1998 90 HP clogged water jacket-need cleaning process tips

[Bob]

Dear Good Yammie Mechanics; I have a 1998 90 HP that is overheating at high RPM I have never pulled the head to clean the cooling system. I would surely appreciate your expertise on do's and don'ts, especially when it comes to which tools and methods that I can use to clean the water passages. After I pull the exterior water jacket and cylinder head may I use a wire wheel and or a pressure washer on the head and water jacket cover only. I know that I will have to pick the crap out of the block. Please help.. I need to get started ASAP. thanks in advance Bob in South Carolina

[ausnoelm]

You will just have to use whatever will get in and dig the crap out, it's going to be hard as a rock, and won't just wash out.

[TownsendsFJR1300]

Plus 1 ^^.

Scraping with a small screw driver initially should work. Then a small wire brush "wheel" on a drill should speed things up.

It's a PIA and you'll likely find the lower block water passage the worst with salt...

If the bolts don't break loose initially, use heat, penetrating oil, patience. I would NOT just strip / break it off.

For re-assembly, I'd either run a tap thru the threads or clean very well with a bolt and brake cleaner.. (get it CLEAN)..

[robert graham]

Are you absolutely sure that your high RPM overheating is due to plugged cooling passages....and not some other issues like the water pump, thermostat or PCV?......A 20 year old motor could give you problems on disassembly...like frozen/broken bolts,etc....

[mesias_yam]

Be ready for some broken bolts... Before that I would try flushing with RYDLYME Marine.

[Bob]

This situation only occurs after about 30 seconds at WOT (approx 5000 rpm) I have changed the impeller in the pump and the stream out of the "pee" hole is strong! Would it be best to just begin by inspecting the T-Stat and maybe taking a run with the T-stat removed. It's summer here in SC and the ocean is warm. How do you deal with a broken bolt? Do you have to use heat and and penetrating oil on the stud remaining in the block? I appreciate any and all previous experiences from the members.

[ausnoelm]

Broken bolts usually need to be drilled out, some skill, a quality left hand drill, and slow going will do the trick, do NOT use ezy outs, inspecting the thermostat might give a clue to the amount of build up, don't run with no thermostat.

[robert graham]

Double check the pump, housing, thermostat and PCV....removal of head bolts would be a last resort for me.....pull boat out of water, put motor in a 55 gallon drum of water and run it there, then you can add acid/Rydlyme/whatever to help flush motor.....when you have thermostat/PCV out for inspection look in there with a light to see how much deposits you may have....

[Bob]

The rydlyme 1 gallon concentrate only makes 2 gallons of solution when diluted. How do you use only 2 gallons of solution to flush the cooling system??

[99yam40]

drop lower unit and hook up a pump to the pipe heading up to power head, catch all of the solution and keep it recycling

[Bob]

Thanks for the suggestion! Suggestions for a pump- a small sump pump? It would need to be a low pressure /low volume pump ?

[99yam40]

I have read some have used small 12 volt bilge pumps or live well pumps

[ausnoelm]

It's not going to get hardened crud out of the water passages, digging it out is your option, miracle additives are OK as a preventative measure, but not once it's built up.

[robert graham]

I'm just saying that your problem may not be deposits....it may be in the water pump, thermostat or PCV ....best to be dead sure these are in good working order first...

[TownsendsFJR1300]

From Rydleym:

http://www.rydlymemarine.com/assets/...structions.pdf

As noted above, you can modify the procedure...

Check other maintenance parts, try Rydlem, then be prepared to remove the head (very, very likely).

Just as a side note, we did my neighbors 200 Yammy (two stoke, same issues exactly) awhile ago (two heads). Not a broken bolt..

Any bolt that was froze, worked it wIth heat, penetrating oil, back and forth, even just slightly initially, etc - just DON'T FORCE IT.