should water rush in ????

[jobie]

started a new post for this issue !!! having overheating problems my question is this. my boat is in the water, today i removed the water intake hose going from the transom assy to my raw water pump ( merc bravo II ). i expected water to rush in but it just trickled in. i put a hose against the fitting that the hose attaches to , i expected the water to blast right through and i would see bubbles comiing up from behind the boat. the water did not appear to flow through as a matter of fact the water was spraying back at me. is it possible to have a blockage somewhere beyond that point ?

 

[dubs283]

Re: should water rush in ????

sounds like the hoses were connected wrong on the pump??

instead of drawing water from the drive, the pump was forcing air back through it

 

[jobie]

Re: should water rush in ????

hoses are on correct and the pump is operating. i pulled the water line where it goes into the heat exchanger and the water was coming up out of the hose about 2-4 inches. boat overheats under load over 2000 rpm. new therostat, circulating pump , raw water pump ( today ). risers are clean with no obstructions , new exhaust flappers. boat is fresh water cooled

 

[TilliamWe]

Re: should water rush in ????

If the end of the hose isn't below the water line, water won't rush in. So that might be perfectly normal in your case.

However, I would think a hose with any kind of water pressure would have been able to blast down through the drive and blow bubbles out those little pickup holes in the side of the drive. After all, it's a straight shot, nothing should be in between those intake holes and your raw water pump.

Where are you located? Do you have zebra mussels?

 

[BigBK]

Re: should water rush in ????

If you put the hose on the fitting where the raw water comes thru the transom you may not see air bubbles because the impellor may be in a position to stop the water flow. and if i am reading this correctly. the water would be coming out of the raw water intake screens in the lower unit.

 

[myoldboat2]

Re: should water rush in ????

the impeller shouldn't be involved because the bravo ii raw water pump is in the bilge and jobie's talking about forcing water through the transom fitting, through the outdrive and out the pickups--no pump in between.

i don't know the bravo ii like i know my older merc drive, but i don't think there's any sort of flapper that should block that flow. even with your boat in the water, you can run the hose through earmuffs and into the lower unit pickups to see if the water shoots through the transom fitting. i suspect it won't. so then youve got a blockage and may need to pull the drive to find it. i had a bad blockage years ago from a shredded impeller from a previous owner. my impeller is in the lower unit and clogged the water pocket outlet in the upper unit. it was a real PIA to find, but it solved the problem that i had paid two mechanics to fix (and they didn't).

i suppose it's possible that at some point someone flushed the raw water pump the wrong way and an old impeller sent pieces that direction. i've read that impellers shouldn't be backflushed because it flips the bend direction and can snap the fin tips off. i don't know if your pump design even allows pieces to move that way. anyway, i doubt this is the problem. more likely your water path is clogged with sand or weeds or something. divide and conquer... keep taking things apart to narrow it down. good luck, hope you find it.

 

[TilliamWe]

Re: should water rush in ????

I agree with myoldboat2, as he explained in greater detail exactly what I was talking about.

 

[BigBK]

Re: should water rush in ????

the impeller shouldn't be involved because the bravo ii raw water pump is in the bilge and jobie's talking about forcing water through the transom fitting, through the outdrive and out the pickups--no pump in between.

i don't know the bravo ii like i know my older merc drive, but i don't think there's any sort of flapper that should block that flow. even with your boat in the water, you can run the hose through earmuffs and into the lower unit pickups to see if the water shoots through the transom fitting. i suspect it won't. so then youve got a blockage and may need to pull the drive to find it. i had a bad blockage years ago from a shredded impeller from a previous owner. my impeller is in the lower unit and clogged the water pocket outlet in the upper unit. it was a real PIA to find, but it solved the problem that i had paid two mechanics to fix (and they didn't).

i suppose it's possible that at some point someone flushed the raw water pump the wrong way and an old impeller sent pieces that direction. i've read that impellers shouldn't be backflushed because it flips the bend direction and can snap the fin tips off. i don't know if your pump design even allows pieces to move that way. anyway, i doubt this is the problem. more likely your water path is clogged with sand or weeds or something. divide and conquer... keep taking things apart to narrow it down. good luck, hope you find it.

Myoldboat2, Thank you for putting me in my place on this one. It will teach me to read a little more careful next time.
I missed that it was a Bravo II. I've gotten use to talking about the Alpha so much I mentaly was thinking Alpha.

Again, Thank You, Bob

 

[jobie]

Re: should water rush in ????

thanks so much for your thoughts and input !!! i bought this boat at an estate auction ( the original owner had passed away ) . so i know no history and i cant call the person i bought it from and ask any questions. its my first fwc cooled boat so i am at a bit of a disadvantage but i am learning alot as i go. as far as mussels i am moored in boston harbor and believe that the boat was moored off cape cod before i got it. i am on vacation next week and will pull the boat and remove the drive and see waht i can find. more food for thought ; when i bought the boat there was a chunck off the skeg busted off , and the trim button did not work!!! if somone pulled this boat out of the water , struck the drive at the ramp and drove it up could a water line have been pinched or broken ?

 

[dvan1901]

Re: should water rush in ????

"when i bought the boat there was a chunck off the skeg busted off , and the trim button did not work!!! if somone pulled this boat out of the water , struck the drive at the ramp and drove it up could a water line have been pinched or broken ?"

Not only that, but the whole lower unit could be damaged and need replacing. If you are comfortable with it, pull the lower unit, look for damage, then pull the whole drive off. Or, take it to a reputable mechanic, give them all the details and have them check it all out for you. It will cost you, but then you know it's all been looked over by someone that does it all the time.

 

[jobie]

Re: should water rush in ????

the drive oil was clean ( changed anyway ) no water or contaminates . i have operated the boat and the drive shifts smoothly , no vibrations. although the motor begins to overheat i have had it at wide open throttle for a few minutes at a time and the drive functions as it should.

 

[myoldboat2]

Re: should water rush in ????

Myoldboat2, Thank you for putting me in my place on this one. It will teach me to read a little more careful next time.
I missed that it was a Bravo II. I've gotten use to talking about the Alpha so much I mentaly was thinking Alpha. Again, Thank You, Bob

oh no, no, no! certainly not putting anyone in their place! i'm generally the one asking the dumb questions here, trying to learn so i don't screw up my old boat. i only wish i had a bravo ii or even an alpha to work on... my late model I sterndrive is 35 years old and still going, knock on wood, knock, knock, knock.

 

[jobie]

Re: should water rush in ????

spoke with someone today that is very familiar with bravo II's. he said that the water line in the transom assy are famous for getting pinched and restricting flow !!! he recommended swapping over to a thru- hull fitting for raw water supply. this weekend i am going to re-plumb my water pump intake hose to the thru-hull fitting for the mascerator i'll let ya know how i make out !!!

 

[TilliamWe]

Re: should water rush in ????

That's not a bad idea. But all Bravos are the same. My dad and I combined have owned 5 Bravo engines (in 4 boats) and put approx 3000 hours combined on them, and never pinched that hose. I am not saying that isn't your problem, but I don't think it's a notorious problem. Maybe ours were restricted, but without closed cooling (except on one engine) we didn't need 100% of the flow that a Bravo pump provides?
I certainly hope it makes your problem go away.

 

[jobie]

Re: should water rush in ????

YA-HOO !!! i moved my raw water intake line to the thru-hull fitting for the mascerator and no more over-heating. that thru-hull fitting is a little small and does not have a scoop and screen on it so i will haul the boat and put the right one on when i get a chance !!! thanks again to all for your thoughts and input