but I haven't been in the engine compartment in a month probably so, as I said, I'll be checking it out, this week, and see what we have now.. |
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| Author: | rpengr [ Tue Jun 28, 2016 7:37 am ] |
| Post subject: | Re: Overheat at idle |
TFD2001 wrote: ...Talking to a mechanic (cars mostly) friend today, he thought that if the risers would be plugged, that I might notice some loss of power too, which I'm not seeing. The other, what I consider minimal possibility, would be a gauge issue I guess. So, I may swap the wires on the gauges around too, to see if I get the same results on the other gauge. No, plugged (rusted) risers would not cause any loss of power. It's only the water passage ways that would be plugged up, not the exhaust passageway. Considering the 12 year salt/fresh history, it's almost guaranteed that you should change your manifolds and risers. Do-it-yourself for under $800, vs rebuilding your locked-up engine if they rust through and spill water into your engine when not running. (I've been there with my previous boat). Remember that all of the water getting pumped INTO the engine (by the raw water pump) must go OUT of the engine through the exhaust manifolds/risers. Your problem could very well be a combination of rusted manifold/risers and wear in your raw water pump housing (leakage around impeller...most noticeable at low RPMs). Or it could be either issue by itself. |
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| Author: | LouC [ Tue Jun 28, 2016 7:42 am ] |
| Post subject: | Re: Overheat at idle |
And you might not actually see water on the manifold to riser joint, but rust stains coming from that joint. Do some checking of temps and then let us know what you find... |
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| Author: | captkevin [ Thu Jun 30, 2016 9:30 am ] |
| Post subject: | Re: Overheat at idle |
Do you have Volvo or Mercury? |
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| Author: | TFD2001 [ Thu Jun 30, 2016 10:19 am ] |
| Post subject: | Re: Overheat at idle |
Volvo |
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| Author: | captkevin [ Thu Jun 30, 2016 11:59 am ] |
| Post subject: | Re: Overheat at idle |
Reason i ask is Volvo uses brass pumps. On our last boat we were having a similar issue. Tried replacing the impeller & no change. Ended up the inside of the pump was worn out. Had be baffled. Out of desperation I removed the pump & brought it to the dealer. Parts guy took one look at the pump & said it is a river boat & the inside of the pump is wore out. Previous owner used boat exclusively on the Mississippi river & due to the amount of sand in the water over time it had worn the inside of the pump. Dealer said they see it quite often. Bought new Volvo pump for $350 bucks & problem solved. I must have had it apart 6 times & tried 2 impellers & had no clue. |
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| Author: | LouC [ Thu Jun 30, 2016 3:59 pm ] |
| Post subject: | Re: Overheat at idle |
A couple of years ago I got stuck on a shoal at a very low tide and had to power off. I saw elevated running temps, not overheating but hotter than normal. Took the impeller housing off and found that the impeller itself still looked new but the wear plate was noticeably scored. Replaced the plate with one of my many spares (I've got a box full of Cobra spares) and back to normal 160-175 max. The nice thing about the Cobra impeller design is that's it very easy to take apart, (in the rear of the upper gear housing under a plastic cover) and the whole works, is about $40! A lil OMC gasket sealer and you're back in business. So the impeller depends on the housing/wear plate to make a tight seal for it to pump enough water..... |
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