How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

[Jerry_NJ]

I have a 9.9 HP and I am not sure the engine is getting proper cooling.

I have ran it for short times in a lake with water temps around 60 degrees and find when I remove the engine cowling I can touch the engine block and even the heads and they do not feel hot. Does this mean/prove the engine is getting reasonable cooling, at least not over heating?

Is there a better method to test beyond seeing the pilot (pee) hole flow of water?

 

[ondarvr]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

You didn't say what brand or year of motor this is, it makes a big difference, some have thermostats and some don't.

 

[Jerry_NJ]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

The subject is a circa 1995 Yamaha 9.9 2 cycle, looks like new, purchased used as part of a boat deal last winter. The owner had the Yamaha as a spare and used a 25 HP on the boat as his regular engine. I have tried with no luck on getting some exchange of information on the Yamaha forum, nothing, not a single reply. Do you suppose the Yamaha are such durable engines no one has any problems with them : ) ??

I have only tested the engine and can not find a user's manual. Yamaha provides manuals on the web back to 1998, I think it is. I looked at that engine and see some basic differences, eg the location of the transmission lever.

When I started this engine, on a pull or two, I could not see any pilot (pee) hole stream so I removed the cover to "watch" the engine temperature. I ran the engine mostly at moderate speed and there was no indication of the engine being even hot, just warm, I could put my hand/finger on it after running for about 10 minutes. My conclusion is either this engine doesn't have a pilot stream, or it is blocked or the impeller needs to be replaced. The lack of heat at the engine suggests to me it is getting cooling water. A Yamaha owner at the lake, he had a 4 cycle at this time, said the pee stream would not show until the thermostat opens, I think that is not correct.

Yes, these are topics for the engine forums, but having no luck there I though I'd try to get a "finger" test method that is though to be an acceptable way to detect engine overheating before it gets damaged from the overheat. Overheating can occur even if the pee stream is present, that is just a verification that the impeller is generating water pressure up into the engine.

 

[ondarvr]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

Does it have an outlet for the pee stream......all the Yamahas I've run have had one (haven't used this year or model though). It is very common for them to become plugged, just stick a piece of wire in it, or use an air nozzle and blow in it, it should flow after that.

It will over heat rather quickly if no water is flowing through the block and you would be able to feel it.

Don't look for a manual, look for parts diagram, it will show where the thermostat is and how the pee tube is plumbed.
http://www.oemparts-junction.com/fiche_section_detail.asp?section=206406&category=Outboard Motors&make=YAMAHA&year=1994&fveh=4787

Didn’t see a 1995, but this is a 94’ it shows the thermostat and what appears to be the pee tube (part #19)

 

[Sea Rider]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

If engine has been properly rinsed after each outting, will have an impeccable water circuit free of salt crusts, thin salt layers. If been used at sea and poorly or not rinsed at all expect what mentioned before. Not an issue if used in fresh water. Don't expect to fry a steak on cylinder head, will be warm enough, but not as to burn your finger at least at idle/fast idle speeds.

When portable engines overheats due to clogged internal water paths, thermo failures, engine will begin to miss due to head gasket failure, on worst scenario, will smoke worst than a Asian, blowing head gasket included.

Being a 18 year oldie, for your peace of mind and good sleep, remove thermo, inspect, clean if in good cond, or replace for a new one along with thmo gaskets too. Also check water pump impeller condition, place a new one if blades are severely deformed, dried out, worn.

Happy Boating

 

[Jerry_NJ]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

Thanks, great to get the great help I have seen in past.

Looking very carefully at the bottom "pan' of the engine compartment I did find a very small diameter hole, no more than 1/32" I'll guess. I stuck a piece of wire in that hole and didn't feel any blockage. Then with the cowling off the engine I saw a hose (plumbing) from the port side of the engine connecting directly above this hole, so I pull the hose off the block and blew into it with my mouth... I could feel air coming out of the small hole (must be the pilot/pee).. this confirms that now at least there is no block between the block and the hole. I believe the engine never saw any salt water, in fact I think it saw no more than a few hours of any use - looks brand new.

The other mystery on this engine is where is the cooling water intake. The sides of the lower unit do not have the set of intake channels I see on my Evinrude and I see on more recent models of the Yamaha. There is an intake under the anti-cavitation plate, I took that screen off and it is perfectly clean. I think the biggest problem would be from small insects getting in and plugging stuff up. If this is the cooling water intake, only one good size intake, the garden hose "ear muff" water supply tool would not work. There are a couple of small (maybe 1/4") holes on the side were I'd expect to see the water intakes. I suppose these could do the job, but I doubt it, that's why I am looking for even a owner's manual which shows this type of information.

I'll look at the link to parts.

 

[ondarvr]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

I use the normal muffs on my small Merc and it has the same intake on the bottom of the AV plate, just put the hose side of the muff on the bottom of the plate and the other one on the top. It works on the Merc, might on the Yamaha too.

Then pull out the thermostat and make sure it works.

http://www.oemparts-junction.com/fiche_section_detail.asp?section=206406&category=Outboard Motors&make=YAMAHA&year=1994&fveh=4787

YAMAHA, 9-15EHS-15MHS-9EHS - CYLINDER - CRANKCASE

 

[ondarvr]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

I tried to link the exact page but it would only link to the menu page where you need to click on outboard, then Yamaha, then the model I posted above, then cylinder, it will then show the diagram you need.

 

[Jerry_NJ]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

Thanks for sticking with me on this, but

When I go to the parts page every thing goes well on Outboard, Yamaha, Year = 1995, but I can not find 9-15EHS-15MHS-9EHS
is that for a different year? I tried all the model 9-anything and every one shows a 4 cycle upper engine cover.

But thanks on the muffs idea, you have also confirmed my guess that the cooling water intake is just above the prop, on the bottom side of the Anti-Cavitation Plate. Every other engine I have gotten close enough on to care where the cooling water intake is has them on the both sides of the lower unit area, and the 1998 Yamaha 9.9 shows it has the intakes there too. I had my doubts because that seems to me to be a rather turbulent area to try to pick up water, get water and given the exhaust gas coming out of the prop the intake could get some hot air too, right?

 

[ondarvr]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

The 95' isn't listed, look at the 94' same motor. Sometimes the year isn't correct, my 05' merc has both 04' and 05' dates on it.

 

[Jerry_NJ]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

Thanks, the 95' is a guess. I have not yet found any reference that gives me such information based on the numbers on the identification plate on the motor.

 

[greenbush future]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

If the outboard is new to you, it would be a great idea to just change the water impeller out so you know it's running right. They aren't hard to do, but if you are unsure, take it in for this maintenance item, so you don't overheat your outboard. With little or no water coming out the tell tale, I wouldn't run the motor till it did. Typically all this stuff is done at the end of the season, when you have time, but either way you will know it's done.

 

[Jerry_NJ]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

Thanks, I'm still trying to learn what model/year the engine is. I have found the identification plates, there are two of them on the engine, but the numbers there don't match anything I have found on model numbers.

It has been suggested too that I buy a "kit", not just the impeller, that way I get new o-rings and the like. Still, I need to know which kit.

 

[greenbush future]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

Thanks, I'm still trying to learn what model/year the engine is. I have found the identification plates, there are two of them on the engine, but the numbers there don't match anything I have found on model numbers.

It has been suggested too that I buy a "kit", not just the impeller, that way I get new o-rings and the like. Still, I need to know which kit.

I would take the #'s down and call the Yami dealer for specs on the outboard, then shop for your best "kit" price on the water impeller.

 

[Jerry_NJ]

Re: How hot doesw a 9.9 HP 2 cycle engine get at cylinder heads?

Thanks, I took the time to write down what the Yamaha ID plate shows:
Model: 9.9 LD
Code: 682C L
Serial: 386490

It is a long shaft engine, which may be reflected in the Model letters "LD". Long Drive? There is nothing there that suggests a date to my mind. The code could translate to a date.

I'll check the web for Yamaha dealers in my area.