EH700 Exhaust Risers-gctid390789

[Guest]

Hello All,

I'm trying to determine if its time to replace my risers. I've ordered some oil samples to look for sodium content as i'm starting to see a little bit of corrosion and calcium build up around the elbows. Does anyone know if the after market cast risers are date stamped? I do see what looks to be a date stamp indicating 03 28 01 but not sure if its the date or a cast number. The previous owner is no longer around to ask.

Thanks

[mmichellich]

Doesn't really matter how old they are, but how far blocked are they. You have to remove the exhaust hose and see the percentage of blockage in the riser by looking. How much of the outer wall is remaining? You will see a lot of rust and scale, how much of original exhaust area is still open. Do the exhaust risers still allow adequate water flow out the exhaust? Do the engines over heat at fast cruise speeds? Is the water coming out of the exhaust hot or just luke warm, like a little too cold to bathe in. Are you getting black smoke when engines are loaded, which can come from excess back pressure? I have seen risers on Hinos shot after 4 years and others are 20 years old and still in usable shape. If they look OK, you might want to carry a spare riser and a spare exhaust hose, I do.

[Guest]

I have a 5.7 twin gas 34 foot Bayliner. I just replaced the 4 manifolds/risers with cast iron ones from Sierra. The old manifolds/risers were 10 years old and had been exclusively in salt water. I found that the old ones still looked quite good with little scaling or other signs of wear. However I am not sure how you ever know what the internals of a manifold/riser look like. So much of the water jacket is out of view. Also, once you go through the large effort in a small space to remove them it seems prudent to replace. I do fresh water flush after almost every use and maybe that helped keep them in good shape.

I talked with and viewed the web sites of all the major suppliers. They are quite willing to give advise over the phone. Barr, Sierra, PFP, Mercruiser, etc. The folks at PFP were very helpful. Also a local Seattle shop, Fisheries Supply was helpful.

The mechanic sold me on Sierra since in his opinion they are large enough to have the resources to replace them if a defective one comes along. Most castings are poured in China but I think Barr makes their own.

I went into this project liking aluminum for the light weight and corrosion resistance. However several of the suppliers recommended Cast Iron even though they sold aluminum unless you are a high performance go fast boat and want the lighter weight. Aluminum has its own set of issues regarding zincs and errosion. Some companies said they are no longer offering coatings. I looked at stainless but decided it was price prohibitive unless you plan on keeping the boat forever.

I also decided to keep the fresh water flushing routine and will use a infared thermometer to track temp at various places on the manifolds as the years go by.

Hope this helps. I did also discover that several stores have very different prices for the hardware.

Good luck,

Russ

[Guest]

I though mine were in good shape; they were, however, original. Earl pulled them off three years ago and replaced them with ceramic coated ones. My originals were trashed. Mostly blocked and rusted out yet the boat performed well and I had no external indications. If you actually see rust and salt build up I'd be at least pulling them off to have a look.

[Guest]

Thanks guys, The engines have never given me an ounce of worry. Tempuratures are always solid at high and low speed cruising. Haden't thought to check the water tempurature coming out of the exhaust though. Just be be sure I've ordered up an oil analysis to check for high levels of sodium. Either way I think its time to pull them off and have a look. I've done most of the maintainance myself over the years but haven't tackled the risers and elbows, Is there any tricks to the job?

[tweekes]

When I bought my 3870 ten years ago, there was a beginning of rust coming from where the riser bolts on the the manicooler which was a giveaway. I pulled the hoses and they were pretty ugly with much of the water jacket blocked but I had no temp issues. I replaced them with stainless can type risers and they have performed just fine with no pinholes or weld issues. I got them from somewhere in the NW, Marysville? It's been too long ago. The guy who builds them is or has been on the forumm.