No Water coming from exhaust

[AirBoyzT]

So on my last trip I started the engine and very little water sputtered out of the exhaust. I have a Volvo Penta 2002 18hp. I checked the impeller and replaced it (even though it was fine). I opened the thru hull and water poured into the straner as well as out of the impeller housing, so no clogs there. I am now going to trouble shoot.

I believe it is either the exhaust elbow is clogged or the heat exchanger is clogged. My local marine mechanic said it was most likely the exhaust elbow, as hardly any water is coming out and if the heat exchanger were clogged, it would be more water coming out.

Couple questions.
1) What's the best way to clean the exhaust elbow out
2) If it's the heat exchanger, what is the best way to clean that out. I've been told radiator shop, however, how hard is it to remove the heat exchanger to take it to the radiator shop to have it boiled out.

I appreciate it!
-Aaron

[Neptune's Gear]

Hi Aaron,
I have the 2003T, but it's basically the same motor, with another cylinder and a turbo.
First thing is that sometimes the impeller looks fine, but under load actually fails to turn. So good that you replaced it!
Take the exhaust elbow off yourself and clean it - its not too hard to do and will save you some $. If you stick a screwdriver through it when chipping off the soot and rust, it was knackered anyway - you should not be able to damage it like that anyway! Make sure the water injection port is clear, these block fairly commonly.
So, it has a heat exchanger?? Many of these are just raw water cooled, so no heat exchanger present. Raw water cooled ones sometimes have the block filled with sand and mud.
Presuming it is fresh water cooled, and has a heat exchanger, it will also have an oil cooler, in behind the heat exchanger. The oil cooler has smaller tubes than the primary heat exchanger, and these can be totally blocked with growth. It is good proactive to remove both the oil cooler and heat exchanger, and mechanically clean them every year or two. I use a .22 rifle cleaning brush for mine. No need to pay someone, although if it is really bad, it might be easiest to take it to a radiator shop or engine rebuild place and have it acid bathed. Once it's clean again, keep it clean!!
Also, in the copper tube that goes from the thermostat housing to the exhaust outlet, there is a small plastic fitting. Yes, in side the tube. It should have a pinhole through it - if it does not, the engine will overheat. The pinhole is prone to blocking...

It takes me about 3 hours to remove, clean, and reassemble the oil cooler and heat exchanger, and an hour to put them back on..

Cheers
Matt

[onestepcsy37]

heat exchanger. they usually have four hoses going into them - two are freshwater in and out, other two are seawater in and out. there is usually a bracket holding it in place. remove the hoses and the bracket and you've got a heat exchanger in your hand.

it will have one, but sometimes two, removeable end caps, which are usually held in place by a central bolt but may have another arrangement. back out the bolt and pry off the end cap(s). save the gasket(s). look inside and you will see a multitude of what appears to be small tubes welded together side by side. these are the tubes through which the seawater passes. freshwater passes around the tubes.

the tubes will probably be clogged, maybe a little, maybe a whole lot. i've been able to rod them out using a wire coat hangar (hard to find nowadays) but any thin rod that can hold it's shape will work. be careful when rodding - you don't want to poke a hole in a tube as it might allow seawater into the freshwater system. then flush it out with a hose. there may also be a zinc screwed into the side of the case. change it out. then put it back together.

it is possible that after inspecting the heat exchanger you decide it's long past it's useful life. in that case just bite the bullet and buy a new one.

elbow. sometimes referred to as 'mixing elbow'. it's where the outgoing seawater from the heat exchanger is 'mixed' with the engine exhaust. they are nearly always made out of cast iron and they eventually clog up/rust/disintegrate/die. if it's really bad the engine won't start because it's exhaust gas will back up into the engine. i always wondered why they used mixing elbows until a mechanic made it so plain and simple i wondered why my brain didn't fathom it before.

the exhaust 'pipe' after the mixing elbow is rubber. if engine exhaust were allowed to flow through it the rubber would melt and maybe burn. so the seawater, even though it's been heated after running through the heat exchanger, is used to cool the exhaust gases to a level the rubber can handle. simple.

you can start by removing the exhaust hose from the elbow and inspecting it's interior (elbow). if the elbow is is very very good condition i would just clean the elbow out with a screwdriver or some such tool and put the rubber hose back. if the elbow is in less than very very good condition i would probably replace it. you will need to unscrew it from the engine exhaust manifold or manifold pipe. can be a really thankless but necessary job.

all of the above notwithstanding, it's nice to know that the job is not all that difficult and will save you a couple of hundred boat bucks if you can do it yourself.

[Jim Cate]

One other possibility: sometimes the cover plate on the raw water pump wears, and the extra clearance on the sides of the impeller causes a loss of efficiency. Have a look at the inside of that cover plate and see if there are a lot of grooves worn in it. Many pumps have symmetrical covers, and so you can simply clean up what was the outside of the (usually brass) plate and reinstall it "inside out"for a quick fix.

Cheers,

Jim

[onestepcsy37]

having made the above lengthy post i see matt has a similar engine and probably a clearer understanding of your particular situation. so i defer to matt.

i have a perkins 4-108. it also has an oil cooler. i've never had any problems with it so i've always left it alone. particularly because, in the perkins engine repair manual, it states that perkins have discovered that the oil cooler isn't really needed and, if it leaks, you can just plumb around it....

[roverhi]

Check the water intake. sometimes things crawl in set up house or die plugging the seacock. Would've save myself a visit from the mechanic and overheating the engine if I'd checked that first.

[Jim Cate]

Originally Posted by roverhi

Check the water intake. sometimes things crawl in set up house or die plugging the seacock. Would've save myself a visit from the mechanic and overheating the engine if I'd checked that first.

Peter, the OP did those checks as mentioned in his first post.

Jim

[SkiprJohn]

Originally Posted by roverhi

Check the water intake. sometimes things crawl in set up house or die plugging the seacock. Would've save myself a visit from the mechanic and overheating the engine if I'd checked that first.

Yes, although he's done that check I had a friend who had to remove a couple fish from his Volvo seawater intake. Saltwater cooled engine. Easy to work on. Could be hand started (if you're young enough).