260hp Mercruiser blowing exhust hoses

[searaybill]

I own a 1985 Searay Sedan Bridge with twin 260hp mercruiser engines. As far as I know(I bought it used) they are the original engines. They both run very well and have good compression. Recently the port engine has been blowing a hole in the exhuast hose that runs from the riser to the muffler. It has done this twice in the last 3 months or so. The hole is always in the same spot, on the top side of the hose and just after the neck on the riser. They both run at around 145 degrees, so they don't seem to be running hot. Yesterday I was out and I notice the engine wouldn't idle very well, as a matter of fact it stalled out twice. If I bring them up to cruising speed the port engine will top out at about 2500rpm and run very rough. After a few minutes it begins to smooth out and then ran normal. Once I got to my destination, I checked and found the exhaust hose with a hole in it. To get home, I used duck tape on the hose and took it real slow(never over 2300rpm). Engine ran fine, but I need to know what the cause of these hoses blowing out is. The engines always start with no problem. A friend of mine who is mechanically inclined thinks that it might be the riser and or the manifolds. Any suggestions?<br />I appreciate any help you can give.

 

[BRIAN03]

Re: 260hp Mercruiser blowing exhust hoses

The exhaust water tempure is too high. You burn't a hole in the exhaust hose. You either have a flow problem from the raw water pump or the exhaust risers are clogged. With the age of that boat it needs new risers and new exhaust manifolds. I would also inspect the water pump impeller and thermostate. Rises every 6 years and manifolds every 8 years. Impeller and thermo every other year.

 

[johnkc]

Re: 260hp Mercruiser blowing exhust hoses

make sure that the exhaust hose goes straight off the riser ,that it is not taking a downward bend too soon off the riser .

 

[MFG197]

Re: 260hp Mercruiser blowing exhust hoses

in my merc install manual there is a section about that. the hose needs to come straight off the riser to avoid a spot on the inside of the hose where hot gasses collect with no water, this will burn a hole in the hose. If you want I can scan and email to you.<br /><br />mfglmg@sbcglobal.net

 

[searaybill]

Re: 260hp Mercruiser blowing exhust hoses

Thanks to everyone who replied to my question so quickly. I have been thinking about replacing the risers and exhaust manifolds, so I guess this it's time to bite the small bullet before I have to bite the big bullet. To WWYCna7, I would greatly appreciate it if you could scan that info and send it to me. I believe that this is very important because the last time I replaced that hose I also replaced the hose going to the muffler and noticed it was sitting a little lower, which would make the hose off the riser turn down a little faster than the one on the starboard engine.<br /> One other thing that was mentioned was the thermostat. I replced it on this engine about 3 months ago and since then this engine comes up to 145 degrees much faste than the starboard engine. the starboard engine will stay around 130 degrees until I get up to cruising speed. Which is right the port or the starboard. Once again thanks for your help everyone

 

[jam39vw995]

Re: 260hp Mercruiser blowing exhust hoses

Starboard is the right side when facing the front of the boat.<br /><br />An easy way to remember which is port and starboard is this.<br /><br />Port is a 4 letter word. It's the left side, left is also a 4 letter word. That's how I remembered it when I first learned about boats.<br /><br />Good luck on your search for a solution to your hose problem.

 

[MFG197]

Re: 260hp Mercruiser blowing exhust hoses

searaybill: I have the page scanned email me with your address: mfglmg@sbcglobal.net