Update: 5.7L MC Bluewater FWC temp creeping high on plane, read tons of posts.

[rothfm]

I’m an outboard guy (on the Iboats OMC forum) trying to help someone with a new-to-him boat. Although I’m a good outboard mech, not entirely savvy on these inboards yet, but getting there. Been reading posts all day-still looking for advice

I’ll write boat/engine spec’s below, and below that my IR temp readings and observations. Also attached is a copy of the water flow-diagram with some of my notes written on it.

Here goes:

• 1995 Searay Weekender 300 (30&#146
• Dual 1995 5.7L Bluewater MC inboards, full FWC and V-drives
• We have Maint records from 2007 from Past Owner, always serviced at same marine-very well maintained.
• Risers and mani’s done just about 5yrs ago. We are planning on doing them soon as they are due.
• Raw water impeller done 2013
• Unknown replacement date on the Circulation pump impeller.

Engine in question runs fine at idle and slow speeds, guage showing same as good motor at 160-170. We then do test runs at 3k rpm, and Stbd side slowely rises to around 190 after a good 5 min run. Slow down and it drops back to 160-170. No alarms.

Observations:

• Plenty of comparative(with good engine) water flow out the exhausts at all speeds.
• All IR gun temp readings match good side at idle and slow speeds.
• Only detectable are of difference is directly on the t-stat housing. Bad side at 3krpm shows 180-194. Good motor solid at 159-166. All other hoses, risers, manifolds, heat exchanger ends-all compare to the good engine.
• Strainers are clear.
• All fluids fresh and topped.
• No visible signs(Leaks, air in coolant etc&#133.

My thoughts:

• Even though I don’t see it, possibly the exchanger output to Circ Pump is warmer than it should be, elevating the temps throught the process (again, I don’t see any marked difference to good engine). Exchanger efficiency issue?
• Possibly T-stat not opening fully restricting flow and increasing temp(provided input to Recirc pump at norm temp).
• Recirc pump impeller causing a lack of volume(again, not seeing much difference in all other areas).

Questions

• Riser input temps from the exchanger is cool(same on both engines) and risers are cool, hardly warm at all—is this normal?
• If my temps are elevated, wouldn’t I see that on the manifolds…all 4 are the same temp at all speeds.

Sorry this is so long, I want to be clear and provide concise information. Thanks In advance to those that have input.

 

[rothfm]

Oh, and it never seems to go much beyone 190-195 but we slow it down to cool back to 160-170

Thoughts anyone?


Thanks
Mark

 

[NHGuy]

Good job with the notes Mr.Outboard. It appears that the water outlet temp from the t stat is your main issue. First off. is the coolant level and mixture correct on that motor? No leaks?
If so proceed by inspecting the thermostat housing for junk, I'd just change the thermostat anyway, they don't cost much compared to what they protect. You need to use one that's specifically for a Mercruiser as they have a continuity rivet in the outer ring. Without that grounding piece the temp gauge gets wrong inputs. You could also swap the known good one from the other engine too.

 

[rothfm]

Thanks NHGuy,

Yes, all fluids are topped and correct/Fresh with no leaks. I wanted to spend the day testing, and observing before going at it...But for sure the T-stat will done shortly...My first suspicion.

In General are the Manifold surfaces hot, while the Risers remain cool on this setup. At 3k all 4 Mani's run 180-200 and the riser Elbows are cool at about 90degrees I believe. Sound normal?

 

[NHGuy]

The mani's get the engine coolant last before it goes back through the heat exchanger, Your engine is a little hot to start with so no surprise there. Since both engines mani's are about the same temp I wouldn't worry too much about that. The reason the risers aren't as hot is cause they get warm water from the heat exchanger, not hot coolant from the engine coolant circuit. The mani's are right outside the combustion chambers, CC temps are very high.
The cooling water just keeps on pumping, so the risers don't get as warm.
At 3K that motor is making bunches of torque and heat. We just need to get rid of the 2nd part.

 

[RCAnderson]

I am chasing a sort of similar problem on my own new-to-me engine. Since yours was known to be running well previously, we have a good place to start. NHGuy is correct, the risers should be cool to the touch, as they see the raw water that is output by the heat exchanger after doing it's job. If you can't put your hand on the riser, you have raw water flow problems (or heat exchanger problems, more about that in a bit).

I would not suspect your manifolds at all, for a closed system fresh water cooled engine 5 years is not long at all. There is no salt water inside the manifold at any time, only engine coolant, so no rusting issues.

It is getting close to being due for risers, but as I stated above, if they are flowing fine they will be cool to the touch. The risk is that they rot between the exhaust passage and the raw water passage, thus allowing raw water to potentially enter the exhaust passage on the manifold, and then the combustion chamber.

The engine circulation pumps are not usually a problem, as they run in engine coolant, not raw water. It probably still has the bronze impeller though. I would not suspect this of causing trouble at all. If it's not leaking, leave it alone.

If this is an 'all of a sudden' type problem, then I would suspect the thermostat sticking, or the zinc anode breaking off. If not, I would suspect the heat exchanger should be hot tanked and pressure tested. Heat exchangers are typically a bit over designed, to account for the gradual degradation of efficiency due to build up of crud, crap, and corruption.

One check for this is to get your IR temp gun, and check the temp of the heat exchanger raw water inflow, raw water outflow, and then check heat exchanger engine coolant inflow and outflow.

If you have a large increase in temp between your raw water in and your raw water out, the raw water is moving too slowly through the exchanger, and has more time to heat up.If the increase is not large at all, suspect heat exchanger efficiency. About 30 plus or minus 10 degrees or so difference is good.

If you have a large decrease in engine coolant temp in and out, the engine coolant is moving too slowly. If the temp change is not very large, suspect the heat exchanger efficiency, or the raw water flow. With a full system 40 degrees plus or minus 10 degrees difference is good.

Another thing to check is the zinc anode that is on most heat exchangers. This will look from the outside like a plug. Unthread it, and it is a pencil anode. These of course are meant to erode, but they can break off and get stuck in one of the flow passages of the system.

I hesitate to mention it, but since I am at that point troubleshooting my own engine, you may have a blown head gasket. It's unlikely, but if the gasket blows, you are either short circuiting your engine cooling system, so to speak, or you are allowing combustion pressure (exhaust) into your cooling system. This will usually happen only under load when the engine is hot, making it a bugger to track down.

So to sum it all up, get the heat exchanger off and over to a rad shop, and pull the thermostat and at least check it, and if you do replace it, check the replacement before you put it in.

Hope this helps.

 

[rothfm]

Thanks RCAnderson for taking the time....Good points especially the IN/out comparisons at the exchanger. I'm going to take another close look at those readings as compared to the good engine, and look at that anode you mentioned.

Will get to marine this week to put in a new Tstat too. There is an automotive test kit to test Coolant for the presence of exhaust gases. I'll look into that to rule out a Head gasket issue.

Will report back when I now more

Thanks for the responses thus far. Appreciated.

 

[rothfm]

Update:
Removed the suspect Tstat and was surprised to find a 140deg in there. I thought if anything, It would run cooler. I put in the 160 listed in my manual and research shows should be in there. If I had another gasket I’d love to pull the one on the good engine to see whats in there.

Question: My kit had all the gaskets, but my housing would only accept one, which is Oval with the square side porton, NOT the plain oval one, with the grommets. And I couldn’t use the Cork as it would sit up high and the housing would not seal. Is this correct? This was what it had when taken apart.

The parts counter guy suggested I get the plastic sleeve and brass type ring also in case needed. It didnt have either of these in the housing. It was just the stat sitting on the lower housing, gasket over that, then the top housing/cover and bolts. Very simple.

In this thread is a diagram of my system and Tstat housing. It has only incoming from exchanger, and 2 outlets to the risers.

 

[rothfm]

Ahhh, for illustration purposes, found this kit on ebay that shows what my housing and gasket looks looks like.

This doesnt ahow any sleeve or ring, i got them but no way wither would or the cork seal.

Parts diagram doesnt show anything but housing, thermo and gasket with the square bump out

Hoping someone can concur i got it right. The old one was like this also. Seems right juat checking.

 

[rothfm]

Oops, the link:

http://m.ebay.com/itm/121466428937

 

[skippy2235]

I found that after 3 T-stats, I needed to get the High Flow MR Gasket Racing 160 deg. $25
that solved my issues and temp runs perfect.

 

[rothfm]

skippy, thanks for The reply could you elaborate?

Would you know what that the part number/application compatibility is? what's different about it? and if it would match my housing that's depicted on the eBay link picture in above post.

Appreciated

 

[skippy2235]

Yes this will fit.
Get this from a good parts store like Napa, carquest ect. [h=1]Mr. Gasket 4363 Performance Thermostat[/h]

http://www.amazon.com/gp/aw/d/B000CM...B2L&ref=plSrch

 

[FreeBeeTony]

I have a similar problem and was thinking it might be my risers as this is their 4th season.
Just looked at my repair records and last time I replaced them they also has 4 seasons on them and they looked great.
Now I'm 2nd guessing my current problem which is very similar to this.

 

[rothfm]

Thanks FreeBee.....

Was hoping someone could look at that Ebay link I provided (pic is identical to my setup) and tell me if the simple single gasket I put in is correct..This setup will not accept the sleeve or brass ring or the cork gasket. See above ebay link, IF someone can verify this setup is just the oval/with square bump out, and the Tstat--I'd be in your debt. Seems to match the Parts book too.


Ive thought about the Raw water side also...In the 5.7 full FWC system, the raw water intake goes thru the belt driven pump-to the exchanger>out of the exchanger>direct to the risers>and out the mufflers with the exhaust.

So I suppose this could be a volume/flow issue from the start (raw intake), if I saw higher temps along that route. OR raw water to Coolant side inadequate heat exchange, due to an efficiency problem with the exchanger. Resulting in initial higher temps on the Fresh water side. I just dont see it. The only place I can see a marked difference was at the Tstat housing.

Granted If this continues I'm going to have to re-measure precisely and record the readings on a chart.
RCANDERSON in post above brought up some good points about Raw and Fresh IN/OUT temp differences-I will look at closer next opportunity if need be.

If it was on the raw water side, I'd expect hot risers...Risers are cool, and I mean real cool 90degrees at plane, and plenty of volume coming out the exhaust ports, as compared to the good engine. I dont believe this is on the Raw side due to the above. On the Fresh side, all 4 mani's are comparable too.

New Stat is in (found a 140 in there).


Boat will be tested Friday and I will report back. My plan if the issue still remains:

*Open exchanger to clean, check.
*pull Raw hose after pump to verify flow, on a short idle.
*remove all hoses looking for restrictions, including trans cooler.
*Test for presence of exhaust gases in Coolant.

 

[FreeBeeTony]

I'm interested to know if the high performance t-stat shows any improvement.
I will also try the measure the temp on my risers.

 

[rothfm]

New oem stat just put in. Not ruling out trying one of those hi flows at some point however. Let you know if i do.

Boat is remote from me but testing tomorrow with new stat.

If you run thru your temps again, RCAnderson has some tips above about exchanger inlet and outlet temps on both fresh and coolant side.

Id be curious what you see for numbers/differences as far as exchanger efficiency goes.

Will update when i know more.

 

[rothfm]

More update: Bit lengthy to be clear.

Spent day at boat again….Summary of issue: One 5.7 FWC runs warmer on plane only, compared to other engine. New 160 deg stat, checking with IR gun, Same results. Its New to owner (Brother), meticulous repair history with records. Exchangers, Riser, manifolds and hoses down within 5 yrs.
Stuff done today:

• Remove Raw water pump output hose to verify flow-Tons.
• Remove in/out hoses to Transcooler. Looked fine, but flushed it.
• Open Heat Exchanger, shine light thru and verify all tubes clear. Use brush and blow out with air.
• Remove all Raw side hoses, all fine and clear.
• Close up system. Use product called Barnicle Buster. From bucket, allow 5gals to be sucked into system from raw intake-Shut down and let sit for 1hr per directions. On restart/flush saw murky brown come out awhile until it ran clear. It did in-fact do some cleaning as advertised.
• Swapped Temp guage with other engine. (not sender).
• Coolant is fresh and nice bright-green. No appearance of exhaust gasses in it.

Retesting at idle, all temps in all areas of system match other engine…160-170. At Fast idle all good. 2500-3000:—SAME ISSUE--—Temp on Stdbd slowly climbs on "GUAGE" to appx 190+, while the Port may get to 175-180.

The Guage is not really graduated, so Its an approximation. Re-shoot all Temps around system with IR gun. Raw in/out and Coolant in/out show comparative differences of 30-40 degrees which I like. The exchanger is doing its job.

About the only difference I see is at the Tstat housing. This time, temps are even closer now to the “good” Engine. Good side 161-165, suspect side 168-178 ON-PLANE. Both Engines Manifolds, risers, hoses, exchangers —seem to compare.

I realized the “good” Engine shoots a line off the engine, 20ft’ round-trip to the Hot water heater up the boat. SO, I’m guessing this would cool water off a little and explain some of the difference?

I’m convinced the motor is clean in/out.. I didn’t swap senders yet (too hot). Some people here, and at the dock say without a history, one doesn’t know the running characteristics, and this Temp is probably ok-to keep an eye on it and let it run?

***Are we being too anal about this difference of possibly 10-15 degrees? No pings, knocks, alarms. Really seems to run well!

 

[rothfm]

I will be swapping the sender just for Grins soon.

 

[skippy2235]

Like I said, mine did the same thing. Solved it with Mr gasket thermostat.