Engine running 'Warm' - Maxum Boat Owners Club

shrew · 07-12-2010, 04:25 PM

I repowered my 2800 SCR with a 496 (Fresh Water/Closed Cooled) in the spring of 2009. The new engine ran great all season, then I had an overheating issue in Sept. 2009. When I hauled the boat I found the outdrive pickups had a lot of barnacle growth. I completely cleaned out the pickups and sanded and primed and painted the outdrive. I launched the boat this season in mid-may and there didn't seem to be any overheating issues. (Problem solved, or so I thought).

Recently, I'm seeing the engine temps running warm. The guage shows 175 F at 12 o'clock. It's always been my understanding that the guages are typically set so the majority run at or around 12 oclock so when you glance at the guages they all easily show when at normal operating values. when I used to idle at headway speed the temp guage would be just below 175 (170?). When operating on plane it would be at or just slightly past 175 (178?).

Lately, I'm seeing the temp guage running at what looks like 185-188. It seems to idle around 178+, and when running between 3200-3800 rpm's it is halfway between 175-200. (again 185-188?). This certainly seems warmer than it should be, but not quite overheating. When I come off plane and idle into anywhere, the temps shoot up to 190-195, then drop back down to 178-180 after a few minutes.

I would expect the temps to shoot up temporarily after when running at idle/headway speeds after running on plane at higher RPM's for some time as the raw water coolant volume is lowered. The temps do drop. So, here is my question(s):

1) Should a closed coolant system show an increase in temps after you slow down? After all the raw water is only cooling the manifolds, risers and heat exchanger.

2) I did check the pickups and they look clean. I can't see inside the drive so I wonder if the debrie from cleaning the pickups may have been sucked up and are now causing minor blockages in passages of the manifolds, risers and heat exchanger.

Where do I go from here? Any thoughts would be greatly appreciated.

Steve

seapuppy · 07-12-2010, 04:36 PM

I would check 4 things....1)is there a bubble in the coolant system.??..burp the system if you can...2)is this a new thermostat...??check replace.....they are relatively cheap...check the heat exchanger...take the end plates off and run a metal coat hanger or a dowel into each tube to clear it for trash..
...and finally...the impeller of the raw water pump may have ingested some trash and have messed up the blades...so change that out.....

SP

shrew · 07-12-2010, 06:16 PM

Many thanks SP, that stears me in the right direction. Here are 2 thoughts I had after reading your post.

1) I had an issue with my Honda CRV about a year ago. The temps would rise, rise rise, then fall back to normal. Over and over. Only by running the heat at full blast would the temps stay normal. It turned out I had an air bubble in the cooling system and, once burped resolved the problem. IT never occurred to me to correlate this to the boat. One of the frustarations I've had is SOMETIMES, the engine runs fine at idle (170). Sometimes warm. Sometimes the engine runs at between 3200 -3800 RPM's at about 178, which looks good. Other times, it starts running about 188. I was on vacation all last week and kept banging my head saying "It was warm on the ride over here, now it's running normal.....WTF!!!????" This went on all week. Never was the temp so high that is was an issue, just a concern for things possibly to come.

2) When the barnacles were clogging the intakes, there is no way to 'pull' them out. You can only poke them in to open the holes. I suspect that a bunch of material was pushed into the drive in the process of clearing them out. As we know barnacles can be hard and shell-like. I was thinking that the barnacle debri may have accumulated in teh passages, now I have to wonder if they tore up the impellor in the process.

I'll change the impellor, thermostat (it's new with the engine), burping the coolant and flushing the exchange and see where that gets me.

Many thanks, as always. I'll let you know how that goes.

tackleshep · 07-15-2010, 08:26 PM

Shrew,

Let me know how your project goes. My new purchase immediately had an engine problem. The port engine was overheating shortly after coming to plane. The interesting part is that both engines operate exactly the same at idle and then at low RPM's. When you bring her to full throttle they both increase at the same rate until the starboard engine tops out at the 175 range while the port just keeps getting hotter. When you back off my port side shoots up a little more and the starboard collapses and fast to 150 or so. The port takes a few minutes to cool back to normal.

We have replaced the impellers and thermostats plus cleaned the drive of all the crap around here (we have those bastard zebra mussels) and it still getting hot. Luckily for me it's still on the marina and former owners dime as it was part of the deal but it's getting a little frustrating. I was talking to the shop guy today and he is checking flow today or tommorrow then going to run it without a thermostat. (we don't have any cold boating weather around here and he wants to know it's not a problem with that. After that were down to the oil systems or as you indicated something in the in or outtakes blocking a the amount of water necessary. Let me know if you get yours under control and how, I'll do the same.

Thanks

Marc

seapuppy · 07-15-2010, 09:24 PM

check the heat exchanger....that may have those mussles growing in there..

SP

shrew · 07-15-2010, 09:49 PM

I was talking to my mechanic about this (while discussing another, completely unrelated topic) and he seems to think that I'm operating in normal ranges and suspects the warmer water is the factor. My reply was, "If that's the case then boaters in Fla. are running regularly in the 190's, that doesn't make sense". He indicated that Mercruiser has tradionally put smallish heat exchangers on the engine. The rise in temps. when I slow to to headway after running for some time is due to the decrease in water flow at slower speeds while engine temps are high because I just came off plane.

I was banging my head because on some runs it looked pretty good, on others not so much. he contended that as I come up the river and get into coves, bays and shallower water the water is warmer, where as when I get out into open water it's colder. He also insisted that earlier in the year the water temps were colder and are warming very fast. He said he's had 4-5 similar calls this week. I'm not sure I'm buying what he's selling.

New engine was installed last July and launched last July. Boat was pulled in late Sept. and relaunched in late may. I can't believe I have that much growth, however I do suspect the barnacle growth I cleaned up may have been sucked into the works and may be partially clogging passages.

seapuppy · 07-15-2010, 10:13 PM

as I said...take the end plates off...run a coat hanger or dowl thru the rods and push out any crap that is blocking the heat exchanger ....if there is just the slightest amount of crap..it will cause a less efficient heat exchanger operation and temps can vary wildly..

SP

tackleshep · 07-20-2010, 03:28 AM

Yeah I even removed the thermostat completely on the port engine this weekend and it still got to hot right off the bat. It's easy to know you have a problem when you have two engines. I don't care about the water temp just need both engines to run the same.

Were now down to pulling the boat and pulling the drive to find the zebra's which damn near have to be blocking the flow.

seapuppy · 07-20-2010, 04:44 AM

keep us all informed...really interested in what you find....

oh ..one question..have you done a compression check on the engine???....I know you probably mentioned it back in the front of the post..

SP

shrew · 07-20-2010, 01:24 PM

I haven't done a compression check since the motor was new out of the crate in July of 2009. (Unless that was directed more at Tackleshep, in which case......my bad). LOL

shrew · 07-27-2010, 08:58 PM

OK, so here is a partial update. I only have one set of manuals. I tend to keep them on the boat. So I got to the boat and began reading about the process of cleaning out the heat exchanger. Of course, the job requires a new gasket, o-ring and adhesive to reassemble once clean. None of which I had and there were no stores open for me to obtain these parts on Sunday. So, I did the only thing I could think of, I ran the boat and decided on a passive test.

I sat my wife in the engine compartment and got the boat up to 3800 RPM's I skippered and watched the temp guage while she shot the thermostat housing, heat exchanger and manifolds with a laser heat gun. I would have had her shoot the sending unit, but she couldn't get to it, see it, shoot it.

(Let's be honest, we're banging along in 2-3's at 27kts/h for over 30-45 min. while my wife is sitting IN the engine compartment taking readings, I can only ask and expect so much from her. She's a trooper and was smiling the whole time, so I consider myself lucky. Oddly, her only complaint was not the noise (her ears were ringing) or the heat, but that she couldn't sight see and enjoy the ride while she was down there. Go figure).

Thermostat Housing: 155 -161 F
HEat Exchanger : 147-155 F
Manifolds: 170-175 (One reading read up to 211, but we could never get that reading again).

For teh first half of the ride the temp. guage read 175-180F. For the remainder of the ride it was reading 190-195F. Temp. gun readings never changed. I'm thinking this is either a guage or sending unit issue. I'm goingt o try to take another ride with a buddy and see if we can get the sending unit temps. as well. I might try to have the wife operate while I take readings, but she's not crazy about that idea.

I did notice that the volt meter seems to be off. When idling it reads 11-12 (more like 11v). When running it will sometimes (frequently) read 11-12 (more like 11.5-12) and occassionally I will see it go up to 12 - 12.5) There certainly seems to be a correlation when the volt meter is reading closer to 12.5v, the temps are closer to 180F. When the volt meter reads 11-12, the temps are closer to 180-190F.

Am I loosing my mind here. These would initially seem like mutually exlusive topics. I also notice that when I hit the drive trim or trim tabs, the volt meter takes a dump and the temp guage actually goes up. I release the drive or trim tab button and the volt meter comes back up and the temps goes back down.

I'm thinking this is either a guage, sender or resistance issue. Maybe all threee. I still plan on checking the heat exchanger and I'm getting what I need this weekend. I thought this was odd and worth metioning.

seapuppy · 07-27-2010, 09:39 PM

I think what I'd look for is 2 things...1) would be are the connections in the gauges clean and tight.....that could be some of the angst your exeriencing with the gauges...2) if your volt meter is only showing between 11-12 vdc..then either the gauge again is the culprit or the alternator is weak...check the gauges again for loose or dirty wires both at the gauge and the alternator...if the symptoms persist..take the alt. off and to an auto parts store and let them test it...they can do it for free...you should be getting between 13.5-14 vdc when loaded and at rpm....
finally the temps....they all seem within normal range..but and pardon me if I can't remember..but was the impeller replaced lately??...if not...that maybe the problem....if it has been replaced...then there might be the problem with the heat exchanger or a bad temp sender.....

SP

Quote:

Originally Posted by shrew

OK, so here is a partial update. I only have one set of manuals. I tend to keep them on the boat. So I got to the boat and began reading about the process of cleaning out the heat exchanger. Of course, the job requires a new gasket, o-ring and adhesive to reassemble once clean. None of which I had and there were no stores open for me to obtain these parts on Sunday. So, I did the only thing I could think of, I ran the boat and decided on a passive test.

I sat my wife in the engine compartment and got the boat up to 3800 RPM's I skippered and watched the temp guage while she shot the thermostat housing, heat exchanger and manifolds with a laser heat gun. I would have had her shoot the sending unit, but she couldn't get to it, see it, shoot it.

(Let's be honest, we're banging along in 2-3's at 27kts/h for over 30-45 min. while my wife is sitting IN the engine compartment taking readings, I can only ask and expect so much from her. She's a trooper and was smiling the whole time, so I consider myself lucky. Oddly, her only complaint was not the noise (her ears were ringing) or the heat, but that she couldn't sight see and enjoy the ride while she was down there. Go figure).

Thermostat Housing: 155 -161 F
HEat Exchanger : 147-155 F
Manifolds: 170-175 (One reading read up to 211, but we could never get that reading again).

For teh first half of the ride the temp. guage read 175-180F. For the remainder of the ride it was reading 190-195F. Temp. gun readings never changed. I'm thinking this is either a guage or sending unit issue. I'm goingt o try to take another ride with a buddy and see if we can get the sending unit temps. as well. I might try to have the wife operate while I take readings, but she's not crazy about that idea.

I did notice that the volt meter seems to be off. When idling it reads 11-12 (more like 11v). When running it will sometimes (frequently) read 11-12 (more like 11.5-12) and occassionally I will see it go up to 12 - 12.5) There certainly seems to be a correlation when the volt meter is reading closer to 12.5v, the temps are closer to 180F. When the volt meter reads 11-12, the temps are closer to 180-190F.

Am I loosing my mind here. These would initially seem like mutually exlusive topics. I also notice that when I hit the drive trim or trim tabs, the volt meter takes a dump and the temp guage actually goes up. I release the drive or trim tab button and the volt meter comes back up and the temps goes back down.

I'm thinking this is either a guage, sender or resistance issue. Maybe all threee. I still plan on checking the heat exchanger and I'm getting what I need this weekend. I thought this was odd and worth metioning.

ss3964spd · 07-27-2010, 09:46 PM

Employ a rule often used by parents; Trust, but verify.

Which is what you just did with the IR temp gun, which shows that actual operating temps are within range. I'd be satisfied but you could go further and use a 2nd IR gun to validate the readings of the 1st. Likely not necessary.

Unless the gauge and sending unit were calibrated against a known accurate source the reading on the gauge may, or may not, be correct so the reading on the gauge is generally considered an approximation. Still useful - even if inaccurate, since they will at least display a difference from the norm.

You probably already know this; aside from the light the temp gauge has but two feeds; 12V and ground. The reading is generated by varying the ground - which is what the sender does. If you were to apply 12V and a total ground the gauge needle would peg. The sender increases/decreases the amount of ground to the gauge, thereby moving the needle (oil pressure and fuel level gauges work the same way).

What's the ground path? From the sender's own housing, into whatever it screws into, through the engine block, to the negative cable, and back to the battery. If there is corrosion anywhere thru the ground path the readings could be affected. Also, it seems to me that if there is a decrease in + voltage the ratio of + to - at the gauge will be off and the gauge could read higher for the given amount of grounding.

Get a multi meter and check the voltage reading across the + and - at the battery(s) when the engine is idling - should read somewhere in the neighborhood of 13.5 - ish. If it's only reading 11 have the alt's output tested. If that tests fine then you've a wiring issue between the alt's output and the battery. A wiring diagram will come in handy.

Dan

shrew · 07-28-2010, 01:29 PM

I put hte engine in new (out of the create) last July (2009). I didn't change the impellor because I had so few hours on the boat las year. The alternator came with the new engine. The sending unit on the new engine was not calibrated with the guage. I'll do all of the above this weekend and give a follow-up on Monday.

I really appreciate the help. Many, many thanks.

Steve

ss3964spd · 07-28-2010, 02:48 PM

Happy to help Steve, hope you get it sorted. I wouldn't have changed the impeller either and, given your IR gun readings, the impeller is not a contributor.

How you got your wife to sit in the engine compartment, with the noise and spinning belt and other bits, is a mystery to me. Can I just say "You da man"!

shrew · 07-28-2010, 09:18 PM

Quote:

Originally Posted by ss3964spd

How you got your wife to sit in the engine compartment, with the noise and spinning belt and other bits, is a mystery to me. Can I just say "You da man"!

She loves the boat and loves boating. Plus she's a bit of a tomboy. Honestly, the biggest motivator for her is for me to say "Hey, I completely understand if you are not comfortable with this, I doubt any of the other wives on the dock would be willing to do it either. I'll just see if I can get one of the guys to give me a hand. Maybe I can get someone to go out with me next weekend". That is almost certainly answered with "F that, give me that tool and tell me what you need me to do!!!"

tackleshep · 07-29-2010, 03:10 PM

Shrew, our marina is still working on my overheating issue. I'm really curious to hear what finally solves your problem. Whats the cost of a new sensor or gauge. I'm just thinking if it wasn't rediculus could you replace and see how it reads as compared to working like a dog.

Now on to much more important business......your a lucky man. I have to remind my wife where the gas tank is on ours nevermind her knowing that engines are even located under the back seats.

I have absolutely loved your "signature" and laughed about it often. But in honor of a wife who will sit in an engine compartment for a ride like that I suggest you change it for one week in honor of her.

Good luck

tackleshep · 08-05-2010, 04:54 PM

Ok have a little bit of an update on mine. The port engine is now operating a perfect temp and seems to be running right. The further investigation revealed that some waterhead replaced the impellers two years back and didn't count the pieces of the ones he pulled out. The line was full of small black pieces of plastic blocking the flow. The good news is the engine had metal grate that kept them from gettng into anything. Now were doing this all over again because now that the port engine runs long enough to get up to speed the starboard is now sending alarms so were going through the checking process again.