OMC cooling

[floattest]

This is a general question out to the OMC experts.

My engine is running great, but I'm always looking to be ahead of problems and keep a close eye on things.

I had the exchanger off when replacing my alt belt and water pump belt. Even replaced the circ pump (probably didn't need to) and repainted the pulley wheels that I had access to when the front engine mount was off.

So got all that done and during my outings this year I have taken the time to shoot the temp gun at various places on the motor to validate everything and to try to understand the accuracy of my temp guage on the dash.

Most temps taken seem to be in line with what to expect except one spot on the port riser. Measures 200+ at times during engine running, where the stbd riser in the same place may only be 140 to 160.

The temp at the thermo housing is right at 165. Some ares of the intake maifold are near 160, most less. Of course the exhaust manifolds are really hot, near 200 in most places, sometimes a little over.

Some of the issues I have battled over the years seem to be related to heat. So I'm watching that.

I took the port riser off and flused it clean with water it did have so flakes of crud in there. But after putting it all back together it still get's hotter than the stbd side.

Would any of you be concerned with your riser to elboow exhaust hose being in the 200 degree range.

FYI. the engine does not overheat.

Thanks.

​FT

 

[Lou C]

Yes I would, under normal circumstances the manifolds/risers on my '88 Cobra range from 130* on plane to 95* at idle. You have a clog somewhere or low raw water pump output.

 

[Bondo]

This is a general question out to the OMC experts.

My engine is running great, but I'm always looking to be ahead of problems and keep a close eye on things.

I had the exchanger off when replacing my alt belt and water pump belt. Even replaced the circ pump (probably didn't need to) and repainted the pulley wheels that I had access to when the front engine mount was off.

So got all that done and during my outings this year I have taken the time to shoot the temp gun at various places on the motor to validate everything and to try to understand the accuracy of my temp guage on the dash.

Most temps taken seem to be in line with what to expect except one spot on the port riser. Measures 200+ at times during engine running, where the stbd riser in the same place may only be 140 to 160.

The temp at the thermo housing is right at 165. Some ares of the intake maifold are near 160, most less. Of course the exhaust manifolds are really hot, near 200 in most places, sometimes a little over.

Some of the issues I have battled over the years seem to be related to heat. So I'm watching that.

I took the port riser off and flused it clean with water it did have so flakes of crud in there. But after putting it all back together it still get's hotter than the stbd side.

Would any of you be concerned with your riser to elboow exhaust hose being in the 200 degree range.

FYI. the engine does not overheat.

Thanks.

​FT

Ayuh,..... When did ya change the raw water impeller last,..??

It sounds like it's lackin' abit of Flow, hence the 1st place to look, is the Impeller,....

 

[Howard Sterndrive]

Most temps taken seem to be in line with what to expect except one spot on the port riser. Measures 200+ at times during engine running, where the stbd riser in the same place may only be 140 to 160.

is this on plane?

or on the trailer?

 

[floattest]

No Title

Thanks for the responses.

1. The impeller was new three years ago. Used about 80 hours per season in salt water more than half the time. The whole upper unit is new and I joined it to a new Lower unit. That little task was way more than I bargained for but I learned a ton. Little did I know that a lot of parts had to be removed, refurbed and painted before I could simply slap in the new drive. I don't recommend this unless you absolutely want to save your hull/boat motor.

2. I also think there is a restriction of some kind some where as do you guys. The heat is very localized though in that small area in the picture. The rest of that riser is about the same temp as the other one.

3. tomorrow I'm going to put it in the lake and take off the line from the outdrive and do a flow test. Also be able to see if there are Air bubbles. I fear I may need to do the water pump anyway. perhaps 3 seasons is enough. I've yet to see one of these impellers fried. But what I do notice is a lot of crud and junk ion the housing etc, when pulling it apart. the picture of the impeller housing below is with only 3 seasons on the last impeller.

4. This area gets hot on trailer, at idle or on plane.

I will say this that the motor in general will warm up about 10 degrees (on dash guage) when on long pulls. But it doesn't overheat. I can leave it at 35 mph, which is around 4K for a long time and the temp stays steady. She runs really good. I would just like it a little cooler.

 

[Bondo]

Thanks for the responses.

1. The impeller was new three years ago. Used about 80 hours per season in salt water more than half the time. The whole upper unit is new and I joined it to a new Lower unit. That little task was way more than I bargained for but I learned a ton. Little did I know that a lot of parts had to be removed, refurbed and painted before I could simply slap in the new drive. I don't recommend this unless you absolutely want to save your hull/boat motor.

2. I also think there is a restriction of some kind some where as do you guys. The heat is very localized though in that small area in the picture. The rest of that riser is about the same temp as the other one.

3. tomorrow I'm going to put it in the lake and take off the line from the outdrive and do a flow test. Also be able to see if there are Air bubbles. I fear I may need to do the water pump anyway. perhaps 3 seasons is enough. I've yet to see one of these impellers fried. But what I do notice is a lot of crud and junk ion the housing etc, when pulling it apart. the picture of the impeller housing below is with only 3 seasons on the last impeller.

4. This area gets hot on trailer, at idle or on plane.

I will say this that the motor in general will warm up about 10 degrees (on dash guage) when on long pulls. But it doesn't overheat. I can leave it at 35 mph, which is around 4K for a long time and the temp stays steady. She runs really good. I would just like it a little cooler.

Ayuh,..... I'd start There,....

 

[southkogs]

^^^ agreed.

 

[Lou C]

Is this a full closed system (manifolds on the antifreeze circuit)? If so that does place a big load on the heat exchanger, when was the last time it was cleaned out?
the problem you have is probably one, or a combination of these 3 things:
1) lower than needed raw water flow
2) slightly clogged exchanger
3) clogged riser

 

[floattest]

Thanks Lou. Yes, full closed. raw water thru exchanger and riser only.

I've had both the ps cooler and heat exchanger off and flushed out within the last year. Heat exchanger was off and getting flushed a couple weeks ago. same with the port riser.

The company that made the heat exchanger will do a clean inspect for 175, or replace for 1500. Yowza!

So anyway that's why I had it off and cleaned it out, it's in really good shape. I always flush it after salt water with "salt-away"

I think you are on to something with item 1. I didn't get a chance to test this past weekend but that is my next step. flow test.

I may be in line for a new SHT. If my suspicion is correct I may have assembled it a few years back without the big o-ring that goes around the impeller housing. I can't find evidence that I put it in!

And if my suspicion is doubly correct the pump will still work without it, but less efficiently.

I remember the first time I did this pump replacement about 6 years ago that I couldn't figure out where that big o-ring goes. It didn't fit anywhere I could see. Then, recently I was messing around with my spare parts and thinking on the heat problem and it dawned on me as I was looking at a different picture of the upper gearbox parts. Right there obvious as can be is the big o-ring on the outside of the pump housing.

Hopefully today or tomorrow I will test and confirm for you all.

good gravy, stand by for news

 

[floattest]

No Title

ok, here's the news.

I had enough doubt about the last water pump install that I just took it apart to inspect/repair. Didn't do a flow test.

So it was a good thing I did. For some reason the pump shaft looks like it got very hot. Never saw this before.

I did discover that the big o-ring around the pump housing was in place as required. The last installer, used RTV around the top end of the pump shaft and around the shaft where it goes through the impeller plate that's not right. maybe a good trick, tho?

Also the shaft seal on the top of the snap ring was worn and cut in half. I couldn't even discover the old snap ring, maybe it wasn't there in the first place.

The impeller and pump were both in good condition.

I put it all back together doing it by the OEM manual every step.

No sealers on the the impeller plate at all. Only sealing compound on the top side of the pump housing. Sealing compound was used on the o-ring and the splined seal and the snap ring, just for some added corrosion resistance. new o-ring in the bottom of the shaft and of course a ton of grease. permatex 2 on the pump screws and the exhaust housing bolts.

The reason I showed the picture of the swivel bearing housing is because the grease looks like it got boiled out a little. It makes sense with the way the shaft looks. Another theory for the way the grease looks in that bearing housing is maybe one of the seals is leaking and hurting the pump efficiency. The seals looked intact, I put new grease in that part and gave it a few more strokes once it was together.

So before I fired it up I disconnected the hose that goes from the intermediate to the heat exchanger and I blasted the hose backwards into the line that feeds the risers. It flowed out with no obstructions, that was going thru the heat exchanger and the ps oil cooler, that line is clear.

Earlier I mention that I had the port riser off at the beginning of this thread and flushed it out real good. It's still on the list of potential problems though.

Fired her up and of course she ran great, heated it up and same results. According to the dash guage it's the same temp as before.

Heat gun at key spots say the same. I think temps were a tiny bit lower on the engine water passages common to the intake manifold. The temps at 90 percent of the risers both sides are pretty good, no more than 130 or so.

But the problem I'm trying to fix is a weird hot spot on the top aft of the port riser.

I did a flow test. got about 1.5 gallons in 10 seconds.

I'm thinking of taking the elbow and exhaust pipes off to look again at the exhaust flapper. Can they get stuck and restrict exhaust?

Also, that port riser may need to be replaced altogether if it has developed a restriction from corrosion. It didn't look bad though. I don't have pics of it.

Any other suggestions? thanks folks.

FT out.

 

[floattest]

Here's an update:

I wanted to clarify from before that the water pump was replaced with all new parts. It seems to be pumping fine.

Since the heat was still there I decided to replace the port riser anyway.

On the trailer it stayed cool, a little cooler than before. Going to get on plane today and see what it looks like. I will take some heat measurements.

Also got in there to take a look at the flapper while it was apart. no restrictions, operates freely, material intact. that's good.

ON the trailer:
The port riser is cooler than before. On the top aft the hose not too hot to touch. The Stbd riser is now warmer than the port at that same loacation. Also to clarify the only area that was overly warm just like the port was on the top/aft at the 3 inch hose connection and on top of the hose itself.

Looks like I may be looking too hard for a problem.

I can see now that I will probably replace the stb riser soon and make sure I have good and basically equal flowage thru both risers.

I added an overflow tank to the heat exchanger system. I learned that this was standard for the 260 OMC that came with closed cooling. So figured I would upgrade mine with the same thing. more fluid should equal more cooling capcity

If possible I would still like to know what anyone might think about the pump shaft? It sure looks like it got hot and I'm not sure how to read it. pump weakness or restricted flow?

I believe that I have really improved the cooling system now. stand by for a report.

Thanks

 

[floattest]

Got out and on plane.

The port riser is good now, feels cooler. Did not change the stbd riser, it's a little warmer than the port.

I still think there is something not right. It (engine overall) still seems to run hot.

I wasn't able to get any temp measurements with the infered, but from the dash gage, I do know it was Not running cooler than before.

It ran good for over three hours. didn't overheat. temp stayed steady at 1K, got slightly warmer at 3K.

I'm going to install a clear hose in the feed line and examine for air bubbles while on the water.

My previously reported 1.5 gallons in 10 seconds may have been influenced by my garden hose pressure. I want to get a volume reading while sitting at the dock and also see the water going to the exchanger.

Any suggestions at all would be greatly appreciated.

 

[Idlespeedonly]

I dont have much to add since it looks as though everything has been covered.
But it really shows you take great care of your stuff. That motor and drive is cleaner than most of the newer boat I have seen.

 

[Lou C]

Your raw water flow test should not be done on the water hose, that assists the impeller to push water through the system. I would put the boat in the water, tie up at the dock, remove the hose from the impeller to the heat exchanger and briefly start the engine, then measure output. Thats the only way to really find out if the impeller is pumping enough water.

 

[floattest]

Thanks for the comments idlespeed and Lou. Yes, that is the plan. put on the clear hose, put the boat in the water and do a flow/time test and a visual test of water flow at idle and on plane.

I don't think the problem is in the pump itself. It's all new. I'm sure there is no restriction in the risers, covered that possibility.

I'm wondering if the seals common to the swivel bearing may be letting in some air.

Anyway, hopefully will get to do this test sometime this week and report.

Thanks,
FT

 

[floattest]

Got out last Saturday. Intention to test as above. Put a clear line on the exit from heat exchanger to entrance of t splitter that feeds the risers.

At idle in the water there were a few bubbles at first but within a few seconds it was pumping clean and strong.

Disconnected the same hose and ran it for 10 seconds and it pumped about 1.5 gallons in that time. I think that is good per spec.

Oh, forgot to add, before I launched I pumped a half dozen shots of grease in the swivel bearing just for good measure seeing how I just had it apart recently when I changed the water pump.

I was out for over 3 hours, and it stayed reasonably cool the whole time.

I did quite a bit of running at plane speeds anywere from 25 to 38. The only thing that still bugs me is that it warms about 10 degrees (judgeing by the gage) when at plane for any length of time.

Since I was solo I was not able to look at the clear hose when on plane. That's too bad, because maybe at high rpms, there is a seal that starts sucking air. I'll try this test next time I got a crew member on board.

Anyway, I'm ready to put this cooling situation to bed.

The replaced riser, the new pump, the flushed heat exchanger, cleaned, sanded and painted the pulleys, new belts, new circ pump etc. is about all I can do to make sure she runs cool.

The things I was hoping for an opinion form another OMC mechanic on was the picture of the pump shaft I took out. Anybody got a clue why it looks all blued? And the other thing I might add is that this lower unit is essentially a new GLM lower unit from Crowley marine. I noticed it has all the same exhaust ports and such, but the water pickup is designed a little different than the stock lower and the other thing I noticed that is different is that it doesn't have a pee hole on the side like my old lower unit. kinda weird, don't really think if it matters though. GLM sells these for cobra or stringer (mech shift) I always check for flow at the pee holes that come out onto the ball gears when I'm on the garden hose.

Anyways, thanks for listening to my ramblings
enjoy the water
​FT

 

[800wildcat]

Another thing to keep in mind when testing and comparing one side's temps to the other is that the water flow from each side does not mix together in the intake manifold and flow out through the thermostat housing together (as you would expect). Whichever side is hotter will overcome the other side and will flow all from that side until it becomes cooler than the other, then the other side will flow. Remember that hotter equals higher pressure which is why this phenomena occurs. The two sides' flow trades back and forth taking turns (whichever is hottest flows). This may only have an impact if you are checking first one side and then the other quickly. If you take averages over time, it would be a moot point.