Coolant leak - replaced water circulator still leaks coolant (freshwater)

[FeelinNautiNJ]

Fitted boat with new engine with freshwater cooling system (why not?). Ran it in driveway fine, started fine on water. Took it out this year and belt broke and overheated briefly, got towed back. Replaced belt, looked for cause and noticed alternator pulley had a little rust (caused break?), original alternator (1997 Wellcraft, 3.0L 4cyc 140hp) so replaced it and ran fine again until I took it out on the water. Noticed the engine seemed to feel a bit bogged, and then coolant leaked out of circulator/water pump on engine. Got towed back and decided that the circulator was at fault... I was very surprised to see the older water pump was reinstalled on the new block by the professional installer despite buying a new long block but anyway I am now having problems with my attempt to repair the engine with a new circulator ... The bolt at top left the pump leaks. I tried resealing several times. Making sure to remove the old gasket. Tried also using Permatex gasket maker as well... same problem. From what I can tell surface on mounting appears clean each time. Do I assume that the new pump is faulty? Could there be some other engine related issue that allows the coolant to weep out the bolt? Also, with the last test I noticed a tiny bit of oil residue on the trailer where the exhaust... not sure it MIGHT have been there before but I'm worried that the "new" pump could have damaged something else? Could belt tension play a factor in either the original installation or when I put the new belt on?

 

[bruceb58]

The pump should be installed with the paper gasket ONLY...no sealant.

Also. I know it sounds like overkill, but tighten down all the attaching bolts with a torque wrench to spec.

 

[FeelinNautiNJ]

bruceb58 - thanks for the comment. I'm sorry but I probably didn't make it clear in my first post, but the first time I installed it, I only used the paper gasket and torqued to spec (20lbs/in2) using a crosswise fashion (10 then finally 20.. I've seen different specs... some say 15lbs, others 20-30, so I opted for the "middle" 20). I only added gasket maker after I started doubting the quality of the gasket of the first install. I ordered a new pump (this time GM instead of sierra) and will try again based on your response and not use the gasket maker again... Thanks!

 

[bruceb58]

I ordered a new pump (this time GM instead of sierra) and will try again based on your response and not use the gasket maker again... Thanks!

I am not a Sierra fan. When you take off the old pump, put a straight edge across it and see if it's really flat.

Check for any burrs or scratches on your engine pump mating surface. Make sure all old gasket material is gone. I carefully use a razor blade to make sure it's clean. I also use gasket remover if they are stubborn and always wipe down the surface with lacquer thinner at the end.

I have been down this road with autos so I know what you are up against.

 

[FeelinNautiNJ]

Ok.. still having issues - so frustrating!!! Installed new pump (GM)...(much better quality btw) Cleaned surface completely removing old gasket and then cleaned again with a little solvent for any residue. Checked flatness - seemed good. Torqued to 20 crosswise with gasket carefully aligned between engine and pump. Used a calibrated digital torque sensor to check on each bolt. Reinstalled belts at 50lbs in of tenion (about 1/4-1/2 inch deflection) Filled coolant, muffs on with water and started engine. 30 seconds into it while cranking- noticed drip from pulley...leaking from weep hole then scraping sound, so I shut it off -what the "blank"??! I've replaced water pumps on cars as well but not on a gm. What is going on here? Is there too much pressure from the bidirectional pump (possible?)
Does pressure build up when the thermostat is closed to the point where it would come out of the weep hole? ?

I installed the freshwater kit last year and everything up to this point was running fine but when going over the directions from the kit there is an optional "heater" which acts as a bypass from the thermostat housing - even though I don't have a heater, should I also add another line run from the thermostat housing to the exchanger (see second page on diagram) or does the pump simply "mix" until the temp rises and it opens?? (maybe I'm getting paranoid but I'm stumped)