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    Riser Temp-gctid381373

    My port risers seems to be running hotter, is there a temperature spec? Mine are raw water cooled.
    Partner in a 1999 4788

    Seattle, WA

    #2
    One side always runs hotter. Just the nature of the beast.
    Be good, be happy, for tomorrow is promised to no man !

    1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

    '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

    Manalapan N.J

    Comment


      #3
      I've ordered an IR thermometer, and will later post the temps
      Partner in a 1999 4788

      Seattle, WA

      Comment


        #4
        When one side runs substantially hotter than the other, it can usually be traced to an unqual division of the spent sea water.

        This could be at the T-stat housing outlets....., it could be with a diverter T (closed cooling system)......, or fittings that are restricting flow to one side......, or even the manifold-to-riser transfer ports being rusted and restrictive.

        Some temperature differential is expected and acceptible.... but excessive is not good.

        .
        Rick E. Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

        Comment


          #5
          It seems excessive and different, but I can't be sure. I have a 1/2 FWC system on an Alpha Gen 2. The block is freshwater cooled and the manifolds/risers are raw water cooled. The pump in the leg is working fine, a two hour cruise at 3700 rpm. Had the engine temp running at normal. I am not sure how the water is split in these systems after it leaves the heat exchanger. Maybe I just need to start removing hoses and see what's clear.
          Partner in a 1999 4788

          Seattle, WA

          Comment


            #6
            I recommend putting your boat's details/specs in your signature. That way, people will know what you have right off the bat in future posts. Considering you own a Merc Alpha 1 Gen II, it's actually fairly common for there to be a noticeable temp difference between the manifolds/risers, and then for no apparent reason, it will switch sides. However, if yours is always and consistently running hotter on one side, then it would be time to start disassembling things. At a minimum, remove the hoses to check for blockages (including the side that's running cooler so you have a baseline for comparison). It would also be worth your time to remove the riser (again, both sides preferred), particularly if you don't know when/if they've last been inspected. Freshwater is typically much kinder on the manifolds/risers in terms of rust, but there are always exceptions. Riser/manifold gaskets are pretty cheap, and it's fairly easy to do. This will also give you an opportunity to check the insides of the large rubber exhaust coupler hoses, and you can check the the exhaust flappers further downstream from the couplers.

            Comment


              #7
              guna be real honest. I have put many hours and a long post into this issue. 1 riser on my old 2355 was hot to the touch, coudlnt keep your hand on it for long, one was cool and you could all day. This was normal operation for my engine, newer ones installed a ball valve to equalize the water flow better. AN IR gun confirmed that the temps were well within acceptable limits.

              Comment


                #8
                stargazerwa wrote:
                It seems excessive and different, but I can't be sure. I have a 1/2 FWC system on an Alpha Gen 2. The block is freshwater cooled and the manifolds/risers are raw water cooled. The pump in the leg is working fine, a two hour cruise at 3700 rpm. Had the engine temp running at normal. I am not sure how the water is split in these systems after it leaves the heat exchanger. Maybe I just need to start removing hoses and see what's clear.
                This depends on your system.

                Some are divided right out of the H/E via two separate outlet ports.

                Some H/E's have a single outlet that leads to a splitter "T" or "Y" looking affair.

                One outlet becomes two.... one Port... one Stbd.

                This "T" or "Y" fitting will have a copper divider down the center just prior to the split.

                If this divider is not centered (in terms of flow division) you may see unequal water flow which leads to unequal manifold temperatures.

                One of our premeir Closed Cooling System manufacturers had an issue with these several years ago. The fix was a new splitter fitting.

                I fully disagree that substantially unequal temperatures are acceptable.

                .
                Rick E. Gresham, Oregon
                2850 Bounty Sedan Flybridge model
                Twin 280 HP 5.7's w/ Closed Cooling
                Volvo Penta DuoProp Drives
                Kohler 4 CZ Gen Set

                Comment


                  #9
                  This topic comes up every year about this time. Most people complain about this phenomenon when running on the muffs.

                  It is normal to have a temperature differential from one riser to the other. If you can keep your hand on it without burning yourself, it is fine. You may even see the hot riser change to the opposite site from time to time.

                  Taking an IR thermometer to the engine room is just going to send you into mind-fcuk mode. Mercury Marine has never released any sort of maximum/minimum riser temperatures in their engineering data. I've talked to technicians at Mercury at great length about this issue and their official guidance is that if you can touch it, it is fine. You are basically touching the engines muffler with water running through it. It is expected that it would be hot in this area. Put your tongue on your cars muffler ... tell me if it's hot.

                  If an engine or risers are getting too hot, the first thing you will notice is the smell as the flappers start to melt. If you don't smell anything unusual, then all is well.
                  Mocoondo
                  2002 Bayliner 195 Capri
                  Mercruiser 5.0L V8 / Alpha I Gen II
                  MMSI: 338091755

                  Comment


                    #10
                    The original post stated raw water cooled nothing about a split system. If your engine never gets above 180 then your in like Flint.

                    Now here's how i look at it 5 years tops on risers / elbows if you boat in salt water. NO MATTER WHAT ONE SIDE WILL ALWAYS RUN HOTTER THEN THE OTHER PERIOD !

                    Maybe one riser is telling you it's time for a new one.

                    You should know when the risers where changed last... if not pull them off and have a look see.

                    I'm not trying to pick a fight here with anyone but this ain't new chit here in this thread.
                    Be good, be happy, for tomorrow is promised to no man !

                    1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

                    '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

                    Manalapan N.J

                    Comment


                      #11
                      As I said in my original post the manifolds/ risers are raw water cooled, this is because it is a split system. These are pretty common with Alpha's. I didnt want to start an argument, but I do appreciate the feedback. My mechanic told me to keep an eye on it as the port side was hot on the muffs. I put it in the water, started it up and it was ok. Ran it about an hour away and back and tied up to the dock and the port was fairly hot the starboard was only warm.

                      It sounds like it may be fine, but I will check the hoses first and take some temps, I have been wanting an IR thermometer anyway. Thanks again for the help everyone.
                      Partner in a 1999 4788

                      Seattle, WA

                      Comment


                        #12
                        Optimus wrote:
                        I recommend putting your boat's details/specs in your signature.
                        Ditto!

                        Mocoondo wrote:
                        This topic comes up every year about this time. Most people complain about this phenomenon when running on the muffs.

                        It is normal to have a temperature differential from one riser to the other. If you can keep your hand on it without burning yourself, it is fine. You may even see the hot riser change to the opposite site from time to time.

                        I've talked to technicians at Mercury at great length about this issue and their official guidance is that if you can touch it, it is fine.

                        If an engine or risers are getting too hot, the first thing you will notice is the smell as the flappers start to melt. If you don't smell anything unusual, then all is well.
                        Bingo! Key words "Too Hot".

                        Chief Alen wrote:
                        The original post stated raw water cooled nothing about a split system.

                        [COLOR]"#0000FF" wrote:
                        Chief, the OP did mention this, and I responded to in post #8. [/COLOR]

                        stargazerwa wrote:
                        I have a 1/2 FWC system on an Alpha Gen 2.
                        If your engine never gets above 180 then your in like Flint.

                        [COLOR]"#0000FF" wrote:
                        Engine temperature/riser temperature....... Apples/Oranges in this conversation... yes/no? [/COLOR]

                        NO MATTER WHAT ONE SIDE WILL ALWAYS RUN HOTTER THEN THE OTHER PERIOD !

                        [COLOR]"#0000FF" wrote:
                        Define; ALWAYS RUN HOTTER THEN THE OTHER.... as in just how much hotter!

                        As I have suggested, substantially hotter would not be OK. Mildly warmer, would be acceptable, IMO. [/COLOR]

                        Maybe one riser is telling you it's time for a new one.

                        [COLOR]"#0000FF" wrote:
                        Yes, that or time for looking at the transfer ports.[/COLOR]
                        stargazerwa wrote:
                        • 1 wrote:
                        • As I said in my original post the manifolds/ risers are raw water cooled, this is because it is a split system. These are pretty common with Alpha's.
                        • I didnt want to start an argument, but I do appreciate the feedback.
                        • My mechanic told me to keep an eye on it as the port side was hot on the muffs. I put it in the water, started it up and it was ok.
                        • Ran it about an hour away and back and tied up to the dock and the port was fairly hot the starboard was only warm.
                        • It sounds like it may be fine, but I will check the hoses first and take some temps, I have been wanting an IR thermometer anyway. Thanks again for the help everyone.



                        • 1 wrote:
                        • Yep!
                        • No arguement caused by you.
                        • Running with the muffs will not create the same scenario as if actually being in the water.
                        • IMO, your more important check will be while running above low speeds.

                          If the risers are much closer to being the same temperature while above low speed, you are very likely OK.

                          When you get things sorted out, you'll likely find them to be close even at low speed.
                        • Yes.... just follow the path of the spent cooling water, and it will lead you to the problem area.



                        Rick E. Gresham, Oregon
                        2850 Bounty Sedan Flybridge model
                        Twin 280 HP 5.7's w/ Closed Cooling
                        Volvo Penta DuoProp Drives
                        Kohler 4 CZ Gen Set

                        Comment


                          #13
                          Well, my manifolds and risers are shot. Headed out yesterday and everything was fine, port riser was defiantly hotter, but I could touch it. After running through Deception Pass we got a whiff of a hot smell we pulled into Bowman Bay and were fortunate to find dock space on the dock in then Northern cove (Sharps Cove??). I checked out all the plumbing and everything was open. Port riser and manifold was hotter then h%#Ôé¼. Pushed a long wood screw up through the drain plug hole and it came out a decent amount of rust, but nothing too shocking. If I blew through the port hose, it was somewhat restricted compared to the Starboard. Decided there was nothing else to do there. I did take a vise grip and arrange a moderate amount of flow restriction on the Starboard side. We decided to run back via Anacortes, more marinas to duck into or be towed to. After about 3nm the engine temp was rising hotter than normal ~200 according to the gage but still rising so I took the vice grip off. We ran another couple of miles and the hot smell returned. Shut it down and bobbed around in Guemes Channel just off of ships harbor looking for a place to take it. Made an arrangement with Cap Sante Marine. I put the vise grip back on and made it there before the engine temps got to hot. Had my oldest come pick us up so could get back to LaConner.

                          Until we had the hot smell I could always touch the port riser. My EBay IR thermometer has not arrived yet so I don't know the actual temps. If I learned anything from this it is I should have trusted my instincts when I though something had changed.

                          It's an interesting system, there is no waste gate or any thing to adjust the flow, just gravity, in fact the way it's plumbed the port site would probably get a bit more flow. Thanks everyone for the help.
                          Partner in a 1999 4788

                          Seattle, WA

                          Comment


                            #14
                            FWIW and FYI: Try your best to never restrict one side to compensate for a higher temperature at the other side.

                            Instead, try to open up the side that is running warmer.

                            As designed, the system will be balanced well enough when all ports are clear and free.

                            .
                            Rick E. Gresham, Oregon
                            2850 Bounty Sedan Flybridge model
                            Twin 280 HP 5.7's w/ Closed Cooling
                            Volvo Penta DuoProp Drives
                            Kohler 4 CZ Gen Set

                            Comment


                              #15
                              I am unsure what FWIW means, but the constriction was an attempt to get use back to a port without a tow. But I agree it wasn't designed that way!
                              Partner in a 1999 4788

                              Seattle, WA

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