Exhaust Riser: talk me out of this!

[Adequate]

Greetings everyone. I've been a member for a while but this is my first post.

I've got a pair of Hino 4 cylinder engines with original exhaust risers. One has developed a cracked on the inner wall at the bottom. The other has a hole on the inner wall at the bottom. Because of the location of each deficiency, there was no chance cooling water flow could damage the turbos. I found the issues while replacing the exhaust hoses.

I was preparing to replace (build) new ones but I had a thought, maybe not a good one though.
Since the outer wall of the riser is perfectly good( with about 3/16" thickness) and the inner wall is 90 % in tact, why can't I run them dry and just add a mixer on the end of them?

I've had a knowledgeable individual advise against, saying it would get too hot. My intention was to wrap each in fiberglass exhaust insulating material. I'm able to make new ones, I'm just wondering why, if I can continue to use what I have.


For background, my cruising habits are not long distances. Mostly day trips or weekend overnight.

Thank you!

 

[Adequate]

A couple more pics.

 

[mvweebles]

I don't have enough knowledge to add more than armchair observation to your question, but I did a quick search on Marine Exhaust of Alabama (MesaMarine.com) and see the carry some Hino exhaust parts. Have you tried sourcing replacements? Guessing they are expensive which is why you want a workaround....

Online Catalog

Good luck -

Peter

 

[DavidM]

It could work, but the existing risers would get much, much hotter than they are currently operating with water cooling. That could lead to thermal expansion cracks.

David

 

[O C Diver]

As a point of reference, all the custom exhausts I see with the raw water added at the end and the rest is wrapped in heat resistant epoxy, are either stainless steel or steel. I'm guessing temperature stability is more important with cast iron.

Ted

 

[rslifkin]

Cast iron can work for a dry section (it's done all the time in car and truck exhaust manifolds), but I'd be worried about using something with a water jacket cast in that was designed for wet use in a dry application. The water jacket plus possibly thinner construction in some areas (due to lower expected temperature) could lead to a short lifespan if run dry.

 

[Adequate]

All great responses.

The total cost of replacing both engine risers and adapters is approximately 2300. Add to this 4" exhaust hose (my original project) and several other preventative maintenance items...things add up quickly. So it is purely a cost/time saving thought. Enough to get me through another season. Then next year build new ones....but I don't want to burn the boat to the waterline in the process.

If it were to fail, I would hopefully get no more than an exhaust leak, no water intrusion.

I'm not convinced one way or the other about this idea yet so keep the thoughts coming.

 

[KnotYet]

My takeaway from your situation is to be happy that you found the fault(s)
before any damage was done. I would shop for replacements and feel lucky!

Remember, fabricating two new post-riser mixers will not be cost-free either.

 

[Cigatoo]

Replace with Stainless from a reputable shop such as the one in Alabama. One and done. A poorly designed exhaust system can do a lot of damage to you and the boat.

 

[Solly]

Time to bite the bullet. The old ones are failing. What guarantee do you have they won't go completely ?? Possible heat, water, and exhaust gas inside the boat.
Buy now and be worry free.
Either replace with the stock risers or have new elbow's fab'd up. I don't see any big problems with making up a SS elbow. Sure it'll get hot but can be wrapped.
Replace with stock, they worked b-4, they'll work again. Fab something up and maybe... What's your risk tolerance ??

 

[Bmarler]

every single time you tear into a system on a boat you should be prepared to either quadruple the budget or toss it out completely. having a solid exhaust system isn't an option, it's a requirement. there's no way i'd consider running those when they're 1, already damaged, and 2, dry when they're supposed to be water cooled.
the castings are engineered to be water cooled and are much thinner than manifolds that are for dry exhaust. i totally get the pain of the cost, but if those let go, it'll never be at a good time. things can happen in a tight channel with the current running hard.

 

[Adequate]

You guys make this decision an easy one!!
And you did it quickly!

Again all excellent responses and greatly appreciated. Advice graciously taken.

Thank you!

 

[sean9c]

These guys make a bunch of exhaust risers for Hino's, yours is probably a stock item for them
https://www.nationalmarineexhaust.com/

 

[jleonard]

I think $2300 to replace for both engines is cheap enough. Not worth chancing a home solution.

 

[Lepke]

Cast iron can be repaired if you can get to the crack and hole. It's not uncommon to repair new castings. A foundry or welding shop specializing in cast iron repair should be able to fix your castings.

 

[Comodave]

Diesel engines are great until you have to buy parts for them. I don’t think I would risk damaging a diesel by trying to jury rig the exhaust.

 

[Adequate]

Ordered new cast stainless risers. Thanks for all the replies. I'll feel better knowing its done correctly.
Now back to my laundry list of PM items!

 

[Comodave]

Ordered new cast stainless risers. Thanks for all the replies. I'll feel better knowing its done correctly.
Now back to my laundry list of PM items!

I think you did the correct thing. It hurts to spend the bucks but if it goes wrong you could spend many times as much. Keep us updated as to how it goes.

 

[Tiffany]

I had MESA make me a stainless steel replacement exhaust manifold for my Perkins T6-354 as I didn't trust the original cast iron manifolds - one never knows when corrosion will poke a hole through and even removing the manifold every 3 years to check is no guarantee of noticing an incipient failure. Given the peril of an engine rebuild I don't think marine manifolds are a place to skimp and save money.

 

[armando]

Forget fiberglass with high temp. You can use, only eventually, some pats existing in the market or even adhesives patch for temp that can rich 1000º C.
Perhaps you could also first cover the hole with a 1.5 mm stainless steel sheet.
There is no access for electric welding ??

 

[Adequate]

I ordered cast stainless thru North Harbor Marine. I'll post pics when they arrive.

 

[armando]

Yes Adequate, Best option !

 

[Adequate]

New, cast stainless risers arrived!!

 

[Comodave]

Boy, they are beautiful.

 

[rslifkin]

Those look like they should do the job for quite a while!

 

[ofer]

love it!

 

[Adequate]

Now then.......if I only had time to put them on!