High seawater pressure

[bfernald0]

I ran the engine for 20-30 min and it never went over 125. Next time I will put a thermal gun on the risers and exhaust.

Well, that's evidence against a blockage. Although I agree with the folks on here that high water pressure is generally the result of post pump blockage of some sort. Very odd.

 

[techmitch]

Sounds like you have a blockage some where after the pump.

I ran the engine for 20-30 min and it never went over 125. Next time I will put a thermal gun on the risers and exhaust.

Not over125?

I just re read this post from the beginning. It all started with the raw water pump rebuild. I have never seen a raw water pump all of a sudden increasing pressure exponentially after a rebuild......but I would start there.

Get a replacement pump and put it on the engine. All the advice you have gotten (including mine) is about an after pump blockage. That said....IF the only thing you did was rebuild the pump and it was working fine before.......lets take it out of the equation.

Then if the problem still exists.....you definitely have a after pump blockage (and a spare pump).

Something is amiss here, only 125* after 20-30 min's and high press. doesn't make sense.

 

[PlayDate]

That's why I am going back to the beginning. It makes no sense that a pump rebuild would create this kind of pressure. That said he put an analog gauge on it and sure enough it had a lot of pressure.


As to why he would have cold temps and high pressure.....really goes into the twilight zone. If he hadn't done the analog tests.....I would have believed a few sensor wires got cross connected on the engine.

Just to confirm.....is this your cooling system?

STANDARD COOLING SYSTEM - BRAVO, 7 POINT DRAIN - Serial Range Stern Drive 5.0L MPI ALPHA/BRAVO 0W650000 THRU 1A299999 | Crowley Marine

View parts diagrams and shop online for STANDARD COOLING SYSTEM - BRAVO, 7 POINT DRAIN parts, Serial Range Stern Drive 5.0L MPI ALPHA/BRAVO 0W650000 THRU 1A299999. Offering discount prices on OEM parts for over 50 years. FAST $4.95 shipping available.

www.crowleymarine.com

 

[Schoony]

That's why I am going back to the beginning. It makes no sense that a pump rebuild would create this kind of pressure. That said he put an analog gauge on it and sure enough it had a lot of pressure.


As to why he would have cold temps and high pressure.....really goes into the twilight zone. If he hadn't done the analog tests.....I would have believed a few sensor wires got cross connected on the engine.

Just to confirm.....is this your cooling system?

STANDARD COOLING SYSTEM - BRAVO, 7 POINT DRAIN - Serial Range Stern Drive 5.0L MPI ALPHA/BRAVO 0W650000 THRU 1A299999 | Crowley Marine

View parts diagrams and shop online for STANDARD COOLING SYSTEM - BRAVO, 7 POINT DRAIN parts, Serial Range Stern Drive 5.0L MPI ALPHA/BRAVO 0W650000 THRU 1A299999. Offering discount prices on OEM parts for over 50 years. FAST $4.95 shipping available.

www.crowleymarine.com

Yes, that is my exact cooling system. FYI I have already replaced my raw water pump with a rebuilt so that is now my second new pump. I did notice on the left side where the I did notice starboard side exhaust flats are missing.

 

[Schoony]

Yes, that is my exact cooling system. FYI I have already replaced my raw water pump with a rebuilt so that is now my second new pump. I did notice on the left side where the I did notice starboard side exhaust flats are missing.

Sorry exhaust flappers.

 

[Scott215]

Don't think that would be it . Temp is too low

 

[PlayDate]

Is it possible that you have crossed up the oil pressure switch with the cooling pressure switch? Then everything makes sense. Oil pressure would be around 20 at idle ....40 at cruise. The 2 wire sensors and connectors are really similar.

As to why you aren't getting an oil pressure alarm......it probably is in an acceptable range for Smartcraft.

Your picture of the analog gauge is what disturbs me. Where is it screwed into?

 

[Scott215]

Looks like back of intake normal Chevy oil pressure pick up point can't tell

 

[PlayDate]

Is it possible that you have crossed up the oil pressure switch with the cooling pressure switch? Then everything makes sense. Oil pressure would be around 20 at idle ....40 at cruise. The 2 wire sensors and connectors are really similar.

As to why you aren't getting an oil pressure alarm......it probably is in an acceptable range for Smartcraft.

Your picture of the analog gauge is what disturbs me. Where is it screwed into?

If the analog gauge is screwed into the crossover cooling pipe (item 13 on the Crowley marine chart I posted earlier) on the back of the engine...then it is in the right place.

The sensor connected to the analog gauge tee looks like the correct Mercruiser Raw water Pressure switch.

The two issues I am struggling with is the amount of pressure that is being recorded indicates an almost total blockage of raw water flow.....yet the engine temp is cold. That just doesn't make any sense......at all.

How does the exhaust water look flowing out the flappers? Is it warm and is the volume
the same as it was before the pump change? Based on the pressure readings......you should have almost no water flow at all from the flappers.

If the exhaust water looks normal then it's possible that your analog gauge is way off which could explain the readings we are seeing.

What I am expecting to see on your engine is 1-2 psi at idle and 12-20 at cruise.