Replaced exhaust risers

[tonyiiiafl]

Replaced my 6 year old risers on the 454’s. Truly still in good shape. Had some corrosion on the throat of one of the manifolds. However, riser edges are SHARP! First riser I did this. Made it through the next 3, but it was hurting like you know what. Thank the high heavens for paper towels and electrical tape!

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[Viper]

OUCH. Been there done that!

Good job Tony. Aren't boats fun?

[tonyiiiafl]

Love every minute I if it. Took me an hour each side. Marina quotes 6 hours. And that did not include clean up. So I saved $1200.00 for just the cost of a little discomfort and a lot of satisfaction.

[paulr]

I also have the job coming uo. What engines do you have? Did you mean you changed the risers and elbowws or just the risers?

[dgreene]

Thanks for the post. This is on my to do list as well. Never done it before, so I’ve been dreading it. I’ll try to remember the mechanics gloves when handling the sharp edges.

[tonyiiiafl]

I have 454’s. Elbows are same as risers on my engines. Just remember to drain the coolant down if you have closed cooling

[tonyiiiafl]

Ran my engines again today. Port is A OK. However, starboard seems to get up to 120 and stay around there. I may have not ran it long enough. I shut it down and started and it went up to temp. All I did was replace the risers. Risers and manifolds do get warm/ Wondering if perhaps an air bubble? is that brass plug on the thermostat housing a bleed plug? We did run it when done, same thing. Checked and added some coolant after thermostat opened.

With closed cooling, what do you all run for thermostats? 160? With 160 it gets up to around 170 or so, 185 when running it hard.

Thank you!

Tony

[km1125]

If the temperature varies much from the thermostat then you have some kind of lack of flow going on, usually in the raw water side. Could be a restriction prior to the raw water pump, an impeller or cam issue in the pump, or a restriction further downline. I would never expect it to get more than 10F over the thermostat, but even then I'd be wondering why it's that high. It's not a **problem** until you get closer to 200F but there could be some hot spots in the engine that won't like running that high. Plus, the higher temps on the fresh side mean that more solids are going to come out of solution on the raw side and cause more "plugging" up of parts (heat exchangers, oil coolers, manifolds (for half systems) risers and elbows). It also means your oil temp is going to be higher which should trigger shorter oil change intervals.

160F is pretty common in closed cooling. Some can run higher temps, but note that if you run higher than the engine was designed you may have to adjust things like spark timing to compensate.

[tonyiiiafl]

I drained the coolant down and funny the heat exchanger did not go down. Has anyone opened that plug on top of the thermostat housing to bleed air out? Once it got to temp you could see the gauge hut temp and drop back. Repeat

[bud37]

Considering you drained the coolant down you may have some small air pockets.....they will be absorbed over time by the trapped coolant, so just keep checking levels.

Now in my experience engines that get quite a lot hotter when just run mildly hard are having a problem with heat exchanger efficiency. Because you are seeing salt you have to keep the temps down in the exchanger as mentioned or the salt/minerals will separate and adhere to the exchanger surfaces thereby making things worse and the spiral starts. Perhaps it is time for a flush......

Actually the warmer you can run an engine within reason the more efficient the heads will be, but with marine engines there is a caveat if you boat in salt/brackish water. .....my opinion anyway.