89 200HP Mariner Low Water Pressure - water pump and hoses flow fine

**tristanlee85** · 06-21-2018, 08:05 AM

I've been battling this water pressure issue for 3 or 4 seasons now and after reading numerous threads and doing my own inspection, I've still not resolved it. At idle, I get no pressure reading. The pee hole just drips. Without being under load in a big container of water, I get about 6psi @ 4000rpm. Under load, say 40 - 60mph it's ~10psi. I do have the nose cone. Even under those higher rpms, the pee hole still isn't a hard solid stream like I see on most outboards.

I've put in multiple water pumps, 1 every year actually even though they show no signs of wear. I make sure to use the guide sleeve and the rubber grommet in the housing so that the copper tube seats properly.

I've taken off all of the cooling hoses and blown air and water through them to make sure they aren't plugged.

It doesn't overheat at idle or low load even with low rpms. It only overheats at higher rpms. I'm ordering 2 new thermostats to change just because it couldn't hurt.

I've read about the poppet valve. I'm not sure of its location. I thought directly on top of the engine, but I look there and there's an adapter for my water pressure reading. Though I think a bad poppet valve would give me more pressure, not no pressure.

The copper tube has a lot of play in it, though it sounds like this is normal when not connected to the lower unit since it's also just a fit into a gasket, though I am wondering if the majority of my water isn't making it all the way into the engine because of a tube leak. I think I can just pull it out and inspect?

Thanks in advance...

**bullet123** · 06-21-2018, 01:11 PM

Poppet is towards bottom of block, starboard side. looks like 2 circles side by side

**Merc 2.5** · 06-21-2018, 01:16 PM

Max water pressure is 10-12lbsish, u call pull copper tube and look in mid with flash light ,should b rubber washer thing that seals it in,, is it running hot ?

**bullet123** · 06-21-2018, 01:19 PM

It must depend on the cone job. I get 2-4 at idle and 22-25 at wot on my coned lower. He said it gets hot at high rpms.

**bullet123** · 06-21-2018, 01:23 PM

It could be poppet problem, but sounds more like thermostat/blockage issue

**Merc 2.5** · 06-21-2018, 01:24 PM

I've never actually read n manual bout pressure but with that said I've always heard 2-5ish idle 10-15maybe wot. Any more pressure and it's moving to fast to pull heat out of the block like it's suppose to, again with that said. My last 2.4 had water pressure like ur talking about then I put the same lower on the modvp and had water pressure in (spec) I thought, maybe some one can clear it up for me

**bullet123** · 06-21-2018, 01:26 PM

Did both motors have poppets?

**Merc 2.5** · 06-21-2018, 01:27 PM

Yep, I was wondering if 2.4 with all pressure was bad?

**Merc 2.5** · 06-21-2018, 01:27 PM

Poppit that is

**Merc 2.5** · 06-21-2018, 01:31 PM

Not hijacking this thread lol, my best advice is go ahead replace poppit, and least pull stats and test them b4 buying new, and your whole water pump assembly is new?

**bullet123** · 06-21-2018, 01:32 PM

generally if you use thermostats you use poppet valve- if you use washers you pull guts out of poppet and cap it. Im sure someone will get on here and tell us proper pressure. 10 seem very low to me at wot.

**Merc 2.5** · 06-21-2018, 01:33 PM

And I agree also ,which is why I'm curious also , stats and poppit, is cheap insurance if u haven't replaced them anyway

**bullet123** · 06-21-2018, 01:49 PM

Poppet might be plugged and not letting in more volume of water. When poppet opens, I don't think thermostats do much. One other thing to consider is "ram" waterpressure . When Im wot I am doin 90ish. Maybe that is why my psi is higher?

**tristanlee85** · 06-21-2018, 03:15 PM

I went ahead and order 2 new thermostats and poppet kit. I've had the thermostats out before when I checked the lines for blockage and visually they looked fine, but I never did do a boil test to see when they open or if they were already stuck in a position. I found the poppet. Looks like I need to take the lower cowling off to get to. I suspect that perhaps that valve is possibly stuck open, or a combination with a thermostat issue causing the pressure not to build. Idle and lower speeds, even though water pressure is low, it never overheats. But trying to do 50 - 60 consistently it gets hot real quick.

Water pump housing/components are brand new as of yesterday. And the one I took off that I installed last year was also in great shape.