Logo
FULL SITE MENU

Mercruiser 5.0 Water Leak at Flywheel

T

Tahoe_User

New member
New to this forum so may not know all the etiquette so bear with me.

I have a Tahoe Q6. Mercruiser 5.0 liter with stern drive. Last season it ran pretty good but would always stall on my return trips and I would have to limp home. I am running on the ocean off Mass. So I had a guy look at it and we found water in the oil. he did not think block was cracked so he redid intake and exhaust manifolds and found cracks in there. Ran it in driveway...ran like a top...super psyched...by far best it ever ran. My boat dominates when its sitting in the driveway...best driveway boat ever.

took it on the ocean in May 2023. it ran like a beast. It was awesome...when boat's behave the experience is really hard to match. Anyway, as soon as my head created those thoughts the boat stopped behaving. The engine compartment filled up with what I thought was smoke but in retrospect It was like super super hot steam. Did not smell like smoke. It was very white. It sort of sounded like a camp fire as it made a lot of popping/cracking noises. bilge was completely filled with very cold ocean water...super filled. water was up to starter. I actually thought I forgot to put my drain plug on so did some very uncomfortable swimming and it was there no problem.

Shut down engine....let everything settle and unfortunately just drifted for like 20 mins. Started back up, no problem. Drove back to port and then "smoke" started again so shut it down and rowed in. Rowing a 3,000 pound boat is not as fun as it sounds. If there was a breeze I would have been screwed. Got boat on land and it would not start. Finally had time this weekend to get in there and this is what I found:

- Starter is dead....super dead. took it out, tried to jump and nothing doing. So ordered a new one.
- Bilge pump was not working. It had some kind of plastic wrapper (like from a candy bar or whatever) and other crud. the floating switch was not healthy either so unjammed that and now it works great.
- Big mega Problem, maybe two....there is a water leak at the fly wheel...so I am not starting engine but I am putting garden water hose in to hose at front of engine and water is coming out at the fly wheel. I am told there are (2) core plugs or freeze plugs???? up behind the fly wheel and only way to access them is to remove stern drive and then pull motor...yay!....any thoughts on this?
- To see the water leak I removed the oil filter. The oil was grey...not good. So either water was leftover in there from last season or water is still getting into the engine from a cracked block.

i will put in new starter and run it in driveway. Likely it will work fine like this. I will then take to local lake and test it there so I am not dealing with ocean conditions. I suspect it will run fine but if I have block crack then when engine heats up the crack will expand and things will go badly. I have a pal on that lake so we may just run it at his dock so I am not suck in middle of lake rowing home again.

any thoughts are greatly appreciated. I suspect I will be pulling engine in the off season.
 
You have likely removed all the babbitt material off the main and camshaft bearings by operating it with water in the oil and by overheating it a couple times. You'll probably have to confront Big Bill. The engine can pass compression and leak down tests but still be completely farked. The thing got you home more or less, and that's gonna be it's last voyage I believe.
 
Bt Doctur said:
redid intake and exhaust manifolds and found cracks in there.
exactly how was it winterized
Click to expand...
winterization had an issue....it was done well but plastic cover got torn through by falling branch and I was not aware of the big big hole in the cover...I keep it off premise...so it got land swamped. Even with plug pulled there were some heavy rains that filled the boat up with water...like I can see the water line inside the cabin of boat
 
Tahoe_User said:
winterization had an issue....it was done well but plastic cover got torn through by falling branch and I was not aware of the big big hole in the cover...I keep it off premise...so it got land swamped. Even with plug pulled there were some heavy rains that filled the boat up with water...like I can see the water line inside the cabin of boat
Click to expand...
Ayuh,..... It's my guess the winterization went worse than you think,.....
If you found freeze busted manifolds, I'm pretty sure the motor froze as well, hence the core plugs behind the flywheel leaking, 'n water in the oil again,......

Quickest, 'n easiest way to get back on the water is with atleast a new / reman long block crate motor,.....
 
o2batsea said:
You have likely removed all the babbitt material off the main and camshaft bearings by operating it with water in the oil and by overheating it a couple times. You'll probably have to confront Big Bill. The engine can pass compression and leak down tests but still be completely farked. The thing got you home more or less, and that's gonna be it's last voyage I believe.
Click to expand...
this is great feedback. This makes sense to me. Is there any way of doing a test that confirms that the block is cracked? so now the big question is...do I even bother with this anymore? I assume replacing the block means pulling the engine and the work is substantial. I did not pay much for the boat and got three seasons out of it on the ocean. I don't want to do I/O again for ocean boating. It is a real pain to get in that engine cabin to do really anything. I am guessing to fix this I am looking at $8000-$10,000...or do it myself but big time commitment. Alternatively, I go buy smaller outboard motor Whaler or Rabolo which is a little smaller (which I prefer as I trailer the boat) more ocean worthy and engine is easier to maintain. I am leaning towards just giving up on my Tahoe and buying something more appropriate for ocean use that is smaller with outboard
bondo said:
Ayuh,..... It's my guess the winterization went worse than you think,.....
If you found freeze busted manifolds, I'm pretty sure the motor froze as well, hence the core plugs behind the flywheel leaking, 'n water in the oil again,......

Quickest, 'n easiest way to get back on the water is with atleast a new / reman long block crate motor,.....
Click to expand...
can you let me know what this is "reman long block crate motor"...I think you are saying replace the block
 
Tahoe_User said:
Alternatively, I go buy smaller outboard motor Whaler or Rabolo which is a little smaller (which I prefer as I trailer the boat) more ocean worthy and engine is easier to maintain. I am leaning towards just giving up on my Tahoe and buying something more appropriate for ocean use that is smaller with outboard
Click to expand...
Ayuh,..... This sounds like the direction you oughta go, as, Yes, yer current motor appears to be scrap iron,.....
 
I wouldn't bother testing the engine. Take the money you would spend on repairs and go find another boat that meets your needs better. Maybe you can donate this one to a local charity so they can make a buck or two off it.
 
thanks again for all of the advice here. I have someone who want to buy the boat. They have been advised of the issues and just want to see iit start. So, I charged all 3 batteries, I put in a new starter. Tried ignition and NOTHING. So, first thought was the fuse at the starter. Checked power at the hot line that goes to the starter...NO POWER at that hot line. Can you folks advise next link up the chain that would disrujpt the power. I assume there is another big fuse or circuit breaker or relay somewhere that has **** the bed. Thanks for your help.
 
thank you sir. your feedback has been spot on and I greatly appreicate it your experience and candor. I think you are referring to this circuit breaker in this pic....there is no power getting to this guy. so i looked at the wiring harness, popped that open and sanded the crap out of the pins and still nothing...so I am now tracking back from this CB to battery and it is really fussy because a lot of the wires are behing the engine in mon man's land0.jpg
 
Tahoe_User said:
thank you sir. your feedback has been spot on and I greatly appreicate it your experience and candor. I think you are referring to this circuit breaker in this pic....there is no power getting to this guy. so i looked at the wiring harness, popped that open and sanded the crap out of the pins and still nothing...so I am now tracking back from this CB to battery and it is really fussy because a lot of the wires are behing the engine in mon man's landView attachment 30924
Click to expand...
usually that is fed off the positive lug on the starter but goes through a 90 fuse down there that is a PITA to get to verify 12v at starter lug and down stream of this 90a cube fuse
 
Dieter said:
usually that is fed off the positive lug on the starter but goes through a 90 fuse down there that is a PITA to get to verify 12v at starter lug and down stream of this 90a cube fuse
Click to expand...
Thank you sir. I have no power at the starter lug. any chance you meant to say power is from battery positive lug then to 90amp cube and then to starter motor. So, on my side to clarify...I used to get power right up to the starter but the fuse at the starter was bad. So replaced that and I was in business. Now there is no power at all getting to the starter from that hot line. that hot line is just dead.
 
Tahoe_User said:
Thank you sir. I have no power at the starter lug. any chance you meant to say power is from battery positive lug then to 90amp cube and then to starter motor. So, on my side to clarify...I used to get power right up to the starter but the fuse at the starter was bad. So replaced that and I was in business. Now there is no power at all getting to the starter from that hot line. that hot line is just dead.
Click to expand...
no i meant starter lug 100%

google a wiring digram for mercruiser. Power goes from the battery positive post to the starter. On this starter post the fuse is attached downstream of the battery feed to starter and then feeds the 50 a breaker


thee is no fuse between battery and starter positive lug unless someone took it apart and miswired it. If you are measure no voltage at the starter positive lug then you have a cable issue to battery, loose or corroded battery cable connections. Ground connections are just as important as the positive side
 
Dieter you were correct. The connection at battery was poor. I sanded that and now I have power to the starter. There is a fuse right at the start lug. Looks like a white plastic block. I am trying to post a pic below here. that tested fine. So, now I have power going to the starter and the starter is spinning but it is not engaging the fly wheel. So, I think this is progress but not sure why plunger is not plunging the gear into the fly wheel. I am hoping it simply that I reversed the wiring on the solenoid. going out now to take pic of that wiring and compare to my diagram. All this discovery only cost me 20,000 mosquito bites.

1691542669863.png
 
well...it is wired correctly. small yellow red is clockwise to the positive lug on the starter. So, I will have one of my kids turn key to start while I am down there with multimeter to see if power is coming through the yellow red wire which I believe is what drives the plunger. If power is there then my new relatively cheap starter motor simply does not work. I should have jumped it before i put it in the boat to make sure it worked
 
OEM parts are best.... next best is a premium aftermarket ( Sierra)... beyond that you are shooting craps. In so far as replacement engines... I've reengined two boats in my life. In both cases I did the cost/benefit/risk/boat usage analysis and decided to buy new all up factory crate engines. A few bucks more, but they come with enforceable warranties without finger pointing. Best of all, to my mind at least.... faster more troublefree turnaround and install and back on the water.
 
Sandkicker, I was hoping you were wrong and I could save myself money on these parts but this is second NON OEM starter I put in there in 9 months so I think you are right. I just realized I can run power to the solenoid only to see if the plunger is working. I will give that a whirl today or tomorrow.
 
Wet bilges on engines eat starters ( even if top mounted!)... by wet I mean enough water to get the bottom of the flywheel cover immersed. BTW, On MERC engines I've found, the failure rate of the solenoid is about 2X the starter itself.
 
Tahoe_User said:
Sandkicker, I was hoping you were wrong and I could save myself money on these parts but this is second NON OEM starter I put in there in 9 months so I think you are right. I just realized I can run power to the solenoid only to see if the plunger is working. I will give that a whirl today or tomorrow.
Click to expand...
While you are down there check what the voltage drop is when the starter cranks seeing what yo had when you werent getting any volts not cranking maybe you are loosing enough voltage that it wont kick the gear out.

If low maybe run jumper cable to the lug in parrallel to see if it helps before janking the starter

OEM and DB electric are two quality names that keep coming up
 
I got it running. There were several problems. Problem #1 - the starter was wired correctly, however, when I tightened the nut on the yellow red wire it spun the metal contact at end of wire and this touched the big negative terminal. So motor spun but would not plunge. I redid that and all good. Started right up. Second problem was the bilge pump. I wiped away all the outside debris and it was working fine. on my test last week. When I got boat going tonight, nothing doing...so had to crawl in there and pop out the little impeller motor, cleaned that and more importantly flushed out all the debris in the yellow housing that it sits in. with a hose. Popped impeller motor back in, zip tied floating switch to yellow housing and back in business. Boat run in drivway with muffs for about 30 mins, no overheating, ran great, no issues. Water is still coming out at back of engine but bilge pump is not getting overwhelmed. So, I am not convinced I have a cracked block but not sure either. I will take it to fresh water pond with a dock on Sunday and test and see what happens. Definitely not going out on ocean again proabably until I get the engine pulled and leak resolved. I may also move the bilge pump back to where the leak is right by the fly wheel.
 
Tahoe_User said:
Water is still coming out at back of engine but bilge pump is not getting overwhelmed. So, I am not convinced I have a cracked block but not sure either.
Click to expand...
Ayuh,...... With a leaking motor filling the bilge, relying on a bilge pump to keep you afloat, sure doesn't sound very safe,.....

Be sure everybody is wearing PFDs,.....
 
bondo said:
Ayuh,...... With a leaking motor filling the bilge, relying on a bilge pump to keep you afloat, sure doesn't sound very safe,.....

Be sure everybody is wearing PFDs,.....
Click to expand...
Yeah I was gonna say stay near shore. Willing to bet has a core plug pushed out or rotted through. Might not be the most well thought out plan
 
took boat to local pond that a lot of folks use for waterskiing pontoon boating etc. , dropped it in, started right up. Boat ran great...zipped around for about 10 mins high throttle, low throttle, idle...all very good...on idle it is very quiet so I am skeptical of cracked block but not 100% sure....coolant leaked into bilge but pump was working and at first pump was keeping up but it soon fell short and bilge was really filling up. so we stayed close to dock and just pulled it out. pulled it out and oil tube screw on strern was out...so that was super annoying because not sure if leak coolant leak in eninge overhwelmed pump or the combination of that and the open hole for oil tube did me in.
Couple of questions: What is driving rate of the impeller? Is it always at a set rate or does it go faster and pull in more water as you rev higher RPMS?
I believe running temp of Mercruiser 5.0 is 160F. My temp needle did not budge so now worried that coolant not getting through entire engine to that thermostat that provides data to the temp gauge.
I will likely get faster bilge pump and put it in more towards rear of bilge where water collects initially. will leave the other one in there and just move the drain tube from old one to new one.
 
Ayuh,..... Pull the motor, 'n replace the missing core plug,.......

Yer gonna burn up yer motor, because the water level in the block, can't get any higher than the big hole where the core plug belongs,.....
 
I think coolant is getting up through higher part of block. see attached pic...the red circle is where the plug is that I think it the culprit. If I keep the boat I will pull motor but I think becaue the freeze plug is high in the block that it is getting coolant to the block.....however, I believe the coolant than is suipposed to go to the riser and manifold and I can't find a decent diagram of the coolant flow for this 5.0 engine. Not even in my users manual. so, yes, pulling engine is on list of things to do....I am looking for temp fix for just using it in fresh water pond or lake till end of season.

I am going to pull my batteries today so I can crawl in there to get a better look at things this week.
 
Tahoe_User said:
I think coolant is getting up through higher part of block. see attached pic...the red circle is where the plug is that I think it the culprit. If I keep the boat I will pull motor but I think becaue the freeze plug is high in the block that it is getting coolant to the block.....however, I believe the coolant than is suipposed to go to the riser and manifold and I can't find a decent diagram of the coolant flow for this 5.0 engine. Not even in my users manual. so, yes, pulling engine is on list of things to do....I am looking for temp fix for just using it in fresh water pond or lake till end of season.

I am going to pull my batteries today so I can crawl in there to get a better look at things this week.
Click to expand...
the coolant needs to be up in the heads to cool valve seats otherwise they crack and burn valves.

You have spent more time talking about it than it would take to pull the motor. You only need to lift it and pull it up or forward enough to get flywheel cover and flywheel off. A freeze plug from the auto parts store or expansion plug will do it.
 
Dieter said:
the coolant needs to be up in the heads to cool valve seats otherwise they crack and burn valves.

You have spent more time talking about it than it would take to pull the motor. You only need to lift it and pull it up or forward enough to get flywheel cover and flywheel off. A freeze plug from the auto parts store or expansion plug will do it.
Click to expand...
yeah...I am very hesistant to pull motor because I feel like that will lead to like 30 mini projects...however, it does not look as bad as I thought. I will stand down my other plans and go rent an engine hoist and follow your direction and bondo's direction. Pics to follow. I am thinking if I am removing stern drive that I will replace impeller and do a few other bits and bobs while I am in there....like moving bilge pump etc
 
Back
Top