Overheated 1989 4.3 OMC questions...

[maine4winns]

First off - I have had this boat for going on 2 seasons and have only had it in fresh water with maybe 30 hours last year and ZERO this year!

I winterized according to original manual and post found here. There are no issues with water leaking into the bildge from cracked block or freeze plugs or hoses. I did NOT replace or inspect the water pump impeller and housing until after the overheating issue.

I started the engine on the water hose driveway muffs and ran it for maybe 1 minute tops for winterizing and 1 minute for the spring commissioning.

Launched the boat last week and started it up at the landing dock. As always - I let it warm up to operating temp. all other gauges read within spec as well.

Put it in reverse, then forward and cruised at about 5 MPH with the engine cover open so that I could occasionally check the motor. Increased speed to 10 MPH and engine temp jumped up to 200deg F fairly quickly. *This has been a fresh water boat only and I am the second owner. Brought the brough down to idle and headed back to dock. I noticed smoke coming from the outdrive area and I assume it was from the heat on the hoses??

Checked bilge and NO water in bilge. Brought boat back home. Removed the Water Pump assembly (See Pictures). The impeller does not (in my opinion) look like it would be the cause of overheating - but perhaps it was allowing air to come through with the water? The Water Pump Liner did show burt rubber (perhaps from previous impeller?).

I purchased a new thermostat, and a COMPLETE water pump kit and new housing as well. I will install them today or tomorrow. I will also check the inlet side of the power steering cooler for debri. The other thing I will check in corrosion / clogging at the thermostat housing itself. I do have the original bat wing exhaust system, but during winterization I am not getting a lot of rust / corrosion / material when draining and I get a good flow of water at pet cocks. ​

​

There is no sign of water in the oil (emulsion), yay on that note! Compression test is great on ALL 6 cylinders as well.​

​

**My question: I assume the smoke was from the rubber hoses (exhaust?) getting hot. Should I inspect / replace them? Are there other hoses I should check? I will check the two bellows as well.​

​

I have NOT had the drive off of the engine and I realize that I probably should remove and inspect a whole lot of sh*t! The shift cable is slightly off so that is going to be a learning experience.​

​

Not being a firm believer in running the engine muffs in the driveway (water pressure is just too low), I will test the motor in the lake at the dock next week after I do the above maint.​

​

I have found a lot of info on these and similiar engines overheating and I think I am covering all bases - but please chime in!

Thanks!

 

[maine4winns]

When comparing the new impeller with the old impeller (see pics) I noticed (besides the worn vanes) that the Drive Pocket was partially gone! I will be inspecting the inlet to the Power Steering cooler and flushing it out.

First off - I have had this boat for going on 2 seasons and have only had it in fresh water with maybe 30 hours last year and ZERO this year!

I winterized according to original manual and post found here. There are no issues with water leaking into the bildge from cracked block or freeze plugs or hoses. I did NOT replace or inspect the water pump impeller and housing until after the overheating issue.

I started the engine on the water hose driveway muffs and ran it for maybe 1 minute tops for winterizing and 1 minute for the spring commissioning.

Launched the boat last week and started it up at the landing dock. As always - I let it warm up to operating temp. all other gauges read within spec as well.

Put it in reverse, then forward and cruised at about 5 MPH with the engine cover open so that I could occasionally check the motor. Increased speed to 10 MPH and engine temp jumped up to 200deg F fairly quickly. *This has been a fresh water boat only and I am the second owner. Brought the brough down to idle and headed back to dock. I noticed smoke coming from the outdrive area and I assume it was from the heat on the hoses??

Checked bilge and NO water in bilge. Brought boat back home. Removed the Water Pump assembly (See Pictures). The impeller does not (in my opinion) look like it would be the cause of overheating - but perhaps it was allowing air to come through with the water? The Water Pump Liner did show burt rubber (perhaps from previous impeller?).

I purchased a new thermostat, and a COMPLETE water pump kit and new housing as well. I will install them today or tomorrow. I will also check the inlet side of the power steering cooler for debri. The other thing I will check in corrosion / clogging at the thermostat housing itself. I do have the original bat wing exhaust system, but during winterization I am not getting a lot of rust / corrosion / material when draining and I get a good flow of water at pet cocks. ​

​

There is no sign of water in the oil (emulsion), yay on that note! Compression test is great on ALL 6 cylinders as well.​

​

**My question: I assume the smoke was from the rubber hoses (exhaust?) getting hot. Should I inspect / replace them? Are there other hoses I should check? I will check the two bellows as well.​

​

I have NOT had the drive off of the engine and I realize that I probably should remove and inspect a whole lot of sh*t! The shift cable is slightly off so that is going to be a learning experience.​

​

Not being a firm believer in running the engine muffs in the driveway (water pressure is just too low), I will test the motor in the lake at the dock next week after I do the above maint.​

​

I have found a lot of info on these and similiar engines overheating and I think I am covering all bases - but please chime in!

Thanks!

First off - I have had this boat for going on 2 seasons and have only had it in fresh water with maybe 30 hours last year and ZERO this year!

I winterized according to original manual and post found here. There are no issues with water leaking into the bildge from cracked block or freeze plugs or hoses. I did NOT replace or inspect the water pump impeller and housing until after the overheating issue.

I started the engine on the water hose driveway muffs and ran it for maybe 1 minute tops for winterizing and 1 minute for the spring commissioning.

Launched the boat last week and started it up at the landing dock. As always - I let it warm up to operating temp. all other gauges read within spec as well.

Put it in reverse, then forward and cruised at about 5 MPH with the engine cover open so that I could occasionally check the motor. Increased speed to 10 MPH and engine temp jumped up to 200deg F fairly quickly. *This has been a fresh water boat only and I am the second owner. Brought the brough down to idle and headed back to dock. I noticed smoke coming from the outdrive area and I assume it was from the heat on the hoses??

Checked bilge and NO water in bilge. Brought boat back home. Removed the Water Pump assembly (See Pictures). The impeller does not (in my opinion) look like it would be the cause of overheating - but perhaps it was allowing air to come through with the water? The Water Pump Liner did show burt rubber (perhaps from previous impeller?).

I purchased a new thermostat, and a COMPLETE water pump kit and new housing as well. I will install them today or tomorrow. I will also check the inlet side of the power steering cooler for debri. The other thing I will check in corrosion / clogging at the thermostat housing itself. I do have the original bat wing exhaust system, but during winterization I am not getting a lot of rust / corrosion / material when draining and I get a good flow of water at pet cocks. ​

​

There is no sign of water in the oil (emulsion), yay on that note! Compression test is great on ALL 6 cylinders as well.​

​

**My question: I assume the smoke was from the rubber hoses (exhaust?) getting hot. Should I inspect / replace them? Are there other hoses I should check? I will check the two bellows as well.​

​

I have NOT had the drive off of the engine and I realize that I probably should remove and inspect a whole lot of sh*t! The shift cable is slightly off so that is going to be a learning experience.​

​

Not being a firm believer in running the engine muffs in the driveway (water pressure is just too low), I will test the motor in the lake at the dock next week after I do the above maint.​

​

I have found a lot of info on these and similiar engines overheating and I think I am covering all bases - but pl

 

[maine4winns]

The Power Steering oil cooler is clear of any obstructions. I do question if this heat exchanger is defective (see attached picture) .
I need to flush the raw water inlet hose to outdrive (the one I disconnected at inlet to cooler).
I am just not sure if I need to remove anything besides the water pump assembly on the drive. *like do I need to remove the lower unit?

I noticed that the port on the left side of the water pump discharge (on outdrive itself) was full of water. The right side is clear. I am not sure if this is normal with the drive fully raised. Perhaps this is a sign of a clog somewhere upstream?? See attached pictures.

The Thermostat looks original to the 1989 manufacturing date! I know that is highly unlikely - but it is bad. More likely than not this was stuck closed and was the culprit, but I will not know until I get everything flushed and put back together.

This brings me to my final question that I am probably going to answer myself! The corrosion in the thermostat housing is pretty bad - but this is my first exposure to working on a marine cooling system, so I am not sure if it warrants replacement. If it does - I should probably change out the original bat wings with the conversion kit.

"Buy a boat...." my wife said! LOL

 

[Renken2000Classic]

My thermostat housing looks bad (rusty), where the hoses connect. I've chalked it up to just how it is with a boat. Haven't had it off. Freshwater boat.

I had an overheat in 2019 with the batwings, left side. We were on plane and I smelled something burning (rubber coupler in the exhaust system, prob), and the water temp was up some. I stopped and pulled the cover, and it was crackling in there. Spooked me enough that I discharged the extinguisher briefly (not necessary, prob).

Took it back to the dock under less power and replaced those with a complete GLM system. Runs cooler with that than the original manifolds, and they were considerably corroded inside. Not necessarily suggesting GLM, but it's worked for me so far.

 

[Lou C]

You can see that the outlets on these are pretty small, I had them on my 4.3 as well, after 5.5 seasons in salt water they looked like the one on the right. I had 3 sets of these on my '88 4.3 here in the salt you have to change them every 5-7 years, or else, you have overheats, or a hydrolock if they rust though. I replaced them with the later style exhaust using Barr Marine manifolds and elbows and the V/P aluminum downpipes and rubber hoses.

the first thing you should do with any new to you boat is change the raw water impeller, that is a maintenance item usually every 3 seasons, they do wear out and take a set, and won't pump water that well. The one in your pix is no good it probably was at least partially responsible for the overheat. The other possible culprits are the stat and clogged manifold outlets.
the rust you see there in the thermo housing is typical, you can clean it up with wire brush, and ream out the water passage hoses with a coat hanger.
the manifolds, I'd take em off and check to see how the water outlets look. Those can be reamed out too if the clogging isn't too bad.
You're in freshwater? If so that's not so risky, here we just have to replace them. I replaced the thermostat housing and manifolds 3 times, in 20 years in the salt. The problem with the one piece design used by both Merc and OMC was that they had trouble getting consistent wall thickness, some were fine and some were very thin in certain areas and that could cause a hydrolock. I never had a problem with mine other than having to replace due to salt water use. I do like having the 2 piece system because I can remove the elbows to inspect, might only have to replace them after next season, I will see when I check the manifolds by filling with acetone.
You can see how much larger the water passages are on the 2 piece units.

 

[maine4winns]

Thank you Renken and Lou! I don't know what to expect when trying to remove the Exhaust Manifolds for inspection. I have done my fair share of Car Exhaust Manifolds and they were a nightmare - almost always broke a stud when removing. Has this been your experience as well? Or perhaps they are not exposed to as much direct heat with water flowing through them?

At anyrate I have put an entire new water pump assembly on (followed the OMC manual), I cleaned the thermostat housing best I could, put a new thermostat, o ring and housing gasket on. I will NOT be testing this on the hard - but rather at the boat launch / lake.

Have a great day all and keep you posted. I will be removing the batwings if it still overheats - but if it runs fine temp wise, I will wait until fall or early spring and get as much out of these as possible.

The new 2 piece design is NOT cheap. I will research other posts on this subject as I am not sure if the kit is complete or if I need additional hosing ect....

 

[Lou C]

IIRC I paid back in 2017:
Barr Kit $725
Each of those VP down pipes was like $210, the hoses & clamps maybe another $100 (these were all brand new), so it was like $1250 for all the parts. If you’re in fresh water you’ll do this once; here in the salt pond we have to change manifolds & elbows every 5-7 years or else risk overheats & hydro locks. This boat since I’ve owned it (21 years) is on its 4th exhaust system. When you could still get the batwings new they were $820 a pair. So if you do this once well you’re getting away cheap!
My exhaust costs over 21 years:
2 sets of replacement batwings = $1640
2 piece conversion $1250
That’s $2890, yep almost 3 grand to keep my engine alive in salt water for 20 seasons. Fresh water guys, don’t complain!

 

[maine4winns]

Lou - your information is invaluable and gives me hope as to the longevity of a new exhaust system on my fresh water boat!

Was wodering how difficult it was to remove the nuts from the exhaust manifold studs?

Forgive my ignorance / lack of knowlege - but what is the VP Down Pipes? Do they connect to the new riser hoses?

Thank you

 

[Lou C]

Very easy to remove those nuts. To pull the manifolds you have to spray silicone spray on the Y pipe & slide the bottom hoses down over the Y pipe. Might have to shove a thin screwdriver under the rubber & heat it a bit with a heat gun to get ‘em loose they kinda get baked on….
The down pipe is the 90* pipe between the upper hoses that go on the elbows and the lower hoses that go on the Y pipe.
When you take off your batwings post up a pic of the outlets you might get lucky they might not be rusted & clogged & might not need to be replaced yet. Even if slightly clogged you can rod them out with a coat hanger & test the flow by hooking up a garden hose to it. I used to test mine by filling with Acetone (off the engine) & let it sit to check for leaks. Mine never leaked but the longest I used them was like 6 seasons.

 

[Lou C]

 

[Lou C]

Down pipe is part # 19 above. You can see all the components of the 2 piece system in this diagram. OMC & Volvo used this basically identical system.
Some parts you won’t need with a pre Vortec V6 (pre 1996) are the one way check valves (part # 5) that are screwed into the exhaust elbows; these are only needed for Vortec engines.

 

[maine4winns]

Lou, again thank you!

 

[Renken2000Classic]

Yeah I don't remember having any trouble with the fasteners, getting the old stuff off. And I used some anti-sieze on the new bolts. One thing that threw me was the left and right new style manifolds are the same part. But that's just how the 4.3L V6 is.

Easy assembly, and a lot easier than leaning over under a land vehicle hood to do it!

One thing I'll add about the GLM manifolds - they looked almost as if they weren't melted hot enough (?; surface looked like styrofoam, with little pellets visible), and one of them had a pinhole leak near the bottom. The company made it right and sent me a replacement, but it sealed itself up before too long with rust or whatever, and I never changed it out.

I don't believe part #21 above (rubber coupler) came with my kit, and I had to order them separately.

 

[Lou C]

The Barr manifolds I used were very well cast & sealing surfaces perfect. They do need a better coat of paint to not rust in damp salt water environments; I brushed on a coat of Rustolium….

 

[maine4winns]

1. New water pump (complete) installed... (OEM)
2. New thermostat installed... (OEM)
3. Removed Power Steering oil cooler - no impeller pieces, yay
4. Flushed out hoses from the stern to the thermostat housing (housing removed) and vice versa - no cloggs.
5. Removed port and starboard batwings... There was some corrosing that I scraped and flushed out but I could not see any restrictions. The engine block water passages were clear as well. *This boat has only seen fresh water, thankfully. Put new gaskets and Batwings back on block.
6. Checked the Exhaust Flappers (check valves) in the port and stbd exhause pipes - yup, the pins were about done and the flappers were toast as well but both intact. Installed new Flappers, Bushings and Pins for both sides.
7. Now I moved on to the two bellows on the outdrive. The exhaust bellows is a little dry rotted - but will definetly make it through the season. At first, when I saw the holes in the bottom of the exhaust bellows, I was like oh sh&t. But they are too uniform to have been created by the overheating issue. The drive bellows look new.

Nonetheless (unless I have to sooner) I will be venturing inton removing this outdrive at the end of this season. We only go out 1-2 days a week.

What specialty tools will I asolutely need to purchase?

Thanks all,

Greg


I have NEVER had this drive off and as I said - my plan was to remove it this fall and have a winter project in my garage.

 

[Lou C]

The slits on the exhaust bellows are normal, to reduce back pressure.
As long as your 4 exhaust ports are open on the batwings, you should be OK. They are small so they clog easily. Good thing you changed the flappers.
You should be pulling the drive at the end of each season. I built a wood stand for mine but later bought an outdrive jack which makes the R&R much easier. No special tools needed but a long thin screwdriver to turn the driveshaft when you reinstall the drive makes it easier and you should get an alignment tool to check alignment each season. This is what I've done here in the salt pond and it has helped make the Cobra last a LONG time.
The drive looks the way it does due to being painted with anti fouling every season for 21 years. But works just like new.

 

[maine4winns]

I love that ift / transport cart you bought! I have searched them and they are a pretty penny. I'm thinking about building one without a lift on it, but at least a stand with a rolling platform under it.

Thanks Lou!

 

[Lou C]

I bought it about 10 years ago. I think I paid about $175. Stumpy’s Fab Works. If you’re going to own I/O boats a long time it’s worth it.

 

[maine4winns]

$284 plus shipping now. But still available! Depending on shipping costs - I will probably order one!

Thanks

 

[Lou C]

I figure it saved me about $3,000 in maintenance over 10 years. My boat has not been back to a mechanic since 2006. Ive done all of it including winterizing tune ups, carb rebuilds, drive r & r & shift linkage adjustment. Also did a top engine overhaul (installed reman cyl heads) & the exhaust conversion about 6 years ago.