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Why does seagrass affect my motor but not others?


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I have a 2001 2200v with 2001 Yamaha carbed VMAX 150. I just returned from my second trip to Islamorada, first trip two years ago. On both of my trips the wind has blown hard out of the east, and there has been a TON of seagrass in the water. On my first trip, I got a temp alarm after idling through a no wake zone in a large creek where there was a good bit of grass in the water. I got towed back to the dock, flushed the motor and it never had another issue all week. On my second trip, I got another temp alarm after idling through the same exact creek - alarm sounded at almost the exact same spot in the creek, ironically. Again, I got towed back. Unfortunately on this trip, I did have another temp alarm after running about 2 miles in the ocean, again with a lot of grass in the water. This time I let it cool off, then ran back to the dock with no issues. The only thing I can think of that is causing my issue is the seagrass, my motor has never overheated anywhere else at anytime.

Why does the seagrass affect my motor and not those running the newer 4 strokes? Is there anything I can do to remedy this?

 

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Have you replaced your poppit valve?   The old valve is "T" shaped and would get stuck in that year model at low RPMs.   The new version is mushroom shaped and doesn't get stuck.  EASY replacement - I would start there.

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Im not making the connection why you think its seagrass causing it?  Kept waiting for you to mention you would find grass in the intake etc.  Given the age of that motor Id guess you have a good amount of scale buildup in the cooling passages and your symptoms do align with what youd start seeing once that scale gets bad enough or blocks some small holes that transfer water.  

Whens the last time the water pump was disassembled and inspected?  Thats where Id start... then test the thermostat to make sure its opening in the specd temp range.  Then move to the PCV- pressure control valve (aka poppit).  A stuck open PCV will cause low speed overheat stuck closed can blowout seals in the water pump and cause cooling issues, and what you find by looking at it and the cooling passage it resides in can provide a good indication what amount of scale buildup up it may have. 

 

 

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36 minutes ago, raymo said:

If you are referring to what is also known as an engine thermostat, yes. If there is another kind of poppit valve, would you mind elaborating?

 

Sorry, misspelled it - Poppet Valve - There are much smarter folks than me on here, but I have the same engine you have.   I was having the same issue, but for me, it was caused anytime I stirred up silt - which then got sucked into the cooling system.    The Poppet is a relief valve that redirects and maximizes water flow through the engine at lower RPM, then is pushed open at higher RPM when the flow is higher.   The original shape would get stuck at low RPM, which ultimately led to the overheat alarm going off.   Running the engine at a higher RPM for a short period of time would clear it, but it's a heck of a risk if you aren't sure exactly what's going on.   The original Poppet valve looked like the object in the upper left hand side of the pic below - note the "T" or "X" shape if you were looking at it head on.   That portion goes into the spring, the other side would go into the gasket and would get stuck.   The new versions basically cut off the portion that actually went into the rubber gasket and replaced it with a mushroom shape - which you can see in the video below.   It's a 5 minute fix, the part is cheap - I would start there.   The image below is actualy a merc version, but the link below is for the kit I believe you need:

https://www.ebay.com/itm/WSM-Yamaha-90-225-Hp-Poppet-Valve-Kit-785-200-/201606726101   

MERCURY 150-200 HP Poppet Valve Kit Replaces 803062T1 ...

 

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Very possible its just weeds, especially if it only happened one or twice in a week of running. Happens to four strokes as well. The times I've gotten an overheat alarm It was as simple as stopping, bump it in reverse or shut off the motor and trim it up to clear the weeds. Many times stopping will cause enough turbulence to dislodge the weeds. Restart the motor and run it as normal. As long as the alarm stops, no need to let it cooI and definitely doesn't require a tow. As long as your water pump is good and you have water flow, it'll return to normal operating temperature quickly after the weeds are cleared. If you have repeated alarms and no obvious signs of clogging by weeds then you have another problem.

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2 hours ago, FINCHASER said:

Im not making the connection why you think its seagrass causing it?  Kept waiting for you to mention you would find grass in the intake etc.  Given the age of that motor Id guess you have a good amount of scale buildup in the cooling passages and your symptoms do align with what youd start seeing once that scale gets bad enough or blocks some small holes that transfer water.  

Whens the last time the water pump was disassembled and inspected?  Thats where Id start... then test the thermostat to make sure its opening in the specd temp range.  Then move to the PCV- pressure control valve (aka poppit).  A stuck open PCV will cause low speed overheat stuck closed can blowout seals in the water pump and cause cooling issues, and what you find by looking at it and the cooling passage it resides in can provide a good indication what amount of scale buildup up it may have. 

 

 

My guess is that while running, the grass would collect and create blockage or prevent or reduce water pickup and cause it to overheat. When I heard the alarm, I stopped. I was never able to actually see the blockages...my guess is that upon stopping, they fell out of the way due to no suction, etc. 

The motor is 20 years old and has been in used in saltwater primarily in its life...Ive only owned for 5 years and flush it regularly. I KNOW there is scale, but I have never had a problem anywhere else, anytime. The motor is serviced annually even though I put maybe 40 hours per year on it. A full waterpump kit was just installed prior to leaving this trip. Thermostats replaced in 2019, after the first trip...as a suspected cause. Again, no problems anywhere else, including the week before putting in for service before leaving for the trip.

Thank you for the lead on the PCV valve and your insight...Im going to make sure that is new.

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I just came back from a month on Big Pine Key.  There was a lot of grass in the water.  I just kept an eye on my water pressure gauge.  Every time the pressure would drop, I would put the engine in reverse and my water pressure would immediately go back to normal.

My water temp alarm never went off.

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On my Maverick with an F70, it got grass-wrapped all the time. As others have done, I’d watch the water pressure gauge if I thought I picked up grass. If it dropped to zero, I’d stop, put it in reverse to lose the grass, and then take off. While much better than waiting for the alarm to go off and sitting till it cooled, it’s still very inconvenient when there’s a lot of grass around.  This year I installed a new low water pickup system developed by a friend of mine and I no longer have any grass problems. 
 

My Pathfinder has a 250 SHO, and with its nose cone pickup, I never have any grass problems. 

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17 hours ago, wthree3 said:

Very possible its just weeds, especially if it only happened one or twice in a week of running. Happens to four strokes as well. The times I've gotten an overheat alarm It was as simple as stopping, bump it in reverse or shut off the motor and trim it up to clear the weeds. Many times stopping will cause enough turbulence to dislodge the weeds. Restart the motor and run it as normal. As long as the alarm stops, no need to let it cooI and definitely doesn't require a tow. As long as your water pump is good and you have water flow, it'll return to normal operating temperature quickly after the weeds are cleared. If you have repeated alarms and no obvious signs of clogging by weeds then you have another problem.

Exactly. Have done this several times over the years when running in sea grass. FYI, vmax hpdi’s do not like running at idle for a long time. Do not know about the carbed ones. They tend to overheat. Never had it but been told. 

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I had the same engine. Regardless of having new water pump, T stats and Poppet valves it just never had good water pressure. Could be scale build up as mentioned above. I had to change my impeller and water pump yearly to keep pressure up. Anything that blocks the intake or passages makes it even worse and will give the over heat alarm. 

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18 hours ago, raymo said:

My guess is that while running, the grass would collect and create blockage or prevent or reduce water pickup and cause it to overheat. When I heard the alarm, I stopped. I was never able to actually see the blockages...my guess is that upon stopping, they fell out of the way due to no suction, etc. 

The motor is 20 years old and has been in used in saltwater primarily in its life...Ive only owned for 5 years and flush it regularly. I KNOW there is scale, but I have never had a problem anywhere else, anytime. The motor is serviced annually even though I put maybe 40 hours per year on it. A full waterpump kit was just installed prior to leaving this trip. Thermostats replaced in 2019, after the first trip...as a suspected cause. Again, no problems anywhere else, including the week before putting in for service before leaving for the trip.

Thank you for the lead on the PCV valve and your insight...Im going to make sure that is new.

Pics (before and after) of the amount of scale buildup below of a yamaha pro V 115 at 14 years old I cant believe it was cooling at all.   I was getting the occasional temp alarm as well.  Never had one again for the other 6 years I owned it after cleaning it and could readily see the difference in water flow by the tell tale.... after cleaning water came out at much higher pressure.  

Itd be worth testing the thermo switches too to make sure they are operating within temp.... they are the actual temp sensor that trigger the alarm.  Its possible 1 could be triggering an alarm at a lower temp than it should. 

 

100_0485.JPG

100_0492.JPG

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I had a 150 VMAX 1997carbed which lasted for 20yrs,but finally had a corrosion leak in the water jacket.  It is too bad those earlier 2 strokes didn't have flushing ports .  If you didn't flush after every use it would end up with an issue.  I would get rare over heating from grass collecting on the lower unit but it be fine when I stopped and remove the impediment. I will add that I had a slip for the boat,and wasn't able to  run the motor on Muffs.

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On 6/12/2021 at 6:15 AM, polliwog said:

It is too bad those earlier 2 strokes didn't have flushing ports

Yup! My 1998 Pro V 175 doesn't have one ether.  I keep my boat in the water for days at a time in the keys and other areas several times a year.  It really *** that i cant flush it after every days use.  

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