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98 150 Vmax not pumping water in neutral except with earmuffs

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  • 98 150 Vmax not pumping water in neutral except with earmuffs

    So I recently bought this motor used along with a restored shallow sport. Boat is great but the motor has been nothing but trouble. First time I put it in the water there was nothing coming from the tell tale when I started it at the boat ramp. I take it back to him and he says he’ll have his mechanic look at it. An hour later he says it’s fixed. I go check it out and they have it hooked up to earmuffs and a hose and he shows me that it is pumping water.

    I get it back in the water... same thing. No water out of the tell tale. I realized later that when the mechanic showed me water coming out of the tell tale, he had it in Forward and was revving the motor a little. I’ve heard that some motors don’t put water out of the tell tale at low rpms except even though water is cooling the motor. So I get it moving a little and if I get it going to around 2k rpms+ then sure enough water starts coming out of the tell tale. But as soon as I slow down and put it in neutral, unless I shut the motor off right away, water stops coming out of the tell tale and then I get an alarm.

    So I figure the problem has something to do with the poppet valve. I go to check it out and find that the poppet valve is not there. The grommet is there but the spring and the valve itself are both missing. After installing one, I put the motor in water, start it up, and water is coming out of the motor fine, no alarms. But, as soon as I get above 2k rpms, the motor overheats.

    I take it back to the dealer, he says he’ll fix it. I figured there was probably damage to the impeller because of the overheating that had already been done, and when I got the boat back he said he had replaced both the impeller and housing because both were melted. There was also an oil leaker from the tank itself so they replaced that. Replaced the water pressure relief hose from where the poppet valve was because the hose that was there turned out to be the wrong part.

    I get it home, hook it up to the hose with earmuffs, starts up right away, sounds good, water comes out of the tell tale right away, no alarms, even after about 10 minutes. BUT, I notice some oil coming out of the back of the cowling. It’s not much and it is not black or anything. I thought maybe it was residual from the oil leak. So I wipe it away. Next day, I come back and there’s more oil dripping down again from the back. Not much, but it’s there.

    I wanted to see running it at idle was causing a leak or if it was still just a little more left from the oil leak before. Hook it up the the hose. This time it takes quite a lot to get it started, which was worrisome. Once started, it ran fine, no alarms. I decide to test it in the water. Put it in at the boat ramp, start it up... no water from the tell tale... overheats at idle. I also later noticed that water is leaking a bit from where the poppet valve is, and it wasn’t before. I have a sneaking suspicion that the mechanic removed it again.

    so that’s where I’m at.

    tl;dr - motor runs fine and stays cool with earmuffs on, but overheats at idle when sitting in water or moving at low rpms. Someone with a similar motor said it happened to him and it was the impeller. Supposedly new impeller already on, but I’m going to check on that right now. Anything else that might be the cause?

  • #2
    take the motor back to them to fix properly
    or get your money back.
    a motor that had a melted pump housing and impeller and PRV removed has more than likely been run hot and have other problems
    Last edited by 99yam40; 08-02-2020, 05:50 PM.

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    • #3
      I intend to take it back to him tomorrow, and I know he’ll work with me until it is fixed, or until he swaps motors out which he has offered to do if he can’t get this motor working right. I just want to know what would be causing this kind of an issue so I can give him good information.

      Checked the impeller and it does look brand new as does the housing, looks like it was installed correctly.

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      • #4
        Are there thermostats in the engine and if so, do they open?
        Last edited by TownsendsFJR1300; 08-02-2020, 07:25 PM.
        Scott
        1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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        • #5
          Thermostats look good

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          • #6
            Originally posted by Isle_of_Adrian View Post
            Thermostats look good
            looking good does not mean much

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            • #7
              In my experience with a variety of Yam 2 stroke HPs, they all piss like racehorses. This sounds like a water pressure issue, right?

              Garden hose/muffs delivers a higher water pressure vs submerged water pressure, which is why there is no issue when on muffs. When submerged the pump is either not generating enough flow of water through the cooling system (unlikely), or the pump is generating flow but it’s being obstructed. Have you tried clearing the water tube?
              Jason
              1998 S115TLRW + 1976 Aquasport 170

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              • #8
                So in taking apart the lower unit to inspect the impeller I thought “this looks really good, very clean. Almost too clean. So then I thought, I wonder if when they installed the impeller the didn’t apply any grease? Every tutorial I’ve ever seen or read of replacing an impeller has told me to apply grease inside the housing on the metal plates. So I made sure to put a good amount (not too much) before reassembling. Tested it again on the hose (mostly to make sure everything was reassembled correctly) and it worked fine. So then I put it in water at the boat ramp. Problem is gone. Pumps water fine in neutral at idle. No alarms. Little too late in the day to take it out and test it so that will need to wait until tomorrow?


                but could it really be that simple? This is the second impeller that this guy has put on... seemingly incorrectly both times. What other things should I check for?

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                • #9
                  Do NOT grease. I use glycerin impeller lube only !! Many impellers are sold in lil box with the no grease warning signs on them. With 40 years pro marine Tech.
                  I know what I'm telling you is 100 percent Correct. In the off season (winter) I have watched some YT marine repair vids in horror.. everyone thinks their are a mechanic.. not...Do not watch YT marine repair vids, if your smart.. that 727 your flying on today, do you want the mech/Tech watching YT jet repair vid's.. it's a NO brainer. Fact...if you own a boat there are repair costs.
                  Get used to it !! I sea 5/10 motors a year that are toast due to YT vid's or their. Brother is the a 35vet mechanic at ford, GM screwup motors. Myself I'm glad boating cost Sooo much !! What do you think the ramps and waterways would be like if boating was cheap. OUT



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                  • #10
                    Did you actually test the T-stats in hot water? PLz be honest here as to not waste time..


                    Plus one, ^^^, NO grease... I use a little liquid dish wash soap (Palmolive, etc) for assembly. Lubes then washes out quickly.



                    *And, you may want to follow, or at least look at the shop manual for certain procedures, WP's especially...



                    .

                    .
                    Last edited by TownsendsFJR1300; 08-03-2020, 08:11 AM.
                    Scott
                    1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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