Cooling Intake line issue - What next?

[ConchPirate]

VP 5.0GXi-E/SX-M outdrive

Due to an overheating issue (port engine only @ idle/low speeds) with a brand new water pump installed I took advantage in another post here to narrow down the problem to the water intake line problem. I connected the port engine pump intake to the STBD engine supply line and the engine ran with zero overheating issue at all (video link with IR gun measurements available). The manifolds and risers never got above 120F. Let it sit dockside at idle for almost 45 minutes and it never did overheat.

Reconnect the port engine normal water intake line and the manifolds seem to overheat (going to temps of 150 and climbing fast) within 3 minutes! Yikes. Because of the suggestions of cracked hose fittings and potential of drawing in air, I pulled the pump intake line and connected a garden hose directly into the intake line to backflush. I'm thinking that if air can get in (cracked fitting/loose clamps as suggested) then water under pressure can get out. While the water was back flushing I did some video watching for leaks in areas other than the water intake ports on the lower unit. Didn't see any other leaks along the line either inside or outside. I also ran the same test on the STBD engine line to compare output flow and it doesn't seem to be significantly different. Perhaps someone here sees a difference I don't in the video links.

Based on the picture of a new oil cooler I cant see that it would become so blocked up that it would restrict the water flow that significantly. Am I wrong on that thought? Does the 1" bore get that clogged up over the years?

Any other thoughts on what test to do next to figure this out are very welcome! And TIA folks. I'm thinking maybe block off the lower unit intake ports with some duct tape and fill the intake line with barnacle buster or similar for a couple hours.

https://youtu.be/el6Qu5LRvCw

https://youtu.be/yvhJyiAdWwk

 

[muc]

Maybe take a look at #1

https://forums.iboats.com/forum/eng...uiser-i-o-inboard-engines-outdrives/366271-vp

 

[ConchPirate]

Maybe take a look at #1

https://forums.iboats.com/forum/eng...uiser-i-o-inboard-engines-outdrives/366271-vp

Thank you. In reading the tutorial, pg 12 mentions a Clean out access port on the SX-M outdrive. Any idea where that is located and can I get to it with the boat on the lift (in dingy)?

 

[saf]

If you are looking for the air leak, the back flushing test that you did is unlikely to reveal it (IMHO). The pressure inside the intake line during back flushing is pretty low at the outdrive, whatever little water seep out through potential crack or a small hole might be difficult to spot with water pouring out of the outdrive. I would block the intake holes with tape, connect a short 1" hose to the oil cooler (instead of the intake line) and fill it with some colored liquid while raising it up to create some pressure inside the outdrive intake line. If there is a leak you should see the colored liquid seeping through.
This should detect the leak in the upper unit fitting, however, it will not detect a leak in the lower unit (if it's there). The leak in the lower unit would be the exhaust leak, i.e. it only shows up when the engine is running. If you don't find the air leak in the upper unit you can try connecting your port intake line (the one that has a leak) the STBD engine. If your STBD engine does not overheat while the port engine is not running, then it has to be the leak in the lower unit (exhaust leak).

 

[ConchPirate]

If you are looking for the air leak, the back flushing test that you did is unlikely to reveal it (IMHO).The leak in the lower unit would be the exhaust leak, i.e. it only shows up when the engine is running. If you don't find the air leak in the upper unit you can try connecting your port intake line (the one that has a leak) the STBD engine. If your STBD engine does not overheat while the port engine is not running, then it has to be the leak in the lower unit (exhaust leak).

It is near impossible to access the oil cooler in this boat they way they tucked it in. There is like 1/2" of clearance between the top of the risers or cowling to deck and no space (6") between engines, which is filled with pumps. It would take quite a bit of equipment removal to get to the rear areas. With that said I like your idea of connecting it to the starboard engine. That I can do and it will at least eliminate the exhaust part in the lower unit pickup tube. If it runs cool it will show no air leaks or restrictions with the absence of exhaust gasses. Barring that I'll have to call in a pro who may have the gauges and or electronic diagnostic equipment. Thanks for the ideas!

 

[muc]

Thank you. In reading the tutorial, pg 12 mentions a Clean out access port on the SX-M outdrive. Any idea where that is located and can I get to it with the boat on the lift (in dingy)?

It is under the cover on the back of the drive, you will need a new gasket.

I was a pro and i pretty much followed that list. no gauges or electronic test equipment. But ----- hint, hint ----- I did have a tub of pieces of clear hose in different sizes.

 

[dypcdiver]

As I read your post, the overheat is at idle, I like the idea of connecting the STBD engine to the raw water supply of the Port engine for a test.
I have just been through this problem myself but I only had one engine to play with. Exhaust gasses were being forced into the raw water supply by a hole burnt into the tube that connects the water supply between the upper and lower gear-cases.
See here https://forums.iboats.com/forum/eng...-5-0gi-overheats-at-idle-but-fine-at-2000-rpm

 

[ConchPirate]

It is under the cover on the back of the drive, you will need a new gasket.

I was a pro and i pretty much followed that list. no gauges or electronic test equipment. But ----- hint, hint ----- I did have a tub of pieces of clear hose in different sizes.

Yes sir. I did testing with clear hoses and determined it must be supply side based on the testing with a long clear hose connected to the STBD intake line which produced perfectly normal no overheating results. With a short clear attached to the normal port intake line, I didn't really see a lot of air either, so it may be the exhaust gas issue which I will test next by testing the starboard engine on the port side supply. That should eliminate that possibility if the it gets hot as there wouldn't be any exhaust gasses going into the port supply.

 

[ConchPirate]

As I read your post, the overheat is at idle, I like the idea of connecting the STBD engine to the raw water supply of the Port engine for a test.
I have just been through this problem myself but I only had one engine to play with. Exhaust gasses were being forced into the raw water supply by a hole burnt into the tube that connects the water supply between the upper and lower gear-cases.
See here https://forums.iboats.com/forum/eng...-5-0gi-overheats-at-idle-but-fine-at-2000-rpm

WOW. That sounds just like what may be going on. The original owner used the boat in saltwater but kept the boat on a lift and flushed it regularly. But of the other two PO's we are aware of, one of them kept it in the saltwater as evidenced by them having it bottom painted and some barnacle growth found in the outside gimbal/transom plate area where there was no antifoul paint applied. So, it may be that it has some marine growth in that lower to upper chamber area and/or that intake tube is corroded out and it is getting the high temp gasses in as per your links discussion. As was your case, if I rev it up to 2K+ it quickly returns to "normal" temps. Like you I've replaced the pump with a brand new assembly, replaced the thermostat housing and thermostat and checked/tightened clamps on hoses. Unfortunately, the boat lives on a lift and I have no trailer so I will have to farm the outdrive removal work & repair out to a marina that can perform a haulout.

Your link was enlightening. Thank you!

 

[ConchPirate]

The leak in the lower unit would be the exhaust leak, i.e. it only shows up when the engine is running. If you don't find the air leak in the upper unit you can try connecting your port intake line (the one that has a leak) the STBD engine. If your STBD engine does not overheat while the port engine is not running, then it has to be the leak in the lower unit (exhaust leak).

So I did the recommended connectivity by connecting the port engine intake water supply line and connecting it to the stbd engine pump intake. At 3.5 minutes the manifold and riser temps were only 110-114 or so degrees. At 10.5 minutes they were only up to 120F while the thermostat housing was at 155-160. Left it go to 15 minutes at idle and manifolds never exceeded 120F. And the stream of water running through the line was clear and no apparent air bubbles.

This was the same results I got when I had connected the port engine temps by using the stbd engine supply line. After reconnecting the port engine to it's own intake water line, it was hitting 150F on the manifold in under 3 minutes of idle time and the thermostat was still at 120. I also noticed the clear tube I had used for testing for air on the port engine on its own line seemed to have some black greasy (oily) residue on the inside (pics). As I do not see any of the same residue on the longer clear hose pieces that were used when supply was from the stbd side or even the port line feeding the stbd engine without the port engine running, then I suspect this has narrowed the problem down to being an exhaust gas leak into the lower unit water intake line. Guess I'll need to find someone that can yank it out of the water and check it out.

Appreciate the ideas/feedback so far. I'll update when I know more, but marinas seem to be too busy to take on work right now.

PS - I have videos, if anyone is interested I'll post a link.

 

[ConchPirate]

As I read your post, the overheat is at idle, I like the idea of connecting the STBD engine to the raw water supply of the Port engine for a test.
I have just been through this problem myself but I only had one engine to play with. Exhaust gasses were being forced into the raw water supply by a hole burnt into the tube that connects the water supply between the upper and lower gear-cases.
See here https://forums.iboats.com/forum/eng...-5-0gi-overheats-at-idle-but-fine-at-2000-rpm

Well - the verdict is in on the pipe and the news is not good! Marina mechanic pulled the lower unit and found that the pipe on mine is Stainless and in great shape. So the pipe is out. I have asked that they replace the retainer and seal that the tube plugs in to. With the pipe attached to the upper housing they applied some low pressure air with the line capped off at the pump, testing every fitting/hose/oil cooler and the air held for over 24 hours without any drop in pressure at all. So there is no way it can be sucking air that wouldn't show up with the air pressure testing. Also found a bit of water in the lower unit so going to be replacing all seals/gaskets in the lower unit along with the water pipe fittings and seal. If it isn't there and they don't find anything on the back flush it will put us at a loss of ideas.

In other news - the strbd lower unit has a crack in the housing from the rear of the area where the prop attaches and goes forward about 3/4". So new LU case time as well. Sheesh. Thank goodness we live in FL and it isn't like our boating season is about to end as well!!!!!

 

[dypcdiver]

Any updates on this, I'm intrigued.

 

[ConchPirate]

OK - final update! Technician replaced the plastic bushing where the intake pipe inserts into the lower unit. While that was all apart the found and cleaned out some barnacles that had formed in the cavity in the lower unit where the water intake ports are. They also found some barnacles in the chamber where the water passes from the intake pipe to the plastic pipe that the hose going to the bell housing connects. After cleaning everything out, replacing the rubber (plastic?) seals top and bottom of the water intake pipe connects the upper and lower units there was still some overheating, but not as bad as before the cleanout and seal replacements. Changed out the pump impeller and all is well again. Was told that even tho the pump was brand new with under 5 hours of time, that the impellers often take a "set" while sitting on the shelf and even tho they look great, the "set" prevents them from operating at full potential. So all is better now with the port outdrive. BTW - they had found some water in the oil initially so they replaced all seals/gaskets, transom bearing/seal, and replaced a spun hub on that prop.

They also found the starboard drive lower unit was splitting at the prop area so replaced the entire lower unit case, and of course seals, gaskets, as well as the transom plate bearing and seal. Both drives running well and sounding great. This saga is finally over! Yea!

 

[ConchPirate]

Any updates on this, I'm intrigued.

Yes.

 

[dypcdiver]

Thanks for the update, I'm glad it is all fixed, but I do feel sorry for your wallet.

 

[ConchPirate]

Thanks for the update, I'm glad it is all fixed, but I do feel sorry for your wallet.

What wallet? It, my shirt, my sandals, fishing poles and the car all had to be tossed in! No money left for fuel! Ha ha....

 

[Lou C]

Interesting and not that uncommon on salt water boats. On my OMC Cobra there was a plastic water screen in the lower unit just like on the Johnson & Evinrude outboards. Because my boat is moored in salt water approx 5-6 months each season even with painting it with anti fouling paint I still had barnacles growing on this screen. It got to the point where I had mild overheating due to decreased raw water flow. I had to split the lower and upper gear housings to get all the barnacles our and decided to leave that screen out so I could clean out the water intake area with a stiff wire with the boat on the mooring. That was about 7 years ago and I’ve not had overheating problems since. I rod that area out each season at the beginning and then part way through. We don’t have eel grass or seaweed here so I did not really need the screen anyway.

 

[ConchPirate]

One of the PO's had the boat sitting in the water all the time. The original owner kept it on a lift per some pics of it as we do now. Not sure if it was the 2nd, 3rd or both owner(s) that kept it in the water. Hopefully things stay clear now. It's winterized now (beer in the fridge) and ready for some SW Fl fun in the sun. Cheers ----