150 optimax water pressure low

[codn]

Hi all this is my first post so bear with me.<br />I own a 150 optimax 2000 model that all the time iv owned it it has had low block pressure at idle approx .5 psi. It has had water pump and housing replaced poppit valves and screens checked and still the same. This problem is particularily bad when the motor is running then shutdown for a few minutes then started back up it takes 3minutes before it gets any pressure and still is not enough to cool the engine without reving. If rpm is not applied alarm will sound due to engine temp. getting too high. I have never let the engine over heat always been awear of the problem but its getting to the stage that I want it FIXED. It has been in and out of of the workshop and never fixed. I bought the outboard second hand with a full merc warranty and have had this problem fully documented from the first time I used the motor, but now it seems that mercury dont want too know about it . Any help would be appreciated

 

[andy6374]

Re: 150 optimax water pressure low

The two most likely canidates for your low pressure at idle problem are: a)poppet valve<br />b)waterpump<br /><br />a.) Even though you had this replaced, this would be my frist guess. When you replaced the poppet valve did replace the diaphragm, grommet, carrier, spring, etc. as well. If the poppet isn't seated properly or the grommet wasn't installed correctly water will empty the block through the exhaust before it can fill the block up with water. At higher RPM's this isn't a problem because you have so much more water flowing and this isn't an issue.<br /><br />b.) Same idea, if it wasn't installed properly you are not getting enough water. When it was replaced what was the condition of the old impeller, if it had broken vanes you need to make sure they aren't clogging anything. Have you checked the new impellers condition. When the water tube is inserted into the water pump, sometimes the water tube folds over the grommet/ring inside the sleeve.<br /><br />Do you have good water pressure at higher RPMs? While your at it replace the tstats. And with the tstat housing off stick a hose down there and flush it out, maybe there is a clog. <br /><br />Good luck and lets us know

 

[timmathis]

Re: 150 optimax water pressure low

5 lbs max ?

 

[andy6374]

Re: 150 optimax water pressure low

Oh yeah, good point Tim. <br /><br />codn-<br />Did you mean 5 psi or .5 psi. 5 psi at idle is fine, but the .5 psi is bad.

 

[codn]

Re: 150 optimax water pressure low

Thanks for your quick reply, yes I mean .5 Psi not 5psi. with just a small amount of RPM the pressure is within spec. It is only at idle when the pressure is .5 psi

 

[codn]

Re: 150 optimax water pressure low

I checked the impeller today, it looked new replaced it anyway also checked the poppet valve couldnt fault it, and flushed water through with the hose. Just a few things <br /><br />1) Is there a screen somewere that I have missed eg. behind the poppet valve? (I did look but not there)<br /><br />2) How is the tube that runs from w/pump to p/head helled in at the top, is it a rubber seal/ grommet, could this be cracked? Is it the grommet that is holding it in position?

 

[andy6374]

Re: 150 optimax water pressure low

Is the pressure up at all?<br /><br />At idle it takes a little bit to fill the whole block with water. Does the pressure ever come up if you keep it at idle?<br /><br />No screen behind the poppet valve. Did you replace all the parts of the poppet assembly? (really the pressure relief assembly). So far this is my best guess. To check and see if this is the problem, ie if the poppet is not seated properly. Take off the poppet housing, and push in the poppet with your fingers and plug up the end that runs from the top of the block to poppet housing as well. Get the motor started (you may need a friend to start for you) and see if any water is leaking around the grommet/carrier/poppet region and see if you physically holding the poppet in place helps increase the water pressure.<br /><br />As for the impeller, what was the condition of the housing and gaskets (where these replaced when impeller was replaced).

 

[codn]

Re: 150 optimax water pressure low

Hi, I posted a few weeks ago about my 150 optimax that had low block pressure at idle. <br />I think/hope I have found the problem. With the lower unit removed I fitted a hose to the main water tube that runs to the powerhead. When I turned the tap on I looked up the mid section to see if the tube was cracked and I noticed water leaking down not from around the tube but from the side somewere (inside the midsection) it was hard to see. What my question is should their be water leaking down this section? Im not talking about the exhaust section but the driveshaft/water tube section. could there be a blown gasket were the powerhead bolts too the midsection, is there a plate between there? I hope Im on to it

 

[uaw9fan]

Re: 150 optimax water pressure low

Nothing to do with your water pressure problem, but you might want to make sure # 8 in the web link picture is clean.It is a screen that keeps particles form leaving the adapter plate and going through the air compressor.If your tattle tail stream is weak,it is a sign that the screen is clogged. web page

 

[codn]

Re: 150 optimax water pressure low

Thanks a heep uaw9fan, I had checked that strainer and it was ok. Got hold of a manual only to find the water flowing down the trunk to be normal. well that saves me a job, im at witts end with it

 

[Grumpy 45]

Re: 150 optimax water pressure low

Hi Codn,<br />Did you find the problem with water pressure. I also have an Optimax with .06 bar at idle but it does not over heat. What is the water pressure at idle expected to be?<br />Regards Dennis