OMC 4.3L Overheating. Read all the other threads already....

[jpwdesigns]

Re: OMC 4.3L Overheating. Read all the other threads already....

Water is coming out of all the correct places when you are on the muffs because the hose is pushing the water in.
The reason you can take the muffs off while in the bucket is now the engine water pump is doing the work. After a 10 min soak it loses its prime.

Update on this one HCMQA, just tested the pressure by pulling the intake hose off the thermostat housing and starting the engine. Last time i tried this i was in the lake but the impeller wasn't primed so nothing came out. This time i tried it with the muffs on and i got 2 inches of water shooting out so I'm sure my impeller is working and that it is not just suction from the engine water pump.

That's good right?

 

[Lou C]

Re: OMC 4.3L Overheating. Read all the other threads already....

In the vid, the water is coming out the right place, the water comes out mostly at the transom mount and will only come out the prop at high speeds...
You do know your prop is not on right, correct?
In the manual, it says 2"-4" of water is OK.
Another thing you can check is when running the engine on muffs, if you remove the cover ovethe impeller housing, there should be no water leaks around the housing. That hose is to let the pump prime and to let it drain when the engine is off and winterized.
If you still have heating problems, you could have an air leak in the rubber seals, that seal the tube that transfers water from the water intakes up to the impeller housing, this would happen on plane when the upper unit is raised up out of the water. You can splice in a piece of clear hose in the raw water intake hose and check for air bubbles running the engine on plane.....
BTW, these engines with a 160 stat, should run from 160-175 or so, not over 180 unless you are just coming off plane, then it will spike up a bit but after idling a few minutes it should come back to 160-170...

 

[jpwdesigns]

Re: OMC 4.3L Overheating. Read all the other threads already....

In the vid, the water is coming out the right place, the water comes out mostly at the transom mount and will only come out the prop at high speeds....

Thanks!

You do know your prop is not on right, correct?

Oh dear, no I didn't know that. I'm a first time boat owner. I'm fairly handy with a wrench always worked on my own cars/Motorcycles but new to this so what is wrong about the prop?

In the manual, it says 2"-4" of water is OK.

Yup ok there

Another thing you can check is when running the engine on muffs, if you remove the cover ovethe impeller housing, there should be no water leaks around the housing.

Done this, no leaks

If you still have heating problems, you could have an air leak in the rubber seals, that seal the tube that transfers water from the water intakes up to the impeller housing, this would happen on plane when the upper unit is raised up out of the water. You can splice in a piece of clear hose in the raw water intake hose and check for air bubbles running the engine on plane.....

I think this is the most logical answer to my problems. The leak if exists could be enough to cause the impeller to not be able to pull up water....at least that is what i'm thinking. What i find interesting is that when I start the engine with out muffs and it is not pulling up water from intakes, If i pull the little drainage hose off of the impeller housing i get exhaust air blowing up from where the little hose inserts. Can anyone tell me if this is normal? Seems to me like it should be sealed off from the exhaust under normal conditions. SO what I think is happening, is that the exhaust is blowing up that little hose making it impossible for the impeller to get suction to pull up water. IF this is the case, what kind of seals are in the lower unit, or between the upper/lower that would be causing this exhaust seeping into the impeller drainage tube?

BTW, these engines with a 160 stat, should run from 160-175 or so, not over 180 unless you are just coming off plane, then it will spike up a bit but after idling a few minutes it should come back to 160-170...

Yeah i could have some additional restriction from corrosion in the exhaust manifolds slowing down flow or something...but won't bother with that until i can get suction from intakes up to impeller sans muffs.

Thanks again for your thoughts Lou C. Much appreciated!

 

[daman4469]

Re: OMC 4.3L Overheating. Read all the other threads already....

Yeah I guess I hadnt read all the other posts; not sure if the thermostat would help with such an issue, but i doubt it. Others in here probably know a lot more than me!

 

[Lou C]

Re: OMC 4.3L Overheating. Read all the other threads already....

about the prop, the thrust washer (the piece that slides on the propshaft before you put on the prop) is supposed have the inner taper part of it slide up against the tapered part of the prop shaft that matches it. The prop it self will normally fit nearly flush to the lower unit housing, not touching but close.

about the exhaust air coming out the little hose, it's hard to say over the net but you might have a leak in one of the seals on the water tube, in the lower unit look at this pic from doug russell.com, to fix, you need a mechanic, if you are a beginner I would not start by splitting an outdrive. But first maybe fab up a clear hose, to go on the end of the hose that feeds the raw water inlet on the thermo housing. Then run it in the water, both at idle and on plane and see if you have air bubbles in the cooling water. If so, air is being drawn in before the impeller and on a Cobra, the only place that can happen is in the water transfer tube, or the gasket for part 52 on the upper unit, which is where the water transfer tube connects to the upper gear housing...

http://www.dougrussell.com/partscat...6,155,275,157,278,159,161,162,163,164,165,166

parts # 75, 76, also look for obstructions in part 5 the water intake screen, here in salt water land we get barnacles in there....the exhaust passage is the open area in the lower unit right behind where the water tube is mounted...


http://www.dougrussell.com/partscat...6,155,275,157,278,159,161,162,163,164,165,166

now this is the upper gear housing, that water tube fits into part #52, and from there the water goes into the impeller housing, there is also a seal on the upper end...so you may need 2 part #75s, the water seal...

 

[sea wolf]

Re: OMC 4.3L Overheating. Read all the other threads already....

Update on this one HCMQA, just tested the pressure by pulling the intake hose off the thermostat housing and starting the engine. Last time i tried this i was in the lake but the impeller wasn't primed so nothing came out. This time i tried it with the muffs on and i got 2 inches of water shooting out so I'm sure my impeller is working and that it is not just suction from the engine water pump.

That's good right?

Yep, that's good. As a side note, you will not get suction thru the intakes with the drive sitting in a bucket full of water. The impeller housing must be submerged. I'd launch your boat, & let it run for a few minutes at the dock & see what happens. Good luck.

 

[jpwdesigns]

Re: OMC 4.3L Overheating. Read all the other threads already....

Yep, that's good. As a side note, you will not get suction thru the intakes with the drive sitting in a bucket full of water. The impeller housing must be submerged. I'd launch your boat, & let it run for a few minutes at the dock & see what happens. Good luck.

Thanks. Yeah i did try that and had same results. I'm pretty sure I know what the issue is. Starting to find other threads with the same issue. http://forums.iboats.com/showthread.php?t=385454&page=2&p=2730038&viewfull=1#post2730038

 

[jpwdesigns]

Re: OMC 4.3L Overheating. Read all the other threads already....

I'm really not happy about it but I think you're right. I found this http://forums.iboats.com/showthread.php?t=385454&page=2&p=2730038&viewfull=1#post2730038 which looks exactly like my issue and this http://www.boatered.com/forum/topic.asp?TOPIC_ID=84932 which sound exactly like what you're describing.

Going to auto parts store today to get the clear hose. Can you confirm that it is 3/4" ?

 

[jpwdesigns]

Re: OMC 4.3L Overheating. Read all the other threads already....

Not sure that it matters but I ran the clear hose test to look for bubbles in the intake hose before the thermostat housing and guess what, no bubbles. So I'm not sucking air when on muffs. Going to take it to the lake with a jimmy rigged muff pump to try to prime the impeller manually and see if i keep prime while submerged fully. If so then going to take it for a drive and see what happens. If its all good i'm going to make do with my jimmy rig until next spring. Not enough weekends left this year to tear into the lower unit or take it to a mechanic.

 

[sea wolf]

Re: OMC 4.3L Overheating. Read all the other threads already....

Not sure that it matters but I ran the clear hose test to look for bubbles in the intake hose before the thermostat housing and guess what, no bubbles. So I'm not sucking air when on muffs. Going to take it to the lake with a jimmy rigged muff pump to try to prime the impeller manually and see if i keep prime while submerged fully. If so then going to take it for a drive and see what happens. If its all good i'm going to make do with my jimmy rig until next spring. Not enough weekends left this year to tear into the lower unit or take it to a mechanic.

The test with the clear hose should be done with the boat in the water. When running the engine on muffs the pump will normally suck some air, hence you will see some air bubbles in the hose. But the fact that u didn't see any is a good sign.

 

[HCMQA]

Re: OMC 4.3L Overheating. Read all the other threads already....

Sorry I do not have the link but I did read another thread on here but it was someone with a lot more knowledge than me.

But what the issue maybe is that the impeller pump system is not designed to pull water up. So what that means is that the pump MUST be in water to a level above the pump in order to prime. (As mentioned above) So you do not really need to take it out if you can find a slow ramp you can just back it into the water deep enough while leaving on the trailer with the drive all the way down and run it that way to see if it will prime.

If you do not know that your prop is falling off in that you tube vid than we need to work with you a lot closer to make sure no one gets hurt.

 

[jpwdesigns]

Re: OMC 4.3L Overheating. Read all the other threads already....

If you do not know that your prop is falling off in that you tube vid than we need to work with you a lot closer to make sure no one gets hurt.

:facepalm: Ok humiliation of ignorance is setting in now. What do i need to do to fix it? By the way, that's how it was when i got the boat. I've not touched it, but i don't know enough to tell that its wrong so please point me in the right direction and i'll get it squared away.

 

[Lou C]

Re: OMC 4.3L Overheating. Read all the other threads already....

Either they got the wrong thrust washer on there, put it on backwards or for some reason the thrust washer did not slide up the prop shaft far enough...the washer has a tapered area, that slides onto a taper on the prop shaft... the tapered area goes on the shaft facing the drive, it should slide right up flush.the prop has to be close to flush to the lower unit housing....look at my crude pic, I would have scanned a pic but this shows it better.....

And about the priming, I think the Cobra, because of the location of the water pump being as high as it is, has to be in the water with the drive lowered to prime. That little hose, helps in priming because it allows air out of the housing, as the water flows up the water tube when the drive gets submerged. In fast if that were clogged, it might have an air bubble in the impeller housing.

What I'd do is back it in at the ramp lower the drive and see if it primes. If so, then take off the engine cover, and have someone watch that clear hose. You want to get the boat on plane (if it doesn't overheat right away) because that's when it's more likely to pull in air from the seals in the drive I told you about, they are on the suction side of the system. You will not pull in air on the pressure side usually (after the impeller) it will be on the suction side (before the impeller)......

 

[jpwdesigns]

Re: OMC 4.3L Overheating. Read all the other threads already....

Thanks Lou. I'm going to look into this prop thing to figure out what is going on there. That thrust washer slides in and out about an inch or so. I thought that was weird. Should it be sandwiched with little movement room?

 

[Lou C]

Re: OMC 4.3L Overheating. Read all the other threads already....

It's not the right one or it's not on the right way. The taper in the hole of the washer, will match thtaper on the prop shaft exactly. Slides on and no play, slides up almost all the way to the lower unit housing....

 

[jpwdesigns]

Re: OMC 4.3L Overheating. Read all the other threads already....

How does this look

I think the other propeller was the wrong size for this boat. I know the nut is kinda sticking out but its extra long. Longer than the ones in the pic in my manual. cotter pin goes through a hole in it rather than through a notch in the end.

 

[HT32BSX115]

Re: OMC 4.3L Overheating. Read all the other threads already....

Check those risers....and take that thermostat out! Mine gave me problems for years, even when I would replace it, and I removed it a few years ago. Runs nice and cool ever since, with no cooling issues. Some may disagree, but I chased that issue around for a long, long time and thermostat removal solved it.

Howdy,


I didn't see anyone mention anything about this......DO NOT RUN without T-stat.

I'll cause more problems than you think you fix.....

 

[jpwdesigns]

Re: OMC 4.3L Overheating. Read all the other threads already....

Howdy,


I didn't see anyone mention anything about this......DO NOT RUN without T-stat.

I'll cause more problems than you think you fix.....

roger that

 

[Gettinther]

Re: OMC 4.3L Overheating. Read all the other threads already....

Check those risers....and take that thermostat out! Mine gave me problems for years, even when I would replace it, and I removed it a few years ago. Runs nice and cool ever since, with no cooling issues. Some may disagree, but I chased that issue around for a long, long time and thermostat removal solved it.

daman4469 It may run cool but you didn't fix anything you just masked the real problem and solved nothing , and are likely causing some other problems running it too cold, but as long as you are happy it is after all your boat.

jpwdesigns you deserve a lot of credit for stickin to it and trying to repair your problem or problems, Don't give up you will get it . You have access to a lot of great help in this forum.

 

[jpwdesigns]

Re: OMC 4.3L Overheating. Read all the other threads already....

jpwdesigns you deserve a lot of credit for stickin to it and trying to repair your problem or problems, Don't give up you will get it . You have access to a lot of great help in this forum.

Thanks Gettinther! Taking it to the dock after work today with my son to see if we're going to have any fun on Saturday!