Over Heating Yammie 1992 150 2stroker.

[willy]

Went down today and did some work on my V, changed filters etc. was going to go out, it was on a work station and I was running the motor on muffs, started fine as normal, after running for about ten minutes all of a sudden the overheat alarm sounded, I checked quick and the hose was going good, the pisser was pissiing so I shut her down and started checking. Pulled the cover off and felt the engine by the T stats and could not keep my hand on the heads, both sides the same, hot,
Checked for anything visible and nothing, had good oil flow. Engine was running nice, sounded real good, no missing, idled fine. Pisser was not a hard straight jet stream but was what I thought would have been a good flow. Exhaust was clean standard looking smoke.
When engine cooled down I restarted and same thing happened within a couple of minutes so I shut down, engine was again to hot to touch.
Spoke with Skools and he suggested I pull the T stats, I did and though they were definetly used they were not corroded or frozen.
I re installed covers and kept the Tstats out figuring it would run cool now, nope, upon restart heated right up, both sides the same.
The water pump was done for last season by the mechanic of the fellow I bought the boat from and has worked fine no issues till now.
I am planning on pulling the lower unit and checking the water pump out but any other suggestions would be appreciated. The fellow who owns the marina I am at said that the pump could still be bad and the pisser could still flow, especially on the hose because the hose provides pressure, but he also said that it would be unusual for it to get that hot with Tstats pulled and running on a hose and muffs to get that hot that fast.

[Seacrets]

I'd recommend if you pull the lower unit, change the whole pump and not just a kit. If it still overheats, then I'd recommend flushing the water jackets with a descaler.

[Monkey Butler]

I was having an overheat on one bank on my 1986 V6 so I decided to do a little investigating. Take a look at the video on the link below.

Here is what I found when I pulled the T-stat covers and ran the motor. At idle even with a new impeller the flow of water thru the T-stats is not very much. If you look at the video right below the hole for the T-stats there are 4 small holes where water re-enters the head covers. The water then "falls" down thru the head covers and then I believe it goes thru the poppit valve. If the poppit is stuck open it would let the water exit the motor before the cavities in the head covers was full. Notice where the overheat sensors are compared to the water passage. I'd check the poppit valve first. Other than that do you know if the impeller was replaced with a genuine Yamaha part? I've heard that the Sierra's don't pump as well the Yamaha's do so I pay the extra for a Yammie part. Oh, and the pisser can flow what looks like a decent amount before any water actually flows uo to the stats. I noticed that if you rev up the engine and don't see an almost instant change in flow from the pisser then that means you are filling up the block before the pressure rises enough to see an increase at the pisser.

With all that said I also find that mine still runs hotter on one side when on the muffs than when its in the water. When you think about it when the boat is in the water at idle the pump is totally submerged. On the muffs you are relying one the hose to push the water up to the pump and then for the pump to lift it like 3-4 feet to the top of the block. I'd launch and see if you still get an overheat before you throw a lot of money at it.

Good luck, hope you get it resolved.

Steve P.


http://www.monkeybutler.com/boat/MVI_1589.avi

[willy]

Thanks MB, where is the poppit valve and how do you check to see if it is working?

[Monkey Butler]

It is on the lower right of the exhaust cover on the back of the powerhead. It's the thing that looks like a thermostat housing in this picture.

http://www.monkeybutler.com/boat/yammie_teardown/IMG_4548.jpg

There is a rubber grommet in there that you should replace as a maintenance item along the same schedule as your t-stats. Also, Yamaha changed the design later on so it was less likely to get stuck open by debris like sea grass. If you go to

http://www.yamaha-motor.com/outboard/parts/home.aspx

and browse to your motor look at the tab for "CYLINDER CRANKCASE" and parts #48 to 51 will get you the new design.

Also, if the pump was just done then when you pull the lower unit check to make sure that the rubber grommet that the water tube plugs into up in the mid section is in place or you could lose water pressure there too.

Steve P.

[willy]

Thanks, something else for me to check this weekend.
And the pump was done before last season, something happened since the last time I had it out, four weeks ago and today.
Now I did use flush away on the motor, I have the flush system that you attach to the hose. I am wondering if something could have gotten dislodged from the flush and cause a problem. Just reaching for ideas I guess.

[phatdaddy]

willy, i've got a 150 yamaha on a 19' cc and it does the same thing. if i run it on the hose, the horns go off after 10 minutes. i run it on the muffs & a hose to the flush port, no problem. i know its a pain, but try puting it it the water and see if it repeats.

[spareparts]

Yamaha recomeds using the flusihng attachement and the ear muffs , both connected to a dedicated water supply when running their V6's on a hose. Teh Yamaha water pumps have several places(water drains) that will suck air when you run it on a hose. Try using the flushing attachement and the muffs, see if it overheats then. Worse comes to worse, take it to the boat ramp and stick it in the water

[Blue_Runner]

Good info. I don't like running mine on the hose because it doesn't seem adequate. I think I use the double hookup idea going forward. I know you should NOT crank the engine using just the flush attachment...I read that in the manual after a friend said it is ok. Can't believe everything you hear.

[willy]

Well I am going to change out Tstats because I have them out already and try it in the water first as all advise. Come to think about it I was in full hot sun and it was running for at least ten to fifteen minutes when it happened so hopefully that is all it is.
Say a prayer

[RABBITFISH]

Well, I can relate to this problem. Was having the same issue with mine, changed water pump, thermostats, still having overheating. Found out about the PRV valve. Took it out and cleaned it, replaced it. NO MORE PROBLEM!!! Worked like it originally did.. There was not much in the way of dirt, just a little sand, but enough to keep it from making the proper seal. Simple fix and made me more confidant in my motor..:clap: Let us know what does it for you!!!

[willy]

PhatDaddy called it, thanks brother. Went down today, installed the new Tstats cause I already had the old ones out.
Put it in the water and idles it there for about fifteen minutes. NADA, running like a top, no alarms no nothing.
Took her out for a half hour spin, my word these are sweet boats, thank God mine is OK.
Thanks for all the input guys, my wife said "your buddies know their sh!t don't they"
WoooHoo

[phester]

excellent young will. Just in time for Memorial weekend!

[THEFERMANATOR]

Still wouldn't hurt to check the poppet either. Early on they used steel springs and after about 8-10 years they rusted completely out and would not allow water pressure to build up.

[willy]

What I will do Ferm is run the boat this summer, she is running well and I notice the pisser is much stronger when she is in the water. When I pull her this year I will pull the poppit valve, do the water pump and any other things that need attention on an older motor. She is a strong runner, cruises the boat at 28-32 at 3400 rpm depending on load. When I pull the plugs there is always a nice clean burn on all plugs. Can't ask for much more on an 17 year old motor thats all original.
The only thing that I find weird on this hull more than my previous V20 is that she is a counter rotation motor and that she lists to starboard pretty noticeably under power from torque of engine. Sits dead level at rest.
Is that common with all V's with torquey engine power?

[macojoe]

Congrats on the easy fix!!

I wish all these guys were here when I had my Yamaha problems. I had one that kept heating up and was the death of the motor, I did not know anything about the PV.

[THEFERMANATOR]

What I will do Ferm is run the boat this summer, she is running well and I notice the pisser is much stronger when she is in the water. When I pull her this year I will pull the poppit valve, do the water pump and any other things that need attention on an older motor. She is a strong runner, cruises the boat at 28-32 at 3400 rpm depending on load. When I pull the plugs there is always a nice clean burn on all plugs. Can't ask for much more on an 17 year old motor thats all original.
The only thing that I find weird on this hull more than my previous V20 is that she is a counter rotation motor and that she lists to starboard pretty noticeably under power from torque of engine. Sits dead level at rest.
Is that common with all V's with torquey engine power?

If you have a lefty for an engine, then yes she will list pretty good the opposite way. Boats origanally put the driver on the starboard side to counteract the engines torque from the prop. By running a counter rotater the engines torque will actually push the heavier side down even more. Trim tabs would take care of it though, and are a good investment on most any planing hull.

[willy]

Agreed MJ, actually though it was not that valve. It was what Phat said, running on the muffs alone for ten minutes or more as I had done to flush system and to check out fuel line work and in line filter work I had done it heated up. In the water though it runs fine no problem. Yammie idiosyncracy that I did not know about that could of cost me a lot of time or money.
Its good to have friends in low places.

[reelapeelin]

Glad ya worked thru the problem w/no serious $$ outlay...it IS great to have all this collective knowledge to draw from...

The suggestion on the trim-tabs is a good one...it'll cure the list, that's for sure, but they'll also add so much more to to the performance of your hull you won't believe...

Here's an example; comin' down the Tugaloo River the other day, approaching a much larger cabin style boat and knowing the wake he would leave as we passed. Normally the V would rock and roll her way across, approaching those waves at such an angle...have done it a zillion times...w/only a little tab down, she walked her way across in a very stable fashion like never before...VERY pleased and finding new things about what tabs do on every trip...