Unusual Bravo raw water pump problem

[elpaso]

Sea Ray 24 1999 5.7 Merc Bravo I outdrive, raw water cooled, salt water. Total hours 260. Always on boat lift. Flushed after every use. <br /> Problem - Engine overheat, found impeller in pieces, as if run dry. <br />Replaced impeller - o ring and wear plate - housing looked like new, bearing smooth, no<br />sign of leaking. Replaced T-stat 140* Engine still running hot. <br />Pulled inlet hose at t-stat housing - at idle good flow of water - raise rpm to 1600 -<br />water flow totalily stops for 6-8 seconds - then resumes at less flow than idle. <br /><br />Replaced pickup hose from pump to transom, thinking possible interior declamation <br />problem with suction. Checked outdrive hose for crimped hose - looks good.<br />Have back flushed everything - same flow problem - same overheat.<br />What am I missing ?

 

[Don S]

Re: Unusual Bravo raw water pump problem

Did this happen just after any repairs to the cooling system, or just went from good to bad all of a sudden?

 

[QC]

Re: Unusual Bravo raw water pump problem

Could the impeller be spinning on the shaft? Or the pulley?

 

[elpaso]

Re: Unusual Bravo raw water pump problem

Don - No repairs to anything in 1 year, boat had set on lift for 5 months never started.<br />2nd question - impeller shaft is turning - impeller shaft flat - 1 side - impeller<br />has to turn. No possibly of slippage.<br />Thank you for quick replies.

 

[Don S]

Re: Unusual Bravo raw water pump problem

I would look at the impeller again. It has either a plastic or metal bushing that goes over the pump shaft. IF that bushing is slipping inside the impeller, then it's not turning the impeller at higher speeds.<br />Once you take the pump apart, put the impeller on the shaft and see if you can turn the impeller while holding the pulley (Shaft)

 

[elpaso]

Re: Unusual Bravo raw water pump problem

Don - I will do so first thing in the<br />morning - again - thanks for quick reply

 

[Bondo]

Re: Unusual Bravo raw water pump problem

Did you find ALL of the Pieces of the Trashed Impeller,..???.....<br /><br />If only 1 little piece was Missed,...... It could be getting lodged somewhere causing this Issue.......

 

[Don S]

Re: Unusual Bravo raw water pump problem

Bondo brings up a good point. If you didn't find all the pieces, look in the power steering pump cooler. It's located between the raw water pump and the thermostat housing. If it's the tube bundle type and not the full flow type cooler, the end is probably packed full of impeller pieces. Then when at idle you get a little flow of water, when you speed it up, more pressure packs the pieces into the cooler even tighter and the flow stops.

 

[elpaso]

Re: Unusual Bravo raw water pump problem

I found all pieces of impeller - have back flushed oil cooler - all hoses and from<br />pump to outdrive, 3 times<br /><br />Today I checked impeller for slippage, there was none. Just to be sure I installed new<br />impeller- wear plate and housing.<br />. <br />Started engine - same problem. Pulled discharge hose from pump, and ran engine.<br />Not going through oil cooler.<br />At idle normal flow - as rpm goes to 1700 flow stops for 3-5 seconds- starts again<br />and continues at about the same as idle. <br /><br />Boat was fresh water for 5 years 2 years salt - always on lift. Bell housing<br />water hose is not kinked - looks like new. Everything looks as a 1 year old boat.

 

[QC]

Re: Unusual Bravo raw water pump problem

Seems like you have confined this to the supply side unless that pulley is slipping.<br /><br />You are performing these tests in the water, right? No muffs?

 

[elpaso]

Re: Unusual Bravo raw water pump problem

Every test in the water - belt is tight <br />no slipping - every thing normal - no noise-<br />no leaking - but pump not pumping

 

[QC]

Re: Unusual Bravo raw water pump problem

Could you put it on muffs and see if you have good flow to the pump inlet via pressure?

 

[elpaso]

Re: Unusual Bravo raw water pump problem

I did try with muffs - but water pressure <br />is low at dock, well water not normal city<br />pressure - saw no big change. At higher rpm<br />maybe less flow ?

 

[tommays]

Re: Unusual Bravo raw water pump problem

i think its time for some clear water hose like i have seen newport dave use <br /><br /><br />i fix a lot of different types of pumps and if the inpeller is turning you gotta be sucking air or have a blockage you cant see ?<br /><br /><br />tommays

 

[elpaso]

Re: Unusual Bravo raw water pump problem

The bell housing water hose looks good, no kinks, but can it delaminate internally, and cause a blockage ?

 

[Don S]

Re: Unusual Bravo raw water pump problem

It could, you could also have an air leak in the hose that goes through the transom or the elbow that bolts on the inside. It would be high enough to allow air to suck in while running because it may be out of the water. But I would suspect a blockage as a hole would be more of a problem at low rpm, not just high rpm where it stops completely.<br />You are just going to have physically check each item from the openings in the drive to the pump and find out what is blocked. Could be anything.

 

[I/O WALDO]

Re: Unusual Bravo raw water pump problem

Don't know if this the solution,but I once had a complaint about an above idle temp problem(95,b1) and EVENTUALLY found that the rubber sleeve around the water inlet tube going through the transom housing had migrated foward and had closed down around the tube to about diameter of about 1/4"!When I removed the elbow from the transom housing where the inlet hose to the pump connects I found the restriction!Strange butt true!