Heat problem on 525's,

[PARADOX]

This heating thing is annoying. Just like many of you, now mine is heating up now. Only the port side. Port side headers hotter than starboard on port motor. Usual temp is around 140. it got to 175 +- at high RPM's, going back to 3000 RPM... temp goes back to 145+-
Impeller is new, no blockage in any of the hoses that I can see. Back flushed the system. Closed cooling, heat exchangers are clean.
Ran a garden hose to several of the pipes/hoses. Good flow. If I by pass the impeller intake line, and directly hook up the hose to the impeller housing, there is smaller water flow coming out of the port exhaust tip.
Interior blockage on block? Thermostat? circulating pump?
It only runs warmer at above 4000 RPM's, but the CMI headers are warmer then the starboard motor.
Starboard motor is fine.

I'm lost.

HELP!!.
Thx

P

 

[Raylar]

It seems quite sad and a poor commentary on Mercury Racing that they can sell their expensive engines and not help customers like this with good technical support after the sale with customer questions and problems!
Come on Merc-get it together for your good customers! they put you where you're at!

Well, here goes Raylar's hopeful help contribution!
First, remove the loop hose from the header collector to the tip on the tip end and look to see if there is any blockage or debris in the restrictor plug in the inlet fitting on the tip. Also take off the bypass hose from the lower water feed rail end on the header and check the restrictor plug in the tip entrance fitting for blockage. Because these restrictor plugs ahave fairly small orfices it does not take much to plug them. The raw water feeds out of the headers on the 525's and others are fitted with restrictors to slow the raw water exiting so it has more time to build pressure and cool the exchanger and header without blowing thru the raw water system so quickly.

Also remember that if you are boating in sandy or debris laden water the debris especially sand can go thru your strainers if you have them and start building up in the bottom of the headers in some cases and lead to overheating and restrictive blockage at the header. If you boat in sandy ares and beach your boat or stir up the bottom in shallow areas, install sand strainer inserts or sand strainers on your boat.

A scan tool here will also be helpful becuase if raw water flow is being restricted anywhere in the raw system the water pressure should be high or if the raw pump is not pumping adequately the pressure should be lower than specified at certain rpms in the 525 service manual.

I hope that most of you performance boaters realize that with the expensive investment you have in your boats and engines you should have either (1) a good Merc qualified service shop and technician, or (2) a scan tool or laptop software, and always (3) a service manual for your particular engines.
If you try and troubleshoot your own engines and problems with none of the above, you kidding yourself and most likely frustrating yourself and wasting valuable boating time and money guessing.

Remember, every problem has a cause and solution, and if you work smarter not harder you will spend more enjoyable time boating and less time cussing your power and systems.

As for Mercury Marine, who knows, its hard to teach an "Old Dawg" new tricks??

Best Regards,
Ray @ Raylar

 

[PARADOX]

Thanks Ray.
Did most what you recommended. All tubes, hoses and restrictor holes are clear.
For some reason this is a re-accuring problem. Some time ago the same motor had some heating issues. Almost like random. Never got too hot, just "warm". I have to check the thermostat.
However your comment RE; Merc is right on to the point. Called them many times. (Just talked to them yesterday), While he motors were under warranty, service and "help" was OK. After warranty.. (take a hike Mr. Mercowner) and take it to a marina.
The problem, there are only a few Merc. Service guys around my area. The place I take the boat is OK, the OWNER is a good mech, and certified by Merc. but his mechanics.. ? Wel.... I really don't even want them to go near the boat anymore.
I don't have a scanner, and would not mind buying one. Don't know where to get one.
But thank YOU, Ray for being around here for us and helping many of us out with your answers, comments and input.
P

 

[Ratickle]

Chris has said many times, don't always assume new parts are good parts. Did this start when you changed to the new impellor?????

Yank the thermo completely out and run it, have the thermo with you to put back in.

You said closed cooling, could be different issues than raw water issues. I'm not familiar enough with the plumbing on that to tell you what else to check.

 

[txriverrat2001]

If it's running hotter temp ONLY at higher RPM's - have you checked the the transom hose at the rear of the engine?? Or do you have thru hull pick ups?? If your picking up through the drive you may want to check for a collapsed hose. Remove the neck if possible and check for corrosion built up around the hose. If you have ANY trouble removing the two bolts holding the neck on - stop there. Once you snap them off you can plan on pulling the motor to get them out. And if they are stuck - that's a hint and a half that you have an issue there.

 

[cigdaze]

Peter, Like txriverrat suggested, have you checked your drive, transom plate and inlet hoses?
http://www.seriousoffshore.com/forums/showthread.php?t=7931&highlight=overheat

 

[PARADOX]

Weard thing. A few months ago, port motor, port CMI header got hot. OK, replaced hoses, impeller, probobly had some blockage. Motor never got warmer or hot. Raw water issues. Fixed, cleand out, blockage out, running good for a while. Destin run. no problems. Half way in the run at Sarasota, I hit it a little got to 5000 + RPM... problem. Open seas, so I doubt I picked up something. Impeller is still good and "soft".
It seems that the raw water does not circulate fast enough or there is not "enough" water circulating through the system. T. Stat is my next try. (I got to find it first. lol )
When I "feeL' the water temp. at the exhaust tip... port is warmer for sure.
I got to find my Turkey baking thermometer and check exect reading.

 

[PARADOX]

Peter, Like txriverrat suggested, have you checked your drive, transom plate and inlet hoses?
http://www.seriousoffshore.com/forums/showthread.php?t=7931&highlight=overheat

Inlet hose etc. is good. The problem exist even when I by pass the transom intake hose and hook up garden hose direct to the impeller.
Exit hose from impeller to block is also clean.
I will check the thermostat today, and then remove erverything.. blow air in the system to "dry" any seaweed I might have inside the block somewhere. I can't think of anything else, but the circulating water pump, and I hope I don't have to mess with that.

 

[MOBILEMERCMAN]

You said heat exchanger is clean. Did you actually pull the end caps and look?

I don't believe it is possible to trouble shoot overheating with a garden hose. Not near enough flow to give real info.

 

[PARADOX]

You said heat exchanger is clean. Did you actually pull the end caps and look?

I don't believe it is possible to trouble shoot overheating with a garden hose. Not near enough flow to give real info.

Thanks Jim, but yes. I pulled off the end cap. The little holes/ports and all interior looked clean. Nothnig inside.
The "garden" hose i use is at the warehouse 1 1/4" high volume and preasure for truck washing. It should have enough volume and preassure. Probobly more then the impeller. The outflow of water at the tail pipe tips is better when I by passed the impeller and hooked the hose up directly to the "outflow" hose on the block. About the same stream of water coming out from both tail pipes. When I use the impellers, with the garden hose or with a "tub" and drives inside the tub, port exhaust tip have less water outflow.
Impeller is good, Just replaced it again, same issues. The port headers are furthest from the impeller so Merc said it's normal to have a bit less outflow.

It seems that all passages are clear of blockage.
Didn't check the thermostat yet, I need to get some coolant to replace what I will loose getting to it.
But.
Could the "oil coolant" system cause the engine to run warmer? I didn't pull the coolant heat exhanger end cap off. (rear of the motors) I didn't know what I'm getting into. Would I loose some oil? or it's just like the front and water only.? Oil pres. is good.
Based on all the BS trials and errors, it seems that either something inside the engine is blocked? thermostat is stuck... closed cooling heats up the sea water, therfore headers are warmer, and outflow water on port side is warmer... or circulating pump not circlulates "antifreeze" fast enough. ??

Next attempt. I will hook up the "garden" hose to the outflow tube at the impeller, (bypassing the impeller, removing it first)and see what temps I'm getting. I guess it would be OK to run the motors with out the impeller and housing, as long as there is water flow. Stop me if I'm wrong.
BTW. at low RPM's there is no engine temp issue, but the headers are definetly warmer then Starboard side. Headers are "hot" to the tuch, not just warm as on Starboard. So I'm thinking lack of water flow somehow.

Thx
P

 

[Raylar]

Paradox:

Finding gremlins in marine performance engine systems can be a hair puller most of the time, but thanks to the wonderful world of electronics, the process gets a little simpler.

Another trick you might want to try if the problem is at the header is take the hose of of the top of the header, remove the inlet water hose at the bottom of the header feed rail and pinch off or plug the bypass hose at the rear of the water feed rail and then hook up a hose to the top of the header and backflush thru the header and out the raw water feed rail at the bottom. this will generally flush out debris and sand from the header and may help clear a clogged passage in the CMI header. Does not hurt to do both headers even though you only have a problem on one side either.

You can purchase the Diacom hand held scanner or the same in laptop software from Rinda Technologies in Chicago. Should be about $400-450 for either version and it will help pinpoint what has happened with the engine now and in the past from history in the ECM and you will be able to read such things as water pressures at various rpms, exhaust header coolant temperature and engine coolant temperatures and then cross reference these to the Merc HP525 serive manual and it should help in tracing down why the port side is running to warm. The scanners are hugely important in finding trouble codes and monitoring the Merc engine for "Guardiian" modes, which are engine protection and wallet protection controls for your expensive engine! Good Luck with the "Sherlock Holmes" troubleshooting, but there is a solution, the problem just has to be found first.

Best Regards,
Ray @ Raylar

 

[PARADOX]

Thanks Ray..I looked at the Rinda Tech. site and I will order the software.
Just hooked up the "garden" hose to the outflow host at the impeller. Removed the impeller and put the housing back for the fuel pump and pully support. Ran it for a while, water flow from both tail pipes was good. headers were warm to the touch, but not hot.
The right side of the heat exchanger did get war or hot to the touch but not "very" warm but I don't know what "very warm is. THe circulating pump and the large water hose also got warm / hot, but it may be OK. I'm not sure how warm / hot it should or could get. Will run the starboard motor and compare in the AM.
The "antifreeze" in the closed cooling system did not seem to move or go up or down.
Hardly seen even a ripple in it, so it may not be circulating, cloged somewhere? or the thermostat is shot.? I have to find some of this pink stuff to check the T stat, and work on the closed cooling stuff. Sea water system seems clear.

The Gremlin is still loose, and I'm getting "balder". Don't have much hair to spare, but more Gremlin hunting yet to come.

 

[PARADOX]

Update, and still have the problem.
After a lot of flushing and cleaning, new impeller, took the boat for a test drive Saturday. After 10-15 minutes temp was creeping up. At higher RPM's still get's to 170 + and I can tell that there is some "steam" coming out from the tips. headers are definetly hotter and engine is hotter also. There is no known restriction in any hoses, headers etc.
Can the oil cooler not work well? heat up the oil then heat up the motor/water?
T. Stat stuck? heating up motor, thus heating up raw water - heating up motor and headers? I also lost some RPM's could "strain" on the motor from outdrive or somethig internal cause temp rise?
I'm still lost with this.

 

[35 Lightning]

I had this same thing 2 years ago on my other boat w/496 mag HO, engine getting to 170 over 3500 rpm, exhaust getting hot, eng. sensors started derating rpm's, stop, idle for 2 minutes it ran good for short while, or at slow rpm, after 3 weeks looking for anything, calling mechanics, I found the problem by accident, the serpintine belt wears and puts off a very fine dust, the lower 1/2 of my air intake screen was very dirty, restricting airflow, i cleaned with carb. cleaner, full of black dust, ran great after cleaning, hope this helps, good luck.

 

[PARADOX]

THanks Lightning.

I rotate the intake screen once in a while. Seems pretty clear, but I will take a closer look this weekend.

Thx

P

 

[mbam]

Have you checked the inlet at the gimbal housing like txriverrat said? Have you actually pulled the inlet off and looked? This is VERY common and VERY often overlooked. The aluminum corrodes and constricts the hose from the outside. Physical inspection is required- all of the time!! And yes if you break the bolts you will be pulling the engine.

Thermostat will not change water flow through the headers; it is on the closed loop side of the heat exchanger. Low volume & high temp of outlet water = reduced flow - period.

Yes check the oil cooler at rear of engine that is the first stop after sea pump, well maybe the power steering is first my memory is shot, in any case whatever is first after the sea pump inspect carefully. If needed pull the ends or hose off it and look, use a light and a mirror if needed. You will not lose any oil as the end caps are on the seawater side. If you have ever lost impeller blades this is where they will wind up. Don’t take anything for granted just because you have pushed water or air through it.

I don’t know if this is an issue on the Merc stuff, but I know that back in the day when I had closed cooling on my Cigarette, and now with my Volvo diesels the heat exchangers develop a mineral build up on the raw water side. Periodic removal of the deposits is required (every couple of years on the Volvo’s). I do it chemically with Barnacle Buster or Lyme Away.

The most useful tool you can have is one of those IR laser deals, that way you can poke around and compare temps with real numbers.

Good Luck !!

 

[glassdave]

i had a similar problem with one of the 525's in the Donzi. Flucuating temp issue, turned out to be a loose hose and was pulling air into the system. The hose was barley loose to but that was it and it all started when i put in a new impeller. Make sure you run the entire suction side and check for even the slightest leak. good luck

(i didnt read the whole post in case this was already suggested )

 

[mbam]

UPDATE FROM LAST POST - I just looked at the water flow and the cool fuel is first - look there for seaweed/impeller bits, etc. Also check what Glasdave said.

 

[PARADOX]

UPDATE FROM LAST POST - I just looked at the water flow and the cool fuel is first - look there for seaweed/impeller bits, etc. Also check what Glasdave said.

Thanks guys. THe hoses are tight, most are double clamped.
"oil cooler" ports are clean, PS cooler .. clean,, cool fuel cooler ... clean..
All hoses in bilge are good.

I bought some additional suction hose and will switch outdrive raw water supply source from port to starboard. If Port motor still heats up using starboard outdrive source, then it's nothing in the gimble area. ( I will check anyway, but I'm trying to pin point the problem)
After a lot of checking, I gues it might be the thermostat. Motor heats up,, then heats up raw water so the headers get too hot. I hope all it is a TStat.

Thanks for the input... keep them coming. I have soem good news too. The Formula is almost done. New motor is running good. All I have to do is put the outdrive back in. I hate to be "beached", got to get on the water soon or I'll bust.

 

[mbam]

If the thermostat is closed the engine is hot becuase the engine water is not being circulated through the heat exchanger. Actualy the discharge water would be cooler.

When your car is warming up you will notice the radiator is cold until the T stat opens.