1993 Yamaha T9.94 stroke cooling problem

[n6rfm]

Hi,

1993 Yamaha T9.9 EXHR 4 stroke. Erratic water stream coming from pee hole. Have cleared several obstructions from pee hole. Still poor stream. Will service impeller. In addition, the upper cylinder water bypass outlet (water outlet nipple on top of head at port side) is blocked. Could not clear with 180 psi air stream into nipple. Under the valve cover in the upper left hand corner is a stainless screw which seems to be in line with the upper bypass outlet. Does anyone know if this is a cleanout for the water path? Looks like it has thread sealant on it. Not shown in Yamaha or Clymer manuals. If not, are the water flow channels accessible by removing the exhaust cover on the port side of the power head? And/or, do I need to pull the head off to clean up this mess. Tried removing the thermostat cover and a vinegar flush, but no dice.

Today, things got worse. No flow after motor warm up, then steam from both pee hole and exhaust. Hope impeller is not toast. Flow returned after cool down. Now flow continues from pee hole for ~5 secs after shutdown, but not an impressive stream.

Thanks for any advice. Apologies for lengthy post.
Bob

 

[CatTwentyTwo]

Re: 1993 Yamaha T9.94 stroke cooling problem

I would certainly start with a new water pump, they are not very hard to change out. Do you use this motor in salt water? If you do and your motor is like my 95 T9.9, what you are seeing was normal for me. I don't believe that the design of these motors allowed them to be properly flushed. I always used Salt Away while flushing but had the same problems you are having and tried the same repairs with no luck. It got to the point that it would overheat and fail every time out, I got rid of it with less than 50 hours on it. I worked with a guy that also had a 95 T9.9 with the same issue, he tried muriatic acid but had the best luck with a drill. He drilled and tapped for new cooling water nipples and hoses and last I heard, he was happy with the motor. You are right about the Yamaha manual, it did not show anything about cooling water flow.

 

[n6rfm]

Re: 1993 Yamaha T9.94 stroke cooling problem

OK, will start wil impeller. Yes, salt water use and no access to fresh water for easy flush. Would love to have a cooling path flow diagram. Thinking that I may have to pull off cylinder head to clear the channels. Hoping not to have to remove powerhead from casing to do that.

 

[Yamajoe]

Re: 1993 Yamaha T9.94 stroke cooling problem

when was the last time it had an oil change? the cylinder head/valve train removal isn't too complicated, get yourself the proper manual and ensure you have a new head gasket. the water channels do cake up on these 4 strokes.

 

[n6rfm]

Re: 1993 Yamaha T9.94 stroke cooling problem

Oil change at start of season; about 15 engine hours ago. Only Mobil 1 since new. Have both Yamaha and Clymer service manuals. Will change impeller asap and plan to remove/clean out head over the winter. Thanks fellas!

 

[n6rfm]

Re: 1993 Yamaha T9.94 stroke cooling problem

Here is I found and have done so far...

http://webpages.charter.net/n6rfm/water_pump.htm

Just a few more weeks until haul out. Plenty of time this winter for a real overhaul; clean out salt from power head cooling channels and repair lower impeller housing assembly.

Enjoy the rest of the season everyone!

 

[Yamajoe]

Re: 1993 Yamaha T9.94 stroke cooling problem

You will need to replace with new LU oil seal housing and water pump.