5.0 230 Mercruiser Manifold and Riser Flushing

[SeaRay Weekender]

Hi folks, I have a 1986 Sea Ray with a 5.0 liter 230 HP Mercruiser/Alpha 1/ raw water cooled. It has the 1st design type thermostat housing- 1 hose to each exhaust manifold, and one to each riser. If I were to remove the hoses from the thermostat housing, open the drains and put a garden hose into each hose to flush out the manifolds and risers- is there a chance the water would run back into the cylinders through an open exhaust valve? I would like to flush out these components as well as the block and hose to the gimbal housing as I suspect there may be some sand in there somewhere blocking coolant flow due to being grounded on a sandbar with the tide going out recently. I replaced the Impeller and Thermostat already and flushed the outdrive throroughly, but I've still got an intermittent random temperature fluctuation issue (acts similar to a slightly sticking thermostat). Thanks!

 

[achris]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

Remove the manifolds and elbows from the engine and flush them that way....

Chris..............

 

[tommays]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

I have managed to put a LOT of small stones from sand bars into my stat which has required changing it a few times

 

[SeaRay Weekender]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

Well, I was going to pull them off anyway for an inspection, might as well do it now. So, there is the possibility that flushing them with them still on the motor that water can in fact enter the motor through an open exhaust valve? Asking just for future reference. Of course, I will find out the answer myself as soon as I pull the manifolds and risers and see...
We rescued a large group of people on sunday night from a sinking 37' Cruiser that went down off Hampton Beach,NH around 9PM. I noticed coming in that the temp gauge shot up to just under 200, then came down a few minutes later to normal- around 145. Next day she warmed up to normal, cruising around all of a sudden it dropped to 130! (it never runs that cold), then up to 170, then back to 145- all within a few minutes time. I know it could be a gauge or sender problem, but all this has happened right after we grounded on the sandbar- so I'm thinking sand is blocking the coolant flow somewhere.

 

[Bondo]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

So, there is the possibility that flushing them with them still on the motor that water can in fact enter the motor through an open exhaust valve? Asking just for future reference. Of course, I will find out the answer myself as soon as I pull the manifolds and risers and see...

Ayuh,... I gotta disagree with Bubba,...

If All of the equipment is in sound condition,...
Force feeding water through the cooling system just Can't flood the cylinders thru a valve....

But,.....

Were it me, the very first thing I would do is pull the raw water pump apart and inspect it.

That's a Fact........

Sand will Eat a rubber impeller in No Time Flat....
Be prepared to replace the Housing too if it needs it....

 

[achris]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

So, there is the possibility that flushing them with them still on the motor that water can in fact enter the motor through an open exhaust valve? Asking just for future reference. Of course, I will find out the answer myself as soon as I pull the manifolds and risers and see...

Ayuh,... I gotta disagree with Bubba,...

Dang... I hate this... Now I gotta disagree with Bond-o...

If the elbow is off and the water flows into the exhaust chamber of the manifold, then YES, water WILL enter the cylinders through an open valve....

But I do agree about the water pump... Sounds a lot like either not enough water, or a crappy thermostat... Me? I'd just do a full annual service: oil and filter, plugs, points, leg off, new impeller... You get the picture....

Chris...........

 

[Bondo]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

Dang... I hate this... Now I gotta disagree with Bond-o...

If the elbow is off and the water flows into the exhaust chamber of the manifold, then YES, water WILL enter the cylinders through an open valve....

Ayuh,.... If the Elbow/ Riser is Removed,... Yes....

But,....
That isn't mentioned or stated above.....

I said,....

If All of the equipment is in sound condition,...
Force feeding water through the cooling system just Can't flood the cylinders thru a valve....

Force feeding thru the cooling system, That's Still Assembled,+ in Sound Condition.....
The water will exit the risers,+ fall into the exhaust system to be dumped overboard....
It can Not,+ will Not enter the cylinders thru the exhaust valves.....

Correct,..??..??

 

[achris]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

On the basis that nothing has been removed, yes, no problem, I do it all the time... Even run engines on a test stand...

 

[SeaRay Weekender]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

OK Guys- after removing everything to investigate and flush the water passages- there actually is a way that water can enter the engine through the exhaust valves. It should not happen if you pay attention though- these center risers are 3" with the 15 degree down angle. If someone was to try to flush them with a boat on the trailer with the bow down at or more than 15 degrees from horizontal, water would run out of the riser, and back into the motor through the exhaust valve.
The risers weren't in bad shape, just minimal scale- but for the piece of mind I'm just going to replace them. The ones currently on the boat are Aqua Power 5700's. I see Aqua Power is no more, having been swallowed by Sierra. I'm not a big fan of marine aftermarket stuff- prefer the factory Mercruiser parts. What are you guys' opinions of the Sierra or GLM risers vs. Mercruiser risers? I will also replace the impeller and thermostat, as I believe you are right- all it takes is a little sand. And those parts are cheap and easy enough to R&R anyway.

 

[chiefalen]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

And now i'll have to disagree, If they are good don't replace them. Check the t-stat.

You can back flush from the hose running to the t-stat back out the drive see what comes out.

While you have the t-stat cover off what you see. You have a power steering cooler. Thats where a blockage will occur.

Any heat exchanger could be a blockage.

 

[SeaRay Weekender]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

Don't get me wrong- I'm not changing them in the hopes that it will cure the temp issue- I know they are not responsible. They are in fairly decent shape, but they are also 7 years old and have been used in salt water their whole life. I don't want to take a chance on a pin hole leak starting. More of a PM thing.
I did backflush the hose from the thermostat housing back to the gimbal housing after disconnecting it there- it looked good, but I never thought to take a better look at that PS cooler for a blockage- thanks for bringing that up- I will take a look at it. I replaced the Impeller and T-stat last week prior to this issue- but I am going to change them again just in case either is defective.
I'm primarily looking for some feedback on the different Riser/manifold manufactures- GLM, Sierra, Barr, Osco, etc- to make sure I don't end up with substandard parts. Surprisingly, I did hear some negative on Mercruiser risers not lasting 1 year, that had me concerned.

 

[chiefalen]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

I know some people were having trouble with risers and manifolds. They were made in china.

I never heard any one having trouble with o.e.m merc. parts.

If bond-o sees fit to chime in maybe we can get his excellent advise.

 

[Uraijit]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

I've heard good and bad about GLM. Some folks have gotten crappy castings, and had to send them back.

Never heard anything bad about OSCO though.

 

[SeaRay Weekender]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

Thanks guys. I pretty much feel that everything you read on the web should be taken with a grain of salt, but this link is what had me concerned about Mercruiser Risers:
http://marinesurvey.com/yacht/exhaust_risers_1.htm
Now maybe this guy is also a major shareholder of GLM or something, I don't know. But ebasicpower on EBAY sells a complete set of GLM manifolds and risers for under $400. My worry is that GLM is simply cheap made in China junk, and I certainly don't want any of that. I'd much rather spend the extra money and get a quality casting from Mercruiser- if that's not a fallacy in itself.

 

[Uraijit]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

I boat in freshwater, so I don't have to worry about salt water eating aluminum. I'm planning on going with aluminum next time around.

I'd say just get you an OSCO set, and call it a day.

 

[SeaRay Weekender]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

Yep, the OSCO looks pretty good- so does Barr Marine- and both are made in America too. GLM is in fact made in China.

 

[Bondo]

Re: 5.0 230 Mercruiser Manifold and Riser Flushing

It should not happen if you pay attention though- these center risers are 3" with the 15 degree down angle. If someone was to try to flush them with a boat on the trailer with the bow down at or more than 15 degrees from horizontal, water would run out of the riser, and back into the motor through the exhaust valve.

Ayuh,.....

And Common Sense says that when the trailer is unhooked from the tow unit, you jack it All the way Up, Everytime.....
As long as you remember to pull the bilge plug,...
Nothing will Ever be Flooded....

Including the motor from flushing.....

GLM is in fact made in China.

Ayuh,... Sure are,+ they show it....

Search up the thread by Myself about them,.... Mine needed machining to use them,...