repower or repair?

[eseyoung]

As I mentioned in the a27 section, I need an mixing elbow for my ld28. Trouble is that parts for it are nonexistent. As others have said there is a fabrication shop who will make one but the trouble with that is I am looking at almost 1200 for one. Then I still have an ld28. Which is a a very uncommon marine engine, not real powerful, old, parts scarce, engine. So is now a good time to repower? I have about 2300 hours on it.

thoughts?

I have considered the idea of trying to make an elbow from a more common manifold work. There are several that, from the picture, look like they may work. I need to drill and tap the bolts anyhow (all4 of the old ones broke) so bolt pattern isn't a huge issue. Id have just about $150 in doing it that way.

[RobS]

Isn't this all you need at a price of $750? : viewtopic.php?f=28&t=6888&p=41706#p41706

[eseyoung]

Yes. But when I called the price has (apperantly) gone up.

It is just a matter of do I spend the $$$$ on the ld28 or move on to a yanmar, or maybe even drop a Lehman 120 in. Forr the later option I will have to do some research to see if it would work.

1200 just sounds like a good chunk of $$$$ to put into the ld28. Maybe not?

[RobS]

Oh, that stinks. Yes, I can see you have some decisions to make... Maybe John VB from the other post can sell you his old riser as it seems to still be serviceable and then you are up and running again and you have a running engine you could sell if you decide to repower.

[Treeman]

I still run an AD21 in my 25. The original exhaust elbow clogged and just seemed a really deficient design so I had a welder friend build a new one. It flows WAY better than the original and the outside of it stays right about body temperature and that's running in the bathwater-warm Gulf of Mexico.

[Tahoma]

I think Treeman is heading in the right direction. I paged thru the Barr Marine Manifold catalog and they may have something that will work with the addition of a custom built adapter. I'd measure the exhaust outlet on the Nissan manifold and call Barr Marine (100 Douglas Way, P.O. Box 190, Natural Bridge Station, VA 24579 Toll Free: (866) 255-9265 Phone: (540) 291-4180 Fax: (540) 291-4185) and see if they have some solutions for you.

I am not sure getting a hold of John VB's old part will work. One of the two photos shows the base of the old part intact and in the other it appears that one of the corners is broken off.

I have two old Nissan risers both with good bases and both with cracked water jackets at the outlet end. I'll take a look at them with an eye toward repair but: I'll not be able to get to them in about 10 days and I'm not optimistic that either one of them is any good.

P.S. It's hard to believe the price of the aftermarket unit has gone up almost 50% in 3 or 4 months!!

Jim

[eseyoung]

I wanted to give an update on this.

I have been reading a ton on how wet exhausts work. I had no idea before.

Either way i think i have a DIY solution now that i have a better understanding of how they work.

I have ordered 3'' tubing and am going to cut and weld up an elbow like this one. A major change in design is that the cooling water will be injected into the elbow much farther down the line, near the end where it goes into the rubber exhaust hose. IMHO this has a couple of advantages...for starters its an easier build. Also, this will make it very much unlikely to flood the manifold with sea water if a failure occurs. I will put some heat wrap on it to prevent having a hot section of pipe.

The flange i am just going to cut out of a section of plate...not a huge deal either.

The tubing i am going to use is just mild steel tubing but i think it will last more than a few years (the old lasted 18 years and it was cast). i plan on giving it a coat of exhaust paint both inside and out. I would have liked to use stainless but my welder won't weld it. I suppose i could have had someone do it...

[denchen]

Hi eseyoung, just to try and help you with your project, I have fitted a proper temperature pick up 6 inches down the rubber exhaust after the metal elbow on my boat. My engine is only a slow reving 1800cc diesel, so will be different to yours, but, the highest temperature I have ever seen on the gauge is 21oC. I ran it up the other day to charge the batteries and it only got up to 9oC. Needless to say the exhaust past the water outlet does not get at all hot. To weld stainless with an ark welder is the same as mild steel except you need stainless rods.

[eseyoung]

Thanks for the help. I did have a concern with the idea of having the pipe uncooled from the flange to the point of the water injection. A friend of mine has a car with headers wrapped in the insulation tape his pipe near the flange (not wrapped) gets glowing hot, but 3 inches where it is wrapped away it is cool enough to touch. I was also concerned about the point of injection not distributing the water enough to cool the passing gases. I have looked at other DIY risers and they don't seem to have a problem with this. I will 45 cut and saddle the injection nipple to disperse the water as much as possible.

the flow on the old one had to pretty much nonexistent and i didn't have any issues either with general engine over heating or with exhaust damaging the rubber hoses/elbows.

it was only after another member convinced me to check mine by removing it from the manifold that i discovered a problem.

[jleonard]

Hi eseyoung, just to try and help you with your project, I have fitted a proper temperature pick up 6 inches down the rubber exhaust after the metal elbow on my boat. My engine is only a slow reving 1800cc diesel, so will be different to yours, but, the highest temperature I have ever seen on the gauge is 21oC. I ran it up the other day to charge the batteries and it only got up to 9oC. .

90 C (194 F) is pretty hot for an exhaust IMO. esp at idle. Mine is nowhere near that temp measured from the outside. I usually see around 55-60 C (130-140 F).

[denchen]

Not 90 oC. But 9......oC. There is a max warning sensor that I have set to 65 for the audible alarm to go off

[eseyoung]

Between shoveling snow and trying to stay warm I had a chance to fab up the elbow. It is as I planned, made of 3inod steel tubing. The flange is 1/8 plate and the water injector is sch 40 3/4in iron pipe. I painted the whole thing, inside and out with high temperature paint and wrapped it in header wrap. I deliberately made the water injector look out to the side abit so I didn't have the heater hose going over top of the elbow.

[eseyoung]

Onee more pic. Any thoughts or feedback?

[jleonard]

Onee more pic. Any thoughts or feedback?

I would have liked to see it without the header wrap to see how it's constructed.
I do like that you put the water inlet downstream.
Let us know how it fits and functions.

[eseyoung]

To give a final up date on this i did install the elbow and it works great. I will be sure to post some pictures when i get back to the boat this weekend. I ran it about 2 hours so far and no signs of leaks or over heating of engine or exhaust components.

As for the construction...it is just cut on a chop saw the 90 is cut at 2 45deg angles and the two 45's are just cut at 22.5degrees on each end. All parts are then just welded together. the cut for the water injection was done with a hole saw....and the stub is a 3/4 pipe nipple cut at 45degrees.

If i had it to do over again I would have brought the water injection nipple down on the side more and maybe cut the angle a bit sharper so there isn't so much kink in the heater hose. but it works as is.

Total cost was $60 for steel, i only actually used half of it, i could very easily build another just out of my left overs.
$20 for a spool of flux core welding wire....yes i used an entire spool
$5 for heater hose.
$10 Fiberglass exhaust wrap
that is $95 total

Tools used:
cheap flux core welder from Harbor Freight
Cheap chop saw from the same
Drill
hole saw set
Tap and drill bits to retap the broken off bolts

As for time...i spent a ton of time reading about how wet exhausts work so i could understand what the part i was making actually did, but the actual construction time was about 2 hours and an additional hour to install it (drill and retap) on the manifold.

so all told 3 hours and $100...who says boating can't be affordable?