Still overheating

[Ray Ritchotte]

Well I did every thing that I can think of. I changed the impeller and installed a new water pump housing (performed at a boat shop). Went on the lake and the motor overheat horn came on as soon as I throttled up to 4700 RPM's.
Came home and removed the water pressure control valve (Poppit) and its clean as new. new rust, no debris, and the spring is good. The next tthing was to pull the thermostats and replaced them with new ones gaskets etc.
The old ones looked like S$$$t so I installed new ones.
Just for the heck of it I took the old ones and heated a pan of water to 125 degees which is 50 degrees celcius on the thermostats and guess what ?? they both opened at 125. I don't know what to do next. I'm going to go back on the water on Wednesday to see if the damn thing overheats again. Guys I'm lost for words any help will do.
Yamaha Pro V 150 tlrp. 1991
Thanks ray

[Ray Ritchotte]

I forgot to add that my water pressure is 20 to 25 psi and just before it overheats it drops to 15 psi ????

[Ray Ritchotte]

Overheat alarm

Come on guys I desperately need some help!!!!

[99yam40]

Are you sure it is overheating? could it be oil level?
Seems strange that as soon as you hit 4700 the alarm goes off.
Will it run without alarming at a lower RPM?
and does the water pressure stay up at the lower RPM?
In my opinion If the pressure drops it must be sucking air or exhaust from some where

[Ray Ritchotte]

Thanks for answering. Yes it is overheating because the alarm is a straight horn and not a beeping horn plus the overheat temp symbol comes on and stays on until motor cools down. I have a the bar graph trim indicater and it seems like when I trim up to between 3 and 4 the motor will overheat. Water pressure at that time goes from 25 psi to 15 psi and then a few minutes later the horn and indicater comes on. The boat doesn't reach plane yet also. It seems to only do this when i start going to WOT from around 3500 rpm's to somewhere at 4500 rpms. Water pressure drops to 15 psi when this happens.
Two years ago i use to be able to trim motor up to 4 on the anolog bar on the trim gauge/rpm gauge. I have the type of gauges that show speed/trip/fuel/water temp symbel/low fuel sumbol/and charge symbol on the left gauge and the right gauge shows rpm/trim/low/med /full oil gauge all computer type gauges
Is there any way I can flush this moter by taking out the thermostats and poppit valve and run water thru the motor ??

[bassinflats]

overheating

I have the same problem 1993 pro-v have had the water jackets bead blasted twice, power head removed and water jackets cleaned, water pump, thermostats and popet valve replaced and yesterday checked thermoswitches. Last time ran good for about 4 mos now same problem, can run all day at 4300rpm but when I go to 4500 rpm for 4-5 min will get buzzer and drop down of rpm leave it idle for a couple of minutes and take back off again and my water indicator flashes when I get buzzer. Really don't know what else to do. One mechanic I talked to wants to bead blast ater jackets again. Last time had pwer head removed it cost me 900 dollors and worked good for about 4 mos and I only run freash water. Thought maybe it was because water twmp has has been so warm here in Fl, but water has cooled down and it still happens.

[Ray Ritchotte]

Is there any tech's out there that can help both of us ?????

[99yam40]

Thanks for answering. Yes it is overheating because the alarm is a straight horn and not a beeping horn

That shows you what I know, I always thought there was only one kind of alarm, a steady horn.

it seems like when I trim up to between 3 and 4 the motor will overheat. Water pressure at that time goes from 25 psi to 15 psi and then a few minutes later the horn and indicater comes on.

Sounds to me like you are getting the motor up too high and sucking air


The boat doesn't reach plane yet also.

Seems like the boat should be on plane in a few seconds not minutes.
You may have other problems

It seems to only do this when i start going to WOT from around 3500 rpm's to somewhere at 4500 rpms. Water pressure drops to 15 psi when this happens.
Two years ago i use to be able to trim motor up to 4 on the anolog bar on the trim gauge/rpm gauge. I have the type of gauges that show speed/trip/fuel/water temp symbel/low fuel sumbol/and charge symbol on the left gauge and the right gauge shows rpm/trim/low/med /full oil gauge all computer type gauges.

Maybe the trim indicator has moved or is out of adjustment and you are trimming up to high now

[Ray Ritchotte]

I tried it with the trim only on the 2 bar and the boat plowing water. As soon as I reach 4300 rpm's after about 2 minutes the alarm goes off. Still peeing good and psi is 15 - 18 lbs showing.
Someone suggested to get new water intakes. Seems like I read somewhere that Yamaha had changed them.

[mrv8outboard]

well I just replied to your other post for the same thing and found this one which had some more info. Check the temp of the engine with a non contact temp probe. Like a point and shoot inferred. Verify it is overheating. Do this ,do not skip. If it is then look at the bottom and transom of the boat. If you are sure it is OK (post pics if you are not sure) then I would suggest the upper water tube grommet is restricting water flow.

Now if you find it is not really overheating now what?



Check the charging system. Yes you can do that first but will distract you from the real issue so do not be concerned with this unless you do the above steps and find your self here. We can go into it then.

I believe it is something on the bottom/transom or the water tube grommet.
Let me know.