1998 90 HP clogged water jacket-need cleaning process tips

[Bob]

Thanks All. I’m going to inspect/replace t-stat and pcv and also drop the lower unit and pump a vinegar wash for 24 hours. I am making the assumption that I should run the wash with the stat out but the PCV in place? Thoughts?

[99yam40]

yes pull the stat and put cover back on.
make sure PCV is good and in place to keep from it just dumping out the exhaust.


not sure how good vinegar will clean.
might drop the stat and PCV parts/covers into a container of that vinegar to see if it does what you want it to before trying to flush the motor with it

[Bob]

Thanks I'll start there and see what happens. The pre-treatment inspection of the Tstat and PCV should be a good indicator. I'll do a concentrated vinegar flush.. I purchased a 600 gph pump today at harbor freight with an assortment of fittings. I'll start with a hot mix and run it for 24 hrs and then replace the stat and pcv with new parts and then sea trial. if still not satisfactory I'll address pulling the heads. My big concern is frozen bolts.

[pstephens46]

yes pull the stat and put cover back on.
make sure PCV is good and in place to keep from it just dumping out the exhaust.


not sure how good vinegar will clean.
might drop the stat and PCV parts/covers into a container of that vinegar to see if it does what you want it to before trying to flush the motor with it

Never had much luck cleaning anything with vinegar. Makes a pretty good marinade. You can buy concentrated versions that are much stronger than grocery store stock. I see 30% available online.

[Bob]

Has anyone had any luck with Bartenders friend> It has Oxalic acid as does Rydlyme

[ausnoelm]

It's a lot more complicated than you think, it's not simply salt build up, hot water will dissolve salt easy as pie, you have all sorts of minerals that have hardened in the water passages, even if used in fresh water (kind of like stalactites) and unless you use mechanical force, or something that will not only "eat" this stuff away, but it will also dissolve metal too, some of these vinegar and proprietary products can buy a bit of time by clearing deposits just enough to allow enough circulation, but, they will not fully clean them out.

[Operaman]

Just did this on my 2000 200hp ox-66. Every bolt came out easy with a 1/4 inch ratchet. Very lucky.
I ran everything through it including Barnicle Buster in the spring for hours. New everything. Had no water pressure
at the gauge. Finally the alarm started to go off. So, my brothe and I did the head removal while the boat was in the water.
Wellcraft 270 Coastal. Yes, some built up hard minerals, mud and salt in passages. The main reason I believe for blockage was
the gasket between the head and water jacket. It was collapsed, falling apart when we removed the water jacket. As above atated, cleaned evry bolt, passage way stc and now have great water pressure and no alarm. Best of luck

[Bob]

The very first bolt on the T-Stat cover snapped off even with 1/4 " rachet. Heat and then cooling to eliminate expansion did not help with the rest of the water jacket cover bolts as a total of 4 broke off. All Head bolts came out with no evidence of any anti-seize compound on any bolt. The water jacket passages on the head were not too bad and around the cylinders in the block mostly clear. The cause of the overheating was most likely a somewhat blocked t-stat and totally blocker poppet valve. I subsequently soaked all of the bolts and T-stat in straight vinegar for 2 days and they came completely clean. I did the same with the head and it softened most of the gunk in the passages but did not allow me to budge the broken studs in the head even after using penetrating oil and heat. I have 4 broken 3/16 studs two of which are flush with the head. Suggestions?? Drill and ez-out? A replacement head is $252.00!! I would rather buy a used head if I can get it at the right price. Thoughts? Thanks for your expertise.

[pstephens46]

The very first bolt on the T-Stat cover snapped off even with 1/4 " rachet. Heat and then cooling to eliminate expansion did not help with the rest of the water jacket cover bolts as a total of 4 broke off. All Head bolts came out with no evidence of any anti-seize compound on any bolt. The water jacket passages on the head were not too bad and around the cylinders in the block mostly clear. The cause of the overheating was most likely a somewhat blocked t-stat and totally blocker poppet valve. I subsequently soaked all of the bolts and T-stat in straight vinegar for 2 days and they came completely clean. I did the same with the head and it softened most of the gunk in the passages but did not allow me to budge the broken studs in the head even after using penetrating oil and heat. I have 4 broken 3/16 studs two of which are flush with the head. Suggestions?? Drill and ez-out? A replacement head is $252.00!! I would rather buy a used head if I can get it at the right price. Thoughts? Thanks for your expertise.

EZ outs not preferred around here...drilling and installing heli coils seem to be the safest method.
where is Panasonic? Would he recommend the burr to level the remains to get a good start?

[ausnoelm]

Good quality left hand drill, go slow, start on centre, keep going straight, leave the EZY outs in the tool box.

[zenoahphobic]

I think easyouts can break and leave you with a much harder steel stuck with the remains of the bolt. The bolt remains could also be expanded, making them stuck harder when this happens.
I think a left handed quality drill bit(s) the go. You may need a range because several enlarged holes in the stainless steel bolt will need to be drilled, maybe to full bolt diameter, before the remaining bolt "tube" turns out with the drill turning anticlockwise. If you get to near full diameter you may have wandered off course, and then a helicoil should be used after carefully getting the "hole" painstakingly back to centre again before using the helicoil drill bit and tap.

[TownsendsFJR1300]

The very first bolt on the T-Stat cover snapped off even with 1/4 " rachet. Heat and then cooling to eliminate expansion did not help with the rest of the water jacket cover bolts as a total of 4 broke off. All Head bolts came out with no evidence of any anti-seize compound on any bolt. The water jacket passages on the head were not too bad and around the cylinders in the block mostly clear. The cause of the overheating was most likely a somewhat blocked t-stat and totally blocker poppet valve. I subsequently soaked all of the bolts and T-stat in straight vinegar for 2 days and they came completely clean. I did the same with the head and it softened most of the gunk in the passages but did not allow me to budge the broken studs in the head even after using penetrating oil and heat. I have 4 broken 3/16 studs two of which are flush with the head. Suggestions??

Simply find a good machine shop and have them do it correctly. Yes a little more expensive but your head will be like new, no messing with new / used heads, etc.
They have specialized equipment that can do it easier.

BTW, Heating the area while spraying a penetrant and WHILE STILL HOT, is when you try to remove the bolt. Letting it cool defeats the purpose of heating (for the most part).

[rodbolt17]

dunno.I just use the correct taap drill,preferably a bullit-point.
carefully center punch it after making the end flat with a file. use a good variable speed drill.
then I simply drill it.
however I have been drilling and tapping broken bolts over 40 yrs.