How do we prevent riser gasket leaks?

[HT32BSX115]

I'm sure this is a common problem at one time or other.


This engine (460 FORD/OMC) ran good and operated many years with little maintenance.(probably the biggest problem here)

My brother bought it new, only used it in fresh water lakes and never left it in the water for more than a couple of days.

It appears that the riser gaskets started leaking 3 or 4 years ago and since he didn't know they were leaking, just kept running it.

After shut-down a small amount of water would run back into an open exhaust valve and would sit there until it was started or it would slowly run by the pistons into the crankcase. (Of course this would take some time....causing rust in the cyls if it sat for the winter) When I got it it would act like it had a hydraulic lock if you tried to start it within 10 min or so of shut down.....If you started it almost immediately after shut down it would start right back up (with only a *Little* hesitation as it tried to comress that little bit of water in the cyl) If you waited 10 min or more cranking would stop at the cyl that had water in it. (I initally thought the battery or starter was bad!) I'm not in there yet but it may have a bent rod too.


The manifolds and risers appear to be in very good condition since they were replaced at one point several years ago. The boat was never left in the water and was only used 25 or so hrs each summer.

The gasket sealing surfaces are not in very good condition so I'm going to mount them on a vertical mill and take off enough to clean them up so the new gaskets have good clean surfaces to seal to.

Is there a good sealant that works well with riser gaskets to prevent this in the future?


Thanks,


Rick

 

[Bondo]

Re: How do we prevent riser gasket leaks?

Well Rick,.......

IF the Gasketed Surfaces are in Good Shape,........
Any Sealent is un-needed............
That's what the Gasket is for.......

If the surfaces are in Bad Shape,..........
Any Sealant is just a Band-aid................

 

[Don S]

Re: How do we prevent riser gasket leaks?

I would also be careful of machining down the manifolds and risers. I know both Volvo and Mercruiser only allow .010" max for machining. The reason is the way the riser contacts the hose going to the exhaust Y. And it can create hot spots and burned holes in the hose if too much is machined off.
Usually the cause of that gasket surface degrading is sealers. That is the reason both Volvo and Merc used the graphite covered gaskets. Volvo has now went to a metal gasket. It's a little touchy to install, but the edges of the manifolds and risers seem to last longer. BUT, you don't have that option with your OMC

 

[imported_rosco]

Re: How do we prevent riser gasket leaks?

change the riser gaskets every year when you inspect them. they are cheap.

replace then every 4 or 5 years, 3 to 4 for salt water. its not the gaskets that leak ususally, its tiny little pin holes from rusted cast iron up in the risers themselves.

now the bad news.

water in the cylinder during a compression stroke at high RPM,s can actually bend a connecting rod. i know from first hand. not to mention destroy your rings over a relatively short period of time, to the point oil will be sucked up into the cylinder and make it look more like a 2 cycle than a 4 cycle engine.

more bad news.

its not usually the risers that go, people usually replace them. its the heads. the metal between the exhaust ports and water jackets is THINNER than the cast iron in the risers. if the risers needed to be replaced because of corrosion, you can bet, the heads did too. they get tiny little pin holes in them and dump water into the cylinder, usually when you shut the motor off.

that "vapor lock" you get when its hot? its not your starter. its not your battery. it is the rusted remnants of your rings getting wedged against your cylinder walls when the piston expands in the cylinder when it is hot.

the motor is done. sorry. been there myself a few times.

do a compression check before you waste money on risers. and if you buy new risers, you will still get milk shake in your oil. when you do, you can believe me then. its the heads.

if you decide to rebuild, which you may change your mind about when you see the condition of the head bolts that sit in the water jackets.....TOSS the heads. do not rebuild the heads. try and find a place that does "exchanges" for valve jobs and unload them on them.

even if you have them magnifluxed, and dont find any leaks on one of them, it is just a rust flake away from failing on you. ask me how i know.........

 

[Autotech1]

Re: How do we prevent riser gasket leaks?

He didnt say anything about vapor lock. hes talking about hydro-lock. thats water in the cylinder. water doesnt compress, and thats exactly what it is. Rings could be in a hundred pieces and rusty, and theyre not gonna stop a motor dead in its tracks.

Hydro-lock will.

I agree with the heads, when your talkin about salt water. Doubt it in fresh water, and if he has a fresh water system than your telling him his good heads are junk.

ask some questions before telling someone he has garbage.

 

[Bondo]

Re: How do we prevent riser gasket leaks?

Man,........ Where do you come up with this $h!t...........

water in the cylinder during a compression stroke at high RPM,s can actually bend a connecting rod.

Reversion Never happens at High rpms,.... The Exhaust Flow is sufficient to Keep the Water downstream......

that "vapor lock" you get when its hot? its not your starter. its not your battery. it is the rusted remnants of your rings getting wedged against your cylinder walls when the piston expands in the cylinder when it is hot.

Who said Anything about Vapor Lock,..??..??......

Rick appears to be a guy who Isn't scared of a Wrench,....
He's Already figgured out Why it Cranks Hard at times......

the motor is done. sorry.

That Seems to be Your Regular Answer to Everybodies Issues.........

Maybe you didn't Read the part about this being a Freshwater Motor.........
Not 1 of Your South Florida Saltwater motors.......:%

 

[imported_rosco]

Re: How do we prevent riser gasket leaks?

hate to disagree with you bondo, but i trashed two 454s fresh from a rebuild because of water intrusion. and when i pulled them apart, i had 2 rods in one motor and one in the second bent at the wrist pin. that is a common place for it to happen to, its the weakest part of the rod.

and water in a good cylinder will stop a piston, but water in a cylinder that has had its rings trashed over three years will quickly be pushed into the oil and not lock the motor up.

a combination of the heat, the corrosion, the iron from the rings and the oil leaking into the cylinders creates a shelack type substance in the cylinders. while it is hot and running it will be more fluid and not bind the motor up. after you shut the engine down, it becomes like paste and glues the piston to the cylinder walls after a few minutes. when it cools, it becomes britle and will break when the starter turns and free up.

eventually, enough will build up to freeze the engine completly. liquid wrench will free it up again, but your cylinder is being destroyed during the process.

fresh water, salt water, doesnt make any differance. just happens faster in salt water. dont believe me, experiment for your self. go hang a piece of cast iron on your back porch and spray it wilth water once a week and watch what the inside of your motor looks like happen right before your eyes.

do a compression test. it will tell you whats going on.

and i promise you, water can and will bend a rod at high rpms. even forged rods. i have seen it happen first hand.

you have nothing to loose. if the compression test shows you have a couple bad cylinders, take it apart. if you cant see anything wrong with the risers, have the heads magnifluxed, it doesnt cost much.

and if you decide to rebuild, the block will be ok, but replace the heads. if you find a bent rod, check the berring surface on the crank very carefully. use a micromitor, have them ground if necessary. it doesnt take much of a dent or uneven wear to spinn a berring.

not here to argue with anyone though, just trying to save you alot of time.

do a compression test. if it checks out, your good to go. if not, stop worring about your riser gaskets.

 

[Don S]

Re: How do we prevent riser gasket leaks?

hate to disagree with you bondo, but i trashed two 454s fresh from a rebuild because of water intrusion. and when i pulled them apart, i had 2 rods in one motor and one in the second bent at the wrist pin. that is a common place for it to happen to, its the weakest part of the rod.

You might have lost two engine because you tried to start them too many times, but you didn't bend rods from a water leak from the manifold/riser gasket leak or any kind of a leak into the exhaust side of the manifold or riser from the water side. The exhaust itself would push the water out.

You obviously have a lot of political speech making experience. You make very long replies that have few documented facts, and reference things you obviously no little about, including a lot of really false/incorrect information, and never really say anything constructive, useful or helpful

 

[Scaaty]

Re: How do we prevent riser gasket leaks?

operated many years with little maintenance.(probably the biggest problem here)

This could be the problem...boats aint twist the key and go like cars..

 

[Autotech1]

Re: How do we prevent riser gasket leaks?

I have to agree with DonS. cranking a motor over full of water is the only thing gonna bend a rod. That and dumping a bucket of water down the carb of a running engine.

Water WILL NOT go past rings fast enough to let it keep spinning either. Its called fluid dynamics. Yuo could drill a half inch hole in a 454 piston and water would still not go thru fast enough.

yes you leaked water rosco. Yes you bent rods. But no, you dont understand the relationship between the two.

You cannot base a theory on one experience and label it fact.

 

[HT32BSX115]

Re: How do we prevent riser gasket leaks?

operated many years with little maintenance.(probably the biggest problem here)

This could be the problem...boats aint twist the key and go like cars..

I would say that this is the MAIN reason for this problem!

I know my brother basically had someone else do the work....what little was done... In the last 2 times he had a FourWinns dealer do it once and and they also did the drive maintenance. On this one they didn't bother to put any oil in the drive.......They of course replaced the drive.

He decided to take it to a different dealer the next time and they did the same "service" except when refilling the drive they didn't fill it from the correct port and caused a big bubble at the top.....The drive made it a little further than the last time but not much further! They too replaced the drive. They also kept his service manual and I had to buy one!


I did replace the intake manifold gaskets at the beginning of summer thinking I had a vacuum leak.......The gaskets were truck engine gaskets and they were pretty much crumbling. I rebuilt the carb too but it was absolutely clean inside.

I also at that time did a compression check and got 160 psi on one and 165 or higher on the others so the cyls weren't all that bad......

Now that I have the heads off I have noticed that only 2 cyls (1 each side)are pitted pretty badly and it's clear that water sat in those cyls for 1 or more winters but I must conclude that it's not bad enough yet to cause loss of compression. It WILL take more than 0.030+ boring to clean them up though.


The main problem (of why I wasn't getting full WOT RPM)was the cam has several flat lobes!


It wasn't a poor breakin since it ran good (5000 WOT/60mph) for several years.

My brother also told me that he put Slick-50 in it!

I guess I could be one of those testamonials that claim that Slick 50 didn't hurt my engine so it must be doing something good!!!! (oh......wait:%.....my cam went flat!!!!......let me rephrase that!!!!)



So We'll see .......I will be rebuilding it. I'll do my own maintenance, (I probably won't use Slick-50 :} )



Thanks Don, for the info on machining risers/manifolds. I have a little more wiggle room on mine since I have more hose and the diverter valves in the exhaust system. If those weren't there I wouldn't have much room to work with.

As it is I'm only going to remove enough metal to clean them up. They aren't pitted.....they might even seal as is but I'd like shiny surfaces to seal to. I don't think I'll have to take off more than 0.010" on each surface anyway.



I'll let you all know if any of the rods are bent. (I was going to replace them all anyway)


Regards,



Rick

 

[imported_rosco]

Re: How do we prevent riser gasket leaks?

You might have lost two engine because you tried to start them too many times, but you didn't bend rods from a water leak from the manifold/riser gasket leak or any kind of a leak into the exhaust side of the manifold or riser from the water side. The exhaust itself would push the water out.
--------------------------------------------------------------

yours is theory. mine is experience.

but, ill take you through the sequence of events as they happened.

tested boat at home, both engeins up and running fine. launched boat in water, ideled out of 20 minute long channel, both engines running fine. reach end of channel, and slowly power up to a slow plane, both engines running fine. after 20 minutes of crusing, inched the power up to a moderate 3500 rpms, doing fine. 20 minutes of that, inched it up to 4000 rpms.

5 minutes into 4000, all hell breaks loose. engine goes from fine, to rods ticking to rods sl;amming against the cylinders in less than 30 seconds. powered down before i realised how far out i was, then immediatly got back into it in a charge for the channel. motors were toased, diodnt want to add insute to injury with a 400 dollar towing bill.

never shut the engine off to have to restart it.

got home, pulled the motors 3 days later, and two cylinders in one engine was full of water, and one cylinder in another was full.

manifolds and risers were brand new.

found holes in the exhaust ports of the heads where the cylinders were full of water that were not there before. i know that for a fact, i had the heads magnifluxed before rebuilding them.

just some rust spots that let go after the engine was up and running.

how many of you have bent a rod in a boat due to water intrusion or any other reason for that matter?

theory is fine, but sometimes sheit happens that doesnt fit into your nice little world you create for yourselves.

granted, one of the engines had blown all the head bolts loose, ie, pushed them through their threads, but weather that was done BEFORE the water intrusion, or was a result of the water intrusion, both of us can only guess.

however, the heads on the second motor were still torqued down, so loose head bolts will not explain both engines. corrroded water jackets do. water intrusion while the engine was running is a certainty, inspite of your "exhaust will blow it out" theory.

you get anough water leaking into the exhaust, the exhaust will seek the path of least resistance, and blow around and past the water, leaving the water to fall into the cylinders. basic dynamics of air/water flow. heavy sinks, heated gasses rise. short of enough exhaust pressure to completly fill the entire exhaust system full of enough air pressure to lift the weight of the water, its gona go down, not up.

simple test to give you a better idea, full a funnel full of water, and blow on the end of the neck and see if you can get ALL the water to go out in one breath, or compression stroke as it is. then try it with a straw.

why the differance? because you can put out anough pressure through the straw to completly fill the entire volume of the straw with enough pressure to life the water. but when you do the funnel, you do not have enough breath to completly fill the volume of the funnel.

engine companies go to great lengths to make sure the exhaust of any given engine has greater volume than the engine is capable of producing to reduce back pressure as much as possible so as not to impede performance.

there is science to prove why your theory is wrong. at best, you can only hope a small enough quantity of water is leaking that it will get vaporized during the combustion. but i guarentee you, the water is going down, not up.

but like i said, im not here to argue, just to enlighten. believe what you will.

experience is always a better teacher than theory.

 

[Haut Medoc]

Re: How do we prevent riser gasket leaks?

http://cgi.ebay.com/460-FORD-OMC-46...ryZ26451QQrdZ1QQssPageNameZWD1VQQcmdZViewItem


You could try these!.......JK

 

[180shabah]

Re: How do we prevent riser gasket leaks?

OUCH!!!
$3000.00 for a set, I think I would take my chances on loosing a motor8)

 

[Autotech1]

Re: How do we prevent riser gasket leaks?

Im not going to argue either, because it sounds like youv'e got yourself thoroughly convinced yours is the right diagnosis.

Also I wonder what your occupation is. Are you a mechanic?

Big block chevy heads are very restrictive and are the bottleneck of most BBC motors. A 4 1/4" by whatever stroke will easily blow an exhaust port clean.

 

[180shabah]

Re: How do we prevent riser gasket leaks?

I must admit, I have never tried to blow water out of a funnel. Unlike, an engine, I do not have the ability to develop 150psi either, Guess I will have to stick to blowing water through straws..

 

[olbuddyjack]

Re: How do we prevent riser gasket leaks?

Big block chevy heads are very restrictive

460 heads are even more so.

 

[rodbolt]

Re: How do we prevent riser gasket leaks?

if you were not so far away I have a fwc 460 with a 2/1 borgwarner that was a running take out thats gonna get scrapped shortly.
have not started it in a year or year and a half though.

 

[HT32BSX115]

Re: How do we prevent riser gasket leaks?

Thanks!

I am just going to rebuild this engine. There is an absolute WEALTH of info on rebuilding 460s out there. They have been using 460's in marine appliactions for years and still do in jet boats.

I sure I can build this engine to immediately spin the coupler on the first WOT run! (that'll be wonderful...for about 2 seconds!).

I considered stainless steel headers from this company. http://www.boatheaders.com/460 ford.htm

These are not "dry" water injected headers. They're water-jacketed headers that can be custom built for any application. They would work in an enclosed compartment unlike dry headers that would absolutely set the boat on fire in short order!!

The down side is they're about $2100....Towards the end of 2005 Doug Russell had the 460 OMC manifolds listed for $995 EA! (excl risers) So maybe this isn't so bad after all and these are performance headers with the risers built in. I may add FWC when I do the rebuild. I don't even think I'll use this engine. I may find myself a low mileage D0VE 460 block so I can start with minumum cooling sys rust.


Thanks for the info guys!




Rick

if you were not so far away I have a fwc 460 with a 2/1 borgwarner that was a running take out thats gonna get scrapped shortly.
have not started it in a year or year and a half though.

 

[Bondo]

Re: How do we prevent riser gasket leaks?

Rick,.....

I can't remember Where I've seen them,....
But Somebody is marketing Adapter Plates for those 460s to run BBC Manifolds on them,......
The only down-side I can see is it makes the motor about an Inch Wider.......