Replace risers/manifolds?

Salt water, because of the way cast iron corrodes (peels off in chunks, first it starts to clog the riser passages and the risers start getting hotter than normal). One thing we salt water boaters do is use an IR heat gun to keep track of normal temps so when they start to rise you know that you have to start looking for problems. I have found my normal riser temps are 90-100 or so at idle (just warm to the touch) to 135 after coming off plane (hot but not burning hot to the hand). If I get temps higher than that I look first at raw water flow and then depending on how long they have been on, the exhaust system.
 
I replaced both of my salt water cooled motors last year. The port motor was a replacement that the previous owner installed after the original developed a rod knock.
The starboard motor was an original from 1987 that was always used in salt water and raw water cooled. I replaced it because it had low compression in a couple of cylinders. It just got tired. I did both of them while I was at it to start with two new motors, and because I was able to sell the good running port motor to a friend.
Anyway, after 25 years in salt water the motor that was original to the boat since 1987 amazingly enough did not have corrosion related issues. It had gone through several sets of manifolds and risers in it's life because of the salt water, but no problems in that regard to the motor itself.
I put half systems on the new motors when I installed them. I would have gone with full systems but held off because my Alpha drives would have needed the help of raw water pumps and the bilge is already to tight for me. Besides, while the full systems would have protected the manifolds, I still would have had to worry about the risers.
 
lots of good comments on riser replacement but I think he asked if it's worth it for engines with 1300 hrs. I'm sure others know alot more but I think that with modern engines and regular oil change, it's worth the change. How many hours does a well maintained engine get nowadays? They used to be shot at 1000 hours and cars at 100,000 miles, now it seems to be 2 or 3 times that.
 
quote:
Originally posted by GaryP

lots of good comments on riser replacement but I think he asked if it's worth it for engines with 1300 hrs. I'm sure others know alot more but I think that with modern engines and regular oil change, it's worth the change. How many hours does a well maintained engine get nowadays? They used to be shot at 1000 hours and cars at 100,000 miles, now it seems to be 2 or 3 times that.

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How long the motors are good for is real subjective. The best thing to do when on the fence is to start with a compression check. If that checks out and they seem to be running good and not using oil or running hotter than they should be then it is worth it.
 
I'm on my third set of manifolds and risers and will continue to change them as a maintenance item. Your engines will last a long time, how long who knows. Lots of speculation but the truth is too many factors to consider. If your concerned that your wasting money I can say your not. If the engines run good and you still like the boat you should do the manifolds and risers because if you don't the alternative isn't worth the risk. One quick example a buddy of mine had a 1988 Sundancer with original engines that had over 700 hours and who know how many sets of manifold and risers. He sold that boat last year and it was still running great.
Rob
 
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