smokin water pumps

[geotek]

Hope someone can help, I have a 1991 OMC cobra with a 5.8 litre. I had replaced the thermostat and water pump housing and impellar and it works fine with the muffs and a hose, but when I put it in the lake it does not draw enough water and after about 12 minutes it gets hot and smokes the water pump and housing. I had checked all the hoses for restrictions and flushed back and forth. After smokin the 3rd pump and housing I contacted a local OMC mechanic who had me bring the outdrive in, he checked it out and found no problems, although he did replace some seals around the pick up tube in the lower half of the drive and put a brand new pump kit on. Well again it works fine with the garden hose but will not draw enough water from the lake and I've smoked another pump kit. I did also check the vent tube and it's clear. Does anyone have any ideas?

 

[jeff13601]

Re: smokin water pumps

Did he check and see if a piece of the impellor could have broken off and gotten stuck somewhere and is restricting flow?

 

[geotek]

Re: smokin water pumps

Yes, I have the impellers, no missing peices. It melts the stainless steel housing for the impeller right into the pump housing. When I took the drive into the shop I flushed water through the inlet hose at the thermostat housing all the way back through the gimble, (I did this in both directions) and checked the power steering cooler as well. <br />Thanks,

 

[jeff13601]

Re: smokin water pumps

Someone put a post a while back regarding overheating do to an exhaust flapper breaking off and plugging the exhaust flow. I do not know if it could cause a restriction at the impellor. Does your thermostat rise fast also?

 

[geotek]

Re: smokin water pumps

I'm not sure what could be considered fast, From a cold start it takes about 8 to 12 minutes for it to get to around 190 degrees, alarm goes off at 200 degrees. I replaced the thermostat with one that's rated at 135 degrees, I can see when it opens buy watching the gage when I have a garden hose attached. But it all appears to works well then.

 

[rodbolt]

Re: smokin water pumps

I have seen some of the late 80's early 90's cobra drives that developed the same problem with no solution. I fought one for a month once and me and 4 other techs could not find the cause. it would run fine most the time but at idle speeds would occasionally lose its "prime" and wipe itself out. the final cure was a johnson crank mounted pump and a thruhull pickup. to use the crankshaft mounted pump you will have to have an alignment sleeve made. this will hold the pump centerline to the crank center line. it will be a small stepped sleeve as the inner bore of the pump and the ID of the balancer are somewhat diffrent. a quick session with dial calipers and you can draw it. a decent machinest can turn it out in 10 min. I dont normally advise reengineering a product but its worked well with the crabbers useing cobra's. I did 15 or so since the late 8o's on both the ford and chevy engines. the chevy engines require no sleeves as the pullys already have the alignment taps. you will also have to manufacture a bracket to hold the pump. some crabbers have actually just tied off the hoses but I make a simple bracket.

 

[marinemech1]

Re: smokin water pumps

theres got to be a reason<br />possible suspects are<br />1 wrong impeller/pump (are you using o.e.m.parts?)<br />2 air/exhaust leak into pump.... put boat in water start engine verifiy water flow lift boat up and watch water flow it should continue to flow until intakes come out of water<br />3 has someone serviced this drive recently they may have put an o'ring where one does not belong sorry to late at night to remember exactly where o,ring gets put<br />4 cracked upper gear housing due to improper winterization<br />grab a manual and trouble shoot problem

 

[geotek]

Re: smokin water pumps

Rodbolt, I have had the drive checked out (also had it pressure tested) and the mechanic can't seem to find a problem and I have replaced all hoses and verified there is no obstruction (including the power steering cooling unit). Replaced several complete pump kits including the housing and it just won't move water from the lake. How expensive is your suggestion and do you know anyone in southeast michigan that can do the work?

 

[geotek]

Re: smokin water pumps

Marinemech1, <br />1) The parts are OEM parts from 2 different marine parts places. <br /><br />2) When the boat is in the water I disconnect the water inlet hose at the thermostat housing, and the water may only flow constant for a few seconds then kind of pulses and is a very weak flow. <br /><br />3) The drive was not serviced prior to the problem <br />although last year it would at times after the boat sat unused for periods of time it would somtimes get hot and all I would have to do is rev the motor and it would start to cool down and run at normal temp at any speed as well as at idle.<br /><br />4) I took the drive in and had a mechanic check the drive out, I asked him to pressure test it while he had it and asked if there was a potential that the upper was cracked due to improper winterization. His reply was your drive is good. <br /><br />Is there a manual that tells you how to verify if the gear case is cracked? could not find anything in a clymer manual except that fluid would be contaminated

 

[geotek]

Re: smokin water pumps

Hello All,<br /><br />I found the cause of my water pump problems today. It turns out that the local marina (McMachen Marine) in Harrison Twp. MI., sold me the incorrect waterpump housing. The pump housing they looked up in their system and sold me then on the second one I purchased they installed for me was actually for a King Cobra Out drive. They look identical except the vent hole on the housing is 3x the size of the corect one for the Cobra outdrive. I did actually question them initially about the vent being on the other side and they responded with, ours is an OEM and the one one my outdrive was not, I felt that they must have been right because after the second housing smoked I picked up the 3rd one from from Mikes Marine (a west marine type store) and they also stocked the incorrect water pump housing which I bought 2 times. <br /><br />the part # that they all sold me was 986272 <br />the correct part # for an OMC Cobra 984461<br /><br />So In closing I wanted to Thank You All for your suggestions and assistance.<br /><br />The guys that found the problem, K&D Marine in Mount Clemens, MI. <br /><br />Well as they say the best lessons learned are usually the most expensive. <br />1)5 water pump kits $280.00<br />2)Outdrive pressure tested and checked out $160.00<br />3)spending 8 hours in 90 degree temps contorted in the engine compartment looking for obstuctions in the water lines. $500.00<br />4)Taking your boat out for a cruise on the lake all day without any problems. Priceless!

 

[Phantom17]

Re: smokin water pumps

Hmmmm, methinks I'd be fighting for some money back....if it was me. (I turn into a royal pri$K when it comes to MY MONEY!!!!! Good luck!