Yamaha 20hp cooling problem

[luddovitch]

Hey guys

I'm having problem with my old Yamaha 20hp 1981. When running at full speed my engine is loosing power after 1 minute or so and the water stream from the pee hole is almost gone. Then when I close the throttle the water stream is there again but with some white smoke coming out mainly from the exhaust but also some from the pee hole. I've tried it without the thermostat without any different results.

I recently changed the head gasket and the exhaust jacket (I think it's called) and made two homemade gaskets for the exhaust jacket, since the old exhaust jacket was rusted out and the engine was taking in water. I've checked the impeller and the impeller housing and it all looked fine to me, but the impeller housing was full of grease or something on the outside, not sure where that could have came from.

Here is a short video of the engine running in a barrel. I'm not sure if the water stream is good enough, it's more like a spray than a steady stream. Also note the grey colored water that flows from the exhaust, is that normal?

Video - TinyPic - gratis värdtjänst för bilder, foton och video

I didn't have this cooling problem when the engine was taking in water. The Engine is running good besides from this cooling problem, a bit hard to start when cold though.

Im I hope you guys understands my problem, my english isn't perfect..

[TownsendsFJR1300]

Looks like your cooling system is pressurized with air or exhaust...Almost more air than water...

The garden hose dangling on the starboard side, where's that go? It doesn't seem to be plugged off if its a flushing device (or hooked up)..

If I was guessing, I'd probably be looking at your gaskets you made up.

If there's some aluminum corroded away from the block (thus the home made gaskets), you may consider, depending where its at, JB weld, some other epoxy or even getting it welded if possible..

Others will chime in, good luck..

[luddovitch]

Looks like your cooling system is pressurized with air or exhaust...Almost more air than water...

The garden hose dangling on the starboard side, where's that go? It doesn't seem to be plugged off if its a flushing device (or hooked up)..

If I was guessing, I'd probably be looking at your gaskets you made up.

If there's some aluminum corroded away from the block (thus the home made gaskets), you may consider, depending where its at, JB weld, some other epoxy or even getting it welded if possible..

Others will chime in, good luck..

Thanks for your answer. Oh, you think air or exhaust are leaking into my cooling system? That would suck..

The garden hose has nothing to to with the Engine, there's a hole at the bottom of my barrel so I need to add more water all the time.

The cooling lines under the exhaust jacket and under the head is pretty corroded yes, will this restrict the water flow and not let enough cold water pass at full speed?

[TownsendsFJR1300]

Well, just from the video it appears perhaps the exhaust is pressurizing the coolant passages, ie blowing the water out-thus no / little cooling..

I've never seen that before, just an estimated guess on my end from what you posted and the visual.

Obviously the corrosion is an issue ESPECIALLY, if its not sealing off exhaust gas from the cooling system. They, of course are two separate systems.

Especially bad if the exhaust IS, blowing into the cooling jackets (displacing water)..

The end of the hose I was referring to was up by the powerhead, right side, it looked like a female end to a garden hose...(Like perhaps a flushing attachment)..


I don't know if it'd be possible to loosen the thermostat housing, start the engine (engine in water tank) and see if just water comes out (normal) OR your getting exhaust/pressurized air coming out with the water-bad.. If the latter, somethings big time wrong

[Jason2tpa]

Well, just from the video it appears I don't know if it'd be possible to loosen the thermostat housing, start the engine (engine in water tank) and see if just water comes out (normal) OR your getting exhaust/pressurized air coming out with the water-bad.. If the latter, somethings big time wrong

Yes, this is possible. When I had a 25hp I used to open thermostat, run engine in a big can and dump salt x into therm housing. The thermostat itself may not open depending on engine temp but if he has an exhaust leak into the cooling system this could be observed with the housing open with engine running.

[luddovitch]

Okay, so now i've tried it without the thermostat cap. When I tried it first it just came alot of water and I didn't see any smoke. But in the second attempt when I kept it at idle no water came and a little bit of smoke, and when I gave some throttle more smoke, as you can see in this video: Video - TinyPic - gratis värdtjänst för bilder, foton och video

What is the next thing I should look at?

[cpostis]

Okay, so now i've tried it without the thermostat cap. When I tried it first it just came alot of water and I didn't see any smoke. But in the second attempt when I kept it at idle no water came and a little bit of smoke, and when I gave some throttle more smoke, as you can see in this video: Video - TinyPic - gratis värdtjänst för bilder, foton och video

What is the next thing I should look at?

Just a few thoughts...
Looks like your water pump is pushing water. Not sure it is getting to the top of your block? Just to be sure, can you feel air pressure in the video (especially when you bump up rpm) from the water jacket behind the thermostat? Could that possibly be steam, and not exhaust gasses?
When you fill up your barrel, you should fill it up well above the lower unit as to ensure you flood the water pump housing. Otherwise, when you first start the motor up, you will be running the pump dry. The few moments while it is dry can ruin your impeller, and/or plastic housing. You might want to pull the lower unit to check the pump/impeller?

[luddovitch]

Just a few thoughts...
Looks like your water pump is pushing water. Not sure it is getting to the top of your block? Just to be sure, can you feel air pressure in the video (especially when you bump up rpm) from the water jacket behind the thermostat? Could that possibly be steam, and not exhaust gasses?
When you fill up your barrel, you should fill it up well above the lower unit as to ensure you flood the water pump housing. Otherwise, when you first start the motor up, you will be running the pump dry. The few moments while it is dry can ruin your impeller, and/or plastic housing. You might want to pull the lower unit to check the pump/impeller?

Yes, I tried it without the termostat before and could feel air pressure when I held my hand over it, i'm gonna try that again though just to be sure. I Think it's exhaust gasses, it has the same color as the exhaust gasses.

Hm, okay I will run it with more water in the barrel, thanks for the tip. I've checked the impeller yesterday and the impeller itself looked fine to me, but im not sure what to look for on the other parts in the pump assembly.

[luddovitch]

Okay, with termostat off and some more water in the barrel it immediately comes water from the termostat houseing.

EDIT: Here's a video of that: Video - TinyPic - gratis värdtjänst för bilder, foton och video

[TownsendsFJR1300]

Ok, that's good...

Now, if your definitly getting exhaust gases into the cooling system, I would be checking where you were, where you know there was/is issues.

Get back to your repairs and check carefully for any evidence of exhaust blowing by where the water jacket is.

Note, Yamaha make a case sealer that works extremely well and if the pitting/opening isn't too large, that may help you seal it up..



Also, all that water (first video), coming from the lower front of the mid section, MAY be coming from the water tube / water tube seal up by the power-head. Many have rotted as seen on this forum. Unfortunately, most require the removal of the power-head from the mid section to access it.

The parts fisch here doesn't even go back that far and being out of the US, probably wouldn't show here anyway.. If you have a shop manual, that should show the water tube/seal etc...

[luddovitch]

Ok, that's good...

Now, if your definitly getting exhaust gases into the cooling system, I would be checking where you were, where you know there was/is issues.

Get back to your repairs and check carefully for any evidence of exhaust blowing by where the water jacket is.

Note, Yamaha make a case sealer that works extremely well and if the pitting/opening isn't too large, that may help you seal it up..



Also, all that water (first video), coming from the lower front of the mid section, MAY be coming from the water tube / water tube seal up by the power-head. Many have rotted as seen on this forum. Unfortunately, most require the removal of the power-head from the mid section to access it.

The parts fisch here doesn't even go back that far and being out of the US, probably wouldn't show here anyway.. If you have a shop manual, that should show the water tube/seal etc...

It sure looked like it came exhaust gases from the termostat hausing, is it any other way to determine that I have exhaust gases in my cooling system?

Yes, I will check the area around the exhaust jacket again. One thing that might casue an issue is that the gasket material I used for the exhaust jacket gaskets is a bit thicker than the original gasket, but not by much. Not sure if this could affect anything.. I will also check the water pump again and take some pictures to see if you guys see anything weird.

Is it hard to remove the powerhead? I never done it before, but I like to learn. I think that would be the next step if I dont find anything else.

[TownsendsFJR1300]

Just your tell tale (pisser) looks like it has a bunch of air in it...

If you could somehow pressurize your exhaust, maybe thru a spark plug hole with the piston down(open exhaust ports) you could hear it in the cooling chamber.

A leak down tester Might work, never done that for your issue.

When you worked on the engine, was there a gasket, or leak or corrosion BETWEEN the exhaust and the cooling system? I gather that's where the issue is. There's MUCH more exhaust pressure than water pressure, thus air into the cooling system..

I'd be checking that area. Can you post any pic's if when you locate that area?

[luddovitch]

Just your tell tale (pisser) looks like it has a bunch of air in it...

If you could somehow pressurize your exhaust, maybe thru a spark plug hole with the piston down(open exhaust ports) you could hear it in the cooling chamber.

A leak down tested Might work, never done that for your issue.

When you worked on the engine, was there a gasket, or leak or corrosion BETWEEN the exhaust and the cooling system? I gather that's where the issue is. There's MUCH more exhaust pressure than water pressure, thus air into the cooling system..

I'd be checking that area. Can you post any pic's if when you locate that area?

I will see if I can find anything to pressurize the exhaust.

The issue I had before was that the cooling jacket was rusted up and let water into the cylinders and all the water soaked down the spark plugs. I think it's called cooling jacket, I will post a picture of the new one here:

kylmantel.jpg

It's is number 30 in this pic, number 31 is the gaskets i've made myself:

skiss2.jpg

There are some corrosion in the water jackets in the block and on the "lid" (number 29) but I could not see that it was corroded all the way through

I will remove this again tomorrow and take some pics.

[TownsendsFJR1300]

It looks, with the pic's you posted and how I interpret it, that's probably where the exhaust is leaking into the coolant system (somehow)...

I would think it would blow out the sides into the under cowl area, but apparently isn't.

Any bad / corroded surface area (poor sealing) could cause this. Again, it doesn't take much exhaust pressure (and at higher RPM's is a bunch) to blow past the gasket..

You should be able to see some black / soot where its leaking at once the new cover is off..

[luddovitch]

It looks, with the pic's you posted and how I interpret it, that's probably where the exhaust is leaking into the coolant system (somehow)...

I would think it would blow out the sides into the under cowl area, but apparently isn't.

Any bad / corroded surface area (poor sealing) could cause this. Again, it doesn't take much exhaust pressure (and at higher RPM's is a bunch) to blow past the gasket..

You should be able to see some black / soot where its leaking at once the new cover is off..

Okey, thanks for all the help so far. I will look at this tomorrow after work.