Cooling system failure

[al27023]

Would like some opinions on sudden cooling system quitting - while running on flusher after cleaning carbs (probably shot myself in foot by using 6 gallon tank with Seafoam and fresh gas - wouldn't go above 4000 rpm in water; looked at tank pickup and found only 1/4 tube to screen).
115 4 cyl 95 Merc noticed a slow stream out telltale and shortly after maybe 5 min the water quit completely - engine got hot. Let it cool and tried again all the while playing with flusher - could see thermostat open but only steam coming out, shut down.
Should I go directly to water pump teardown or should I check thermostat/poppet valve for clogging (could see stream of steam when thermostat opened but no water).
Also opinions on Merc parts vs Sierra pump Kits (for Merc Part # 817257A 2 $67.40 on I-net( Edit - this part no is only for the housing and impeller plate gasket with 4 bolts) (the Merc complete pump kit is 46-43024A7 and costs 119.90)). Are both equal quality?
Appreciate any input you folks can provide - getting tired of working on this thing, just happy it quit in yard instead of a long way away from dock.
Thanks, Al

 

[corm]

Re: Cooling system failure

Hi,
I would do a compression test 1st. Then look at the thermostat ect.
I don't know what quality the seirra brand is these days. I use Merc parts
for the important parts.

 

[al27023]

Re: Cooling system failure

Compression for 1,2 and 3 is 140 and 4 is 120 - 130 (one last checked -couldn't get gauge in sparkplug hole - dropped lower cowl and checked with and without enrichment).
Have pulled gearcase and disassembled pump - doesn't look real bad, impeller is whole, grooves in plate and housing.
This pump has separate base which appears to have seal for pump and gearcase back to back, so guess I'll have to pressure check gearbox after lifting base and replacing seals. Haven't pulled this base yet -will do so after get parts.
Anyone know what size the plug thread is or if it is close to a fitting size that could be made into a test fitting - manuals say it should hold 10 psi for 5 min.
Any other thoughts would be appreciated - thanks for reply.

 

[corm]

Re: Cooling system failure

Hi,

I guess if i was mine I'd take a look at the head gasket. If I remember right the bottom cyl ran cooler than the top cylinder so 10-20lbs difference seems like a lot to me. It may be in spec but i'd look at it anyway.
The water pump groves are normal, but not perfect. So i would put the plates and impeller in it. I usually do not mess with the seals unless I see some sign of leakage. However it is easier to change them now rather than later. I use a rubber tipped air jet to seal in the vent hole. I have always thought the shift shaft seal was more trouble that the pump body seals. I use to do a vacuum test rather than a pressure test but they both work well.

 

[al27023]

Re: Cooling system failure

For info - gearcase plug on 95 115 4 cyl is 3/8-16 thread - have a lawn mower wheel shoulder bolt which I will probably drill thru and tap to a 1/8 npt for a test rig with a bicycle type pump - have had air compressor regulator fail catastrophically and dump 150 psi on hose, don't want that on gearcase.
Will try to finish WP prior to any further compression investigations.
Opinions on the sealer locking material for WP bolts - both Clymer and Merc shop manuals and Merc parts list use Loctite 271 for everything including bolts and OD of seals for WP. My experience with red Loctite indicates that I shouldn't use it on anything I want to come apart whole. Have used OMC sealer in past on WP and LU bolts. It appears that this one was put together (probably at a dealer service with something that ended up whitish with a blue tinge - blue loctite??).
Thanks for any thoughts.
Al

 

[CharlieB]

Re: Cooling system failure

Compression is within acceptable range.

the Merc/Mariner 4 cyl does not have a cyl head or gasket, the block is bored up from the bottom.

Running the motor at speed on the hose is NOT recommended as none are able to flow adequate water to keep the pump supplied, the impeller WILL suck air, dry and cause damage to the sealing edges of the vanes. Rebuild the pump with a quality kit, preferably OEM, they use a slightly better grade material for the impeller.

Gearcase should be tested with BOTH pressure and vacuum, using a mighty vac HAND pump or similar unit, 7 inches vac 7 minutes 6 psi for 6 minutes are acceptable. If EITHER test fails then attention is needed to locate and repair the failure.

Merc Sealer/OMC sealer, av-perm or equiv are all acceptable

Blue loc-tite is not required, Red is definitely NOT to be used.

 

[corm]

Re: Cooling system failure

Hi,

4 cyl 115 Hp Mercs have a head gasket and 15LBS low on one cyl is not acceptable on my engine. Blue is fine for the nuts, ect. Red for the seals.

 

[al27023]

Re: Cooling system failure

Once again, thanks for the input.
Have the foot/WP (Merc kit with base and all parts, gearcase tested) together and installed on motor after much wasted time trying to follow manuals (Merc and Clymer that told me to put gear and controls in forward gear - spent 3 or 4 hours trying to install gear housing to motor that way); Finally put foot and control in neutral and it fell right in, with proper gear results.
Latest question - have thermostat and poppet valve apart and new t'stat and poppet valve diaphragm in hand. There is start of salt corrosion in groove in head for poppet diaphragm bead - should I use 2-4-D grease or a very light coat of one of the sealers (OMC/Merc) to stop the corrosion?
Both manuals I have say the compression should be within 15 psi. Please note that my readings were somewhat disjointed since I could not get my gauge to seal in #4 for two attempts; got 70 and 90 the first two times. After dropping the cowl since I was going to start carbs, I took another reading that held (120) and then hit the prime a time or two to to lubricate the cylinder for the last reading (130).
Thanks again for all the experience and expertise.
Al

 

[corm]

Re: Cooling system failure

Hi,

I don't know anything about salt except what it does to you car in the winter in WI. Glad the compression is ok.
I would sand blast the corrosion off and coat it with paint myself. However some grease or 518 sealant would work well too. The sealer would be the better option to my way of thinking. It will fill in the gaps.