Question for the experts on cooling system

[dngharvey]

1998 Yammie 115 two stroke. Had it running on the trailer to get ready for storing and noticed that one cyl bank never got very warm at all while the other was hot to the touch. ( you could keep contact so not real hot ) The pee stream also did not get warm, water coming from the prop was lukewarm and plentiful.
Ran it for probably twenty minutes, should have been plenty of time to reach operation temp. Headed for the keys in January and want to be as ready as possible.
Time to change the t stats? Mainly a fresh water boat but flushed faithfully when in warm Florida waters.

[pstephens46]

Well....you could remove one stat at a time leaving cover off to make sure there is a good flow of water coming from each side. Water will get all over motor but who cares? Water from pilot hole never gets very warm.

This experiment also assumes running on muffs. Not blowing seawater all over the motor....

[99yam40]

stat on that one side may be stuck open so it stays cold.
pull them and test them or replace with new

but I would want to make sure they work in spec

[Jason2tpa]

I have the same hp engine and year. Doesn't sound concerning at all. One bank will always be warmer/cooler than the other. Since you cold started and ran engine on flush, as opposed to flushing after operating under load, it's quite possible 20min of flushing wasn't enough time to bring up temp for both banks and T/T stream to get warm. And if you were doing this flush today, the air temp was in the 60s (florida) so this would only prolong engines ability to warm up to operating temp.

I also recon if one or both stats were stuck closed, you'd witness the opposite of what you felt...engine banks and T/T stream would warm very quickly, and possibly even overheat.

[TownsendsFJR1300]

If the thermostats are working properly, it shouldn't take 20 minutes of warm up time, that's what their for..

Low 70 F water(winter), my cold idle drops in about 2 minutes to 700 RPM (F150)

Agreed, pull thermostats and test. If they pass, run on muffs with T-stats out and check for water flow.

When was the last time the water pump was replaced?


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[99yam40]

motor running too cool would not come from not enough water flow, it would come from too much( stuck open stat or stat missing completely)
some people will do strange things to a motor sometimes

[dngharvey]

Thanks all for the input, always a bunch on here ready and willing to help.
Have had this setup for nearly three years and has been flawless, new impeller when purchased and pee stream still appears strong and no hint of running hot.
I'm thinking change out the stats based on what you guys have offered, what can it hurt.
Thank you again!

[TownsendsFJR1300]

Thanks all for the input, always a bunch on here ready and willing to help.
Have had this setup for nearly three years and has been flawless, new impeller when purchased and pee stream still appears strong and no hint of running hot.
I'm thinking change out the stats based on what you guys have offered, what can it hurt.
Thank you again!

You should really replace the water pump, grease the splines, etc. Three years is a long time for it...

[boscoe99]

I would put it in the water and see how it operates.

The cooling system being tested when the motor is being run on flush muffs is about as valid as testing for voltage with no electrical load on the system.

It is quite simple to check the thermostats for proper operation and simple to test the water pump for water pressure. Go to Home Depot and buy a pressure gauge. Install it on the garden hose flush fitting if the motor has one.

[TownsendsFJR1300]

You can't see the condition/set/cracking of the rubber impeller with a pressure gauge.

I don't care to wait till there is an issue and have to pluck parts of the impeller out of the engine... Cheap insurance

Just to grease the drive-shaft splines alone, the LU should be dropped..

[boscoe99]

You can't see the condition/set/cracking of the rubber impeller with a pressure gauge.

I don't care to wait till there is an issue and have to pluck parts of the impeller out of the engine... Cheap insurance

Just to grease the drive-shaft splines alone, the LU should be dropped..

That is correct. But you can see if the impeller is providing the appropriate output by simply installing a pressure gauge.

If the impeller is providing rated water pressure then move on to the rest of the cooling system to determine where the cooling system problem may be. It won't be the impeller.

On the other hand if the impeller is not providing rated water pressure then I would certainly start there. But the motor needs to be in the water in any event. Not with the boat on a trailer.

Now the impeller, if providing rated water pressure, may be getting old and brittle or taking a set. It would not be a bad thing to replace the impeller and/or the complete water pump.

Got me to thinking that Yamaha needs to get in touch with Evinrude's supplier of impellers. They only need to be changed every five years or 500 hours.

[TownsendsFJR1300]

Yamaha marine (and more so Yamaha motorcycles) are pretty "aggressive" with maintenance intervals..

IE, brake caliper SEALS, REPLACE every TWO YEARS. In real life, you can get about 5 years out of them... I can go on with other things.

The marine world of course is much harder than street machines..

Ask RB how many drive-shafts he's had to cut due to lack of maintenance.
How many posts have there been (especially the smaller engines) of impellers "that were good" until actually checked and parts missing.

I don't care how well the pressure is at the TT, THREE years, shafts need grease, rubber hardens/goes away, normal wear and tear... Seals UNDER the wear plate fail, (and then water intrusion to the LU) and it snow balls into something bigger...

Regular maintenance now, or bigger issues later..

That's my story and I'm sticking to it...


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[pstephens46]

500 hours is a lifetime for an ETEC!

Seriously though, you don't have to maintain anything. Then all work is a repair.
Think of Solo. He didn't do anything until an alarm sounded. 12 year old thermostats!

[panasonic]

Thermostats are cheap and easy to replace and/or test..I would start there.

As already mentioned and debated, it would be good maintenance to drop the Lower Unit and at the very least inspect the water pump and grease the shaft splines. But again if you go that far putting in a new water pump kit will give you peace of mind and for a small price.

Good Luck.

[panasonic]

Yamaha marine (and more so Yamaha motorcycles) are pretty "aggressive" with maintenance intervals..

IE, brake caliper SEALS, REPLACE every TWO YEARS. In real life, you can get about 5 years out of them... I can go on with other things.

The marine world of course is much harder than street machines..

Ask RB how many drive-shafts he's had to cut due to lack of maintenance.
How many posts have there been (especially the smaller engines) of impellers "that were good" until actually checked and parts missing.

I don't care how well the pressure is at the TT, THREE years, shafts need grease, rubber hardens/goes away, normal wear and tear... Seals UNDER the wear plate fail, (and then water intrusion to the LU) and it snow balls into something bigger...

Regular maintenance now, or bigger issues later..

That's my story and I'm sticking to it...


.

Never seen that brake caliper seal maintenance reference before Scott. That seems way overboard to me...The only time I every knew anybody, including myself, to change brake caliper seals is when there was evidence of leaking.

Dirt bikes and Quads are mostly what I have seen with leaking brake calipers and I suspect that is the result of running in the dirt and muck all the time.

That come from your Bike manual?