Direct seawater cooling question.

[LX Kid]

Have an '82 G-White with Mercrusier 305. Since and before I bought it, it has been used with direct seawater cooling thru the block. When returning from boating I always flush system with fresh water. I know that fresh water cooling system is most desired but "it is what it is!" Just wondering what the engine's longivity could be? Is anyone else have any experience with this and how long did your engine last? Thanks

 

[Lyle29464]

Re: Direct seawater cooling question.

It's too late to change your system. It would plug up. Closed cooling lets you run antifreeze in your engine block and maybe your manifolds. This will alow you to keep the same engine for many years. Front water pump will last much longer. You still have sea water in the exchanger and your risers. You should flush that out after boating. You still need to drain part of the system in case of a hard freeze. It runs about $1200 more than an "open" system.

 

[Don S]

Re: Direct seawater cooling question.

Manufactures do not recommend installing a FWC system if over 125 hours or 1 years use. I would bet that 228 is way over both.

 

[Bondo]

Re: Direct seawater cooling question.

Have an '82 G-White with Mercrusier 305. Since and before I bought it, it has been used with direct seawater cooling thru the block. When returning from boating I always flush system with fresh water. I know that fresh water cooling system is most desired but "it is what it is!" Just wondering what the engine's longivity could be? Is anyone else have any experience with this and how long did your engine last? Thanks

Ayuh,..... They usually last til the exhaust riser fails, dumpin' seawater into the cylinders....

It's an awfully Old motor, that the actual block rots away....

 

[LX Kid]

Re: Direct seawater cooling question.

Running on borrowed time I guess. Good thing there are lots of good used engine down here in Florida. Lot's of people bailing out of boats due to fuel costs and the economy.

Might be a good idea to change riser gaskets every two seasons and do a visual inspection/cleaning.

 

[LX Kid]

Well it's been couple years since I started her up and I did just that today. The fuel inlet needle was stuck and after a little tapping she started right up! After getting up to operating temp, and beyond, I figure the heat riser is once again plugged up with rust. Gonna try and pull them off and clear passages this weekend. Block still hasn't rusted thru into the cylinder, yet, and she runs pretty good. Guess the old ignition switch is bad cause I had to start it doing a jump across the starter relay terminals.

 

[thumpar]

Since it has been a couple years it could easily be just an impeller that need replaced.

 

[achris]

Since it has been a couple years it could easily be just an impeller that need replaced.

I concur.

 

[JoLin]

Re: Direct seawater cooling question.

Running on borrowed time I guess.
Might be a good idea to change riser gaskets every two seasons and do a visual inspection/cleaning.

Hold on. Raw (salt) water cooled engines require replacement of exhaust manifolds and risers every 5-8 years. As Bondo said, it takes a LONG time for a block to rot through. The engines generally fail beacuse the mani's and/or risers rotted through, allowing water to enter the engine. A visual inspection of the risers will tell you nothing about the condition of the exhaust manifolds.

If you don't know when the exhaust manifolds and risers were least done, or they're old, replace them. Why lose an engine?

 

[LX Kid]

Hold on. Raw (salt) water cooled engines require replacement of exhaust manifolds and risers every 5-8 years. As Bondo said, it takes a LONG time for a block to rot through. The engines generally fail beacuse the mani's and/or risers rotted through, allowing water to enter the engine. A visual inspection of the risers will tell you nothing about the condition of the exhaust manifolds.

If you don't know when the exhaust manifolds and risers were least done, or they're old, replace them. Why lose an engine?

Could be some good advice. I'm going to pull both off Monday and will try and remember to take some pics. I'll look around for some better ones than mine. Last time I twisted and metal coat hanger and put it in a drill to break things up inside the passages and worked pretty good. Here's a pic of the after cleaning when I did it last time in July 2010.

 

[JoLin]

Doesn't tell you how much of the casting walls are gone, if some area is about to fail, or if any of the internal passages are clogging with rust. You can't tell the true internal condition of a manifold without a fluoroscope.

I'm telling you that salt water boaters MUST consider mani's and risers to be regular boat maintenance items. They require periodic replacement, not just visual inspection. If you're seeing no gradual rise in engine temp and you're using OEM (Mercruiser) parts you can probably get away with the 'far end' of the replacement cycle, say 8 years. Unfortunately, it's part of the cost of ownership, like replacing the outdrive bellows and changing the oil.

My .02

 

[LX Kid]

Doesn't tell you how much of the casting walls are gone, if some area is about to fail, or if any of the internal passages are clogging with rust. You can't tell the true internal condition of a manifold without a fluoroscope.
My .02

Yes I'm sure your correct and I'll make every effort to not be so "cheap" about getting some new ones! They are probably original from 1982. Might just have to wait until next Loto results though! LoL Still gotta pull them off to see if I have 3" or 4" risers. I think they are 3" ones.

 

[achris]

... Still gotta pull them off to see if I have 3" or 4" risers. I think they are 3" ones.

Risers or elbow outlets? I don't think you have risers on that engine.

 

[LX Kid]

Risers or elbow outlets? I don't think you have risers on that engine.

I looked them up on-line at go2marine and they call them exhaust risers for $109.00 each. I'll be taking them off tomorrow morning and see what condition they are in. (visual inspection)

 

[thumpar]

It doesn't look like you have risers just elbows. Risers are used when the engine is low in the hull to get the exhaust elbows above the water line. It looks like your elbows connect directly to the manifolds.

 

[LX Kid]

Pulled my Osco 8503A elbow/riser off this morning and believe I'm going to have to buy new ones. "Unless" someone can clue me in on how to remove the rust blockage on the outlet side. There is just too much scale built up around the outside of the exhaust center tube. I tried using a hacksaw blade with not much luck. Yes I know I "could/should" replace them but if I can clean them I would save about $300. Has anyone had any success with acids to boil the scale off and get unrestricted water flow thru the outlet side?

 

[LX Kid]

Forget about cleaning the elbow risers! I just pulled off the other one and it is totally plugged up. Gonna go ahead and buy couple new ones. There are basically two different gaskets. One has two elongated holes and the other has four elongated holes. Which would be best? One will restrict more water flow than the other. Because I'm using sea water cooling, no heat exchanger, I'm thinking the two elongated hole gasket. Opinions please.

 

[LX Kid]

Ordered the two hole restricted gaskets.

 

[achris]

Which sep plate depends on how the hoses are plumbed. Post an overview photo of the engine and we can see how the plumbing is. If you put the wrong one in, engine will overheat...

 

[LX Kid]

Which sep plate depends on how the hoses are plumbed. Post an overview photo of the engine and we can see how the plumbing is. If you put the wrong one in, engine will overheat...

See (#1) this post for the picture of hose routing.