Too much water pressure at idle on 2000 175 HP EFI

[Rangman]

Hi to all and hoping someone can help... ****Sorry I have posted this in wrong forum....switching to 2.5 Merc forum****

My Ranger with 2000 175 HP Merc EFI (not opti) has idle water pressure at 10 - 11 PSI.
- Accelerate and can see drop at ~ 12 PSI indicating poppet has opened (although this seems slightly high)
- Continue up to WOT and getting ~ 20 PSI

Model - 1175413WD
Serial - OT148999

It use to have ~ 4 - 5 PSI at idle to my best recollections.

Had new impeller, gaskets and housing last year. After seeing this when I put boat in the water this year, I again replaced just to make sure all good...no change. Have run it a few hours on the lake while going fishing.

The water pressure at idle is steady (but high), not fluctuating as if head gasket etc has small leak.
Engine runs fine
No overheat issues
Replaced water pressure gauge to verify OK, no change and it does drop to 0 when engine off.

*Could one or both stats have crud built up blocking small bleed hole and would this cause excess pressure? Not thinking so as pressure should return to normal as soon as they opened up......I will be replacing stats just to make sure nothing in them and opening correctly. I never idle very far so small possibility one may not be opening correctly "I guess"?????

** Not sure how poppet could effect idle pressure however Merc manual mentions "poppet by-pass" possibly plugged causing over pressure at idle??? I cannot find out if this is a passage in the poppet assembly or where it is, HOPEFULLY someone knows and can advise. I have pieces to rebuild poppet assembly but just not convinced this is issue unless this "by-pass" as mentioned in manual is within the valve.

Have talked with local outboard mechanics and they are unsure and say "better high than low pressure and just run it"......This is not sitting well with me as there is seems possible something is plugged which could cause hot spot within the engine and do not want to hurt it....makes no sense, better to find issue before that happens.

Help, advice, thoughts?????

THX Dave

[JOE54]

it is normal for new pumps to show high check all you can and replace thermos , might do a leak down on cyls for peace of mind , put lil time on it then see if it settles down some , report back

[Rangman]

Thanks Joe. Never seen it this high even with all new pump parts and have probably 10+ hours on it already since replacement.

Good thought on leakdown just to verify. Don't see any "fluctuations" as if pumping into cooling system but worth a look....would have expected an overheat issue also if head gask issue, but with outboards at times never know!

Do you happen to know where the Poppet by-pass is located per mercury manual?

[leonreno]

The poppet valve is on the bottom of the starboard side, usually behind the trim relays. Normally you have to remove or at least lower the bottom cowl to access. Poppet usually only effects above idle pressure. My guess would be thermostats or the pump
just needs to wear in a little.

[Rangman]

Hoping so also....Do you know where "poppet by-pass" is located? I know where the actual poppet valve is but as below exert from Mercury service manual states that "possible causes for over pressure at idle are Plugged poppet by-pass passage or tell tale".

If I am reading this correctly, the manual is not talking about the actual poppet valve but rather a passage or by-pass within the valve or engine block or elsewhere however does not indicate where this is.

I know the tell tale is clear however I am trying to find out if the "poppet by pass" is part of the poppet valve or a passage elsewhere under the poppet in the block or...??

Below in bold is from Mercury service manual>>>

Pressure above 5 psi (34.2kPa)
@ idle....POSSIBLE CAUSE..... •Plugged poppet by-pass passage
or tell-tale

[EuropeanAM]

Before you do ANYTHING else on this, please check this:

Does the water pressure gauge read ZERO when the engine is OFF?

If not, disconnect the hose. Does it read ZERO now?

If not, REPLACE GAUGE.

If above is as it should be, check the gaskets in the poppet valve. One of them tends to "hooch" out and restrict bypass flow. Trim the gasket as shown before assembly:

poppet2-5.jpg

[leonreno]

Before you do ANYTHING else on this, please check this:

Does the water pressure gauge read ZERO when the engine is OFF?

If not, disconnect the hose. Does it read ZERO now?

If not, REPLACE GAUGE.

If above is as it should be, check the gaskets in the poppet valve. One of them tends to "hooch" out and restrict bypass flow. Trim the gasket as shown before assembly:

poppet2-5.jpg

He says in the original post that he changed gauge and it does returns to zero. Hopefully the poppet or thermostats are the culprit if it’s not just from a new pump.

[Rangman]

He says in the original post that he changed gauge and it does returns to zero. Hopefully the poppet or thermostats are the culprit if it’s not just from a new pump.

Yep...gauge is good. I just ordered a proper leak down gauge also so that I have all tools I need hopefully to diagnose further. My plan of attack going forward:
1) Pull stats and verify correct opening and not plugged up.... and have new ones so will replace regardless.
2) Even though running completely normal, I will check spark plug colors, do compression and leak down tests to verify no internal leaks / issues.
3) If no issues with either of these, I will pull poppet assembly and check carefully for any issues or blockages and see if I can figure out what service manual is referring to as "poppet by pass passage" as this is the other item listed in manual as possible cause....will also replace all poppet parts / gaskets as I have them also.
4) will flush when stats and poppet are out to make sure no possibility of mud or silt or something else within system.

Only other thing I can think of as possible could be adapter plate gasket possibly but not really sure how it could increase idle pressure only???

Still open for advice or comments on my plan of attack. Took boat out again tonight and still same high pressure at idle so I am negating possibility of new pump as cause....put too many pumps in this motor over the years and never have seen this. I Generally getting higher WOT pressure but little change normally at idle pressures as very low is normal and how system is designed to operate.

Still hopeful that someone able to identify where the "poppet by-pass passage" per mercury service manual is located for sure!

Thanks to all!

[Rangman]

Before you do ANYTHING else on this, please check this:

Does the water pressure gauge read ZERO when the engine is OFF?

If not, disconnect the hose. Does it read ZERO now

If not, REPLACE GAUGE.

If above is as it should be, check the gaskets in the poppet valve. One of them tends to "hooch" out and restrict bypass flow. Trim the gasket as shown before assembly:

poppet2-5.jpg

Gauge confirmed as good previously. Why does factory gasket require trimming....it has been working as n normal for 18 years as it was??

Thanks for suggestions

Dave

[EuropeanAM]

I agree- most of those gaskets lived happy and healthy for years. What has changed is that the replacement pumps have become a bit more efficient (dimensional migration is likely cause). Higher pressures on the relief circuit likely cause the unsupported area of cork to stretch, and once it begins to get into that passage further the problem progresses on it's own.

[Rangman]

I agree- most of those gaskets lived happy and healthy for years. What has changed is that the replacement pumps have become a bit more efficient (dimensional migration is likely cause). Higher pressures on the relief circuit likely cause the unsupported area of cork to stretch, and once it begins to get into that passage further the problem progresses on it's own.

Could or would this affect idle psi being high if it were partially blocked from this gasket or just high rpm flow affected?

[EuropeanAM]

More likely to cause problems at lower RPM's (idle perhaps up to 2500 or so).

[Rangman]

More likely to cause problems at lower RPM's (idle perhaps up to 2500 or so).

This is within range that I am experiencing issues...TY for the input and I hope to have all necessary parts and tools by next week and stats along with poppet assembly will be my first checks.

[Rangman]

This is within range that I am experiencing issues...TY for the input and I hope to have all necessary parts and tools by next week and stats along with poppet assembly will be my first checks.

UPDATE: Pulled stats and checked them....opening at just over 140 and no obvious debris in either.....replaced as general maintenance anyway.
Did leak down test....all cylinders between 1.5 and ~ 2.5 % so no issues at all here.
Plugs all burning clean and even color
Pulled lower cowling and then Poppet (was most suspected part) and found a load of tiny shell creatures and weeds
poppet.jpg
Cleaned out then replaced gaskets, spring, diaphragm, washer, screw etc.
Ran on muffs and now sitting at ~ 5 PSI at idle.
Will get it back into the water later this week to verify same while on the water. Assuming so far that this has been issue all along which I believe could cause low RPM overheat or hot spots (I did not have overheat but knew something was not right with the high pressure I was seeing at idle) within the engine as this debris would have been reducing by pass flow of water (therefore higher than normal pressure) at lower RPM range. (someone may be able to verify this ??).

[Rangman]

Got a chance to put boat into the lake tonight.

Idle and getting ~ 6 PSI....Idling out canal to lake and telltale good once stats open....accelerate and get pressure drop / poppet opening as expected.....as RPM builds so does water pressure up to ~ 20 PSI at WOT.

All normal again and no worries any longer on cooling issues. THX to all for suggestions / help. Always have done water pumps each year but will now include poppet maintenance a yearly thing now as we live on a shallow and very weedy lake! Will just order spare gaskets to keep in stock.

Dave

[JOE54]

looks real weedy , good for fishes though

[Rangman]

[QUOTE=JOE54;11983154] looks real weedy , good for fishes though[/QUOTE

VERY good for fish! THX Joe