riser function

[torcano]

What is the function of the risers? Do they carry sea water for cooling the engine or carry exhaust gases. I have a liitle water seepage at the junction of the riser the manifold. Does this mean I need a new gaskit or something more ominous? The engines are 4 year old 4.3L mercruisers with 190 hours in salt water.
Thanks

 

[Maclin]

Re: riser function

The risers are where the expelled cooling water meets the exhaust gases for expulsion thru the exhaust. They also "rise" above the waterline of the boat to act as a "trap" to aid in keeping water from travelling back up the exhaust.

I won't speculate on their condition, but seawater really works on these components and they will corrode much faster than they would in fresh water. Rust streaks on the outside usually mean at least the gasket needs attention, but it could also mean something as severe as the mating surfaces have thinned due to corrosion and the risers and/or manifolds need to be replaced.

 

[thedillybar]

Re: riser function

It's definitely worth looking into. The problem is that when they fail, water can get into the cylinders through the exhaust port (especially after the engine is shut off). Then you have the potential for all kinds of issues (rust on spark plug, piston, cylinder wall, head, valves; water in oil; starting troubles because it's hydrolocking).

 

[subcrx]

Re: riser function

always be up on those, they can cause many complications and costly

 

[Bondo]

Re: riser function

or something more ominous? The engines are 4 year old 4.3L mercruisers with 190 hours in salt water.

Ayuh,.... You're Due for total Replacement...

 

[chiefalen]

Re: riser function

Are you having any overheating condition? If not, and it's a small amount of water, ie: slow, slow drip.

Leave it alone till the winter and do it then. 4 years you should be within the window. 5 years tops on risers. If used in saltwater, and flushed with fresh water everytime you run in salt water.

If the boat stays in the water maybe you'll get 4 years.

Good luck!

 

[bomar76]

Re: riser function

Are you having any overheating condition? If not, and it's a small amount of water, ie: slow, slow drip.

Leave it alone till the winter and do it then. 4 years you should be within the window. 5 years tops on risers. If used in saltwater, and flushed with fresh water everytime you run in salt water.

If the boat stays in the water maybe you'll get 4 years.

Good luck!

The above is excellent advice IF you want to be buying new engines soon...

 

[torcano]

Re: riser function

Thanks for all the input. I just had the boat surveyed (just purchased) and that is how I found out about the slight weep of water on the riser/manifold junction. The engines are 4.3 L MPI Mercruisers. The engines were tested under load with computer which indicated good compression, no over heating and basically no fault messages as generated by the ECM. There is no visbile rust anywhere. The certified surveyor thought it could wait. Based on your comments, I plan to change out the risers and manifolds when I pull the boat out for the winter in 2 months. Based on the above, does anyone feel I should change these out immediately? Roughly, how much should I expect to pay to have a marina do this work. I have twin V6 mercs and I assume there are 2 risers and 2 manifolds per motor.

 

[Bondo]

Re: riser function

Based on the above, does anyone feel I should change these out immediately?

Ayuh,..... Tough Question,.......

Roll the Dice I guess.....

Your Surveyor actually Saw them,.... We're sitting somewhere, typing on the internet.....

 

[chiefalen]

Re: riser function

I wouldn't hazard a guess what you should be paying.

Most of us here do our own work.

Shop around for the parts if your doing it yourself.

If it were my boat i would wait for the winter.

You had a pro look at it. Thats what you paid him for professional advice. Smart move. Wasn't cheap that boat i bet.

Little bit of seepage ain't nothing. No overheating. Maybe you can try to gently tighten down the bolts on the riser gently.

Bye the way side point, those are good engines. Manually fuel injected. I lust for one of those in my next boat.

Good luck !

 

[chiefalen]

Re: riser function

Comment on what Bomar 76 posted. i usually let what he says or quotes me slip past. Guess he caught me at the right time. Here goes.

The guy has one little seep. Does that justify cutting off 1/3 or more of the summer laying the boat up in a marina till they can get to changing out the manifolds.

We all know with the summer in full swing the marina wont be able to get to him right away.

Parts have to be ordered.

And if everything goes as planned, they rarely do, a week when they take the first bolt off till he gets the boat back, maybe.

Twin motor engine. And only one seep on one riser. Could be snugged up the bolts a tad, maybe that fix is all he needs till the winter.

Hardly what i posted to the guy would suggest the slightest risk to his boat.

Never mind as you suggested, if he followed my advise both motors would be lost forever.

And he had a professional look at the motor where as we are posting miles away.

Bomar 76 have a nice night.

 

[torcano]

Re: riser function

Thanks Cheifalan. Actually, my surveyor suggested tightening the bolts on the risers. Can they be overtightened? I'm bringing the boat up from Point Pleasant to Red Bank in the morning. That should give me a good idea how she performs. I'll keep a close on the temperature guage and hope for the best.
RK

 

[chiefalen]

Re: riser function

I'm in manalapan. Spray some pb blaster or something like it on the bolts. Let it sit, maybe 10-15 minutes. Spray it again. Let it sit. Gently tighten them down.

1/2 turn would probably do it. Maybe do it after you run the motor. When its hot.

Gently now don't break off the bolts.

Good luck. I'll be on the water sat. in raritan bay. From keyport. I monitor channel 68 give me a shout. A few other friends will be on the water in there boats.

One guy testing his new engine. First time in the water.

 

[torcano]

Re: riser function

I'm usually out in Sandy Hook Bay. I'll give you shout on 68 if I make it up from Point ! By the way, what is pb blaster and where do I get it?

 

[chiefalen]

Re: riser function

i just went into the garage to look at the can.Liquid wrench blue can.Says on it loosens rusted bolts etc.

Wal-mart also get a can of corrosion pro. It's grease. Good to put on everything.

All the electrical connections and the motor itself. Keeps everything from rusting.

 

[torcano]

Re: riser function

Thanks. I'll look for you on the bay.