Offshoreonly.com - 496HO riser is blistered

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- - 496HO riser is blistered - Overheated? (https://www.offshoreonly.com/forums/sonic/266452-496ho-riser-blistered-overheated.html)

Quote:

Originally Posted by myturn (Post 3697600)

Attached are a couple of shots I took of my
riser problem last fall. The problem was
hose clamps that Mercury uses. One of them
corroded and popped of while I was running.
No alarm just a fire and smoke coming from
the engine compartment. All cooling water to
the riser went into the bilge so the riser quickly
over heated! I shut the engine down and the
fire stopped. What a mess. It took me four
hours to idle home on one engine. One thing
to Mercury's credit is that the closed cooling
system protected the engine from any damage.

Ouch! That looks like it could have been worse than it was. Lucky for mine as I just got up on plane I heard a loud pop and the motor sounded like something blew which was the hole in the top of the exhaust hose. All clamps were in place. I immediatlehy shut her down. I took it to a diffferent mechanic today who I have used in the past. Lets see what they come up with. I am definitely staying away from the new place I used over the winter. Never going back there again!

If they replaced the impeller, the first thing that needs to be done is get the impeller chunks out of the fuel and oil coolers. The chunks restrict water flow even with a new pump impeller. I had one go bad on my old Scarab and the first thing I did was pull the oil cooler. Yes they were there. Lesson learned!

Ed

I had been overheating on my old 454 even after rebuilding the sea water pump and ensuring the seawater strainer was clean.

I found sand and rust in both of my risers. I used a long screwdriver to clean out the water passages with the risers removed. Now running at normal temps no mater what throttle setting.

Quote:

Originally Posted by U4ICK (Post 3698875)

My impeller, luckily enough, did not blow out any chunks and was worn along with the brass water pump being scored, so I dont think anything got caught in there. Appreciate your feed back. :O)

I had the hose replaced with a stronger one, I went out again this past Sunday and the darn thing blew another hole in it. Comes to find out, the tech contacted Merc after I brought her back in again to adress the issue and Mercruiser said the hose has to be properly installed at a correct angle, so the exhaust heat is not blowing directly on exhaust hose. The direct heat is causing the hose to fail on top just after the riser opening. So, they got the info from merc how to ensure it is on correct and the shop is going to take her out for a test to see if that works. I'll keep ya'll posted! ulg! Also to note... I had the shop back flush the motor this time and nothing came out.

Quote:

Originally Posted by 26sonicmotion (Post 3708660)

Problem solved! Merc was correct and the exhaust hose is now installed correctly and there are no issues! She is running 100%