nsformula

Hi folks,

1995 Formula 271, 502 efi, Bravo 3. open cooling.

This boat lives on a trailer and I have been having issues burning up the impellor in the belt driven seawater pump.
This setup has a fuel and seawater pump in the same belt driven unit.

As I said the boat is stored on a trailer and I start it on the muffs and hose before leaving home to be sure all is ok.
Probably 3 of the last 5 times it was started it melted the impellor. PIA.
Did my spring start up today after installing as fresh impellor [all merc stuff] and not much water.coming out of the exhaust.
Shut it down and pulled the hoses off the t/stat and filled everything with water.
Started again and temp going up so I turned it off, I haven't checked the pump again but suspect lack of water flow.

The muffs I am using do not seal really tight on the drive, a lot of water is blowing out around the muffs but I assume the system should pick up the water flow once the engine is running.

http://thumbs2.ebaystatic.com/d/l225...ATOkhvInkQ.jpg

http://www.chmarine.com/acatalog/mot...dual-flush.jpg

How does this system work, do I need positive pressure from the muff thru the drive to start the water flow or will the drive pick up water flow.
Is there a pump in the drive to prime the system.

If there is no prime pump in the drive, could be as simple as needing better muffs.

Any feedback appreciated

3pointstar

I have the exact same muff's- with a Bravo 3. I NEVER had any issue. I have placed the "cups" around the intake holes so as to get as good a seal as possible. Also, I don't open the water valve WOT- but that depends on your water pressure. Are you sure that you are using a hose with enough volume. I know some of the smaller diameter may not be providing enough water. In addition, I have NEVER revved the engine on muffs -- strictly an idle. If you are consistently burning up an impeller - without sounding condescending-- I am not an mechanic but--
a) are you sure you are putting the impeller in correctly and that the housing isn't scored or damaged?
b) are the intake (water into the pump) in the correct orientation-- in other words is the water in hose in the right location on the housing. I not 100% sure but I believe the bottom hose is the water in side - but PLEASE verify this with an expert.

I hope some of this helps and please post any outcome

all the best

3pointstar

Cole2534

iTrader: (1)

My bravo WILL NOT run on the muffs. Go to home depot and you can buy 1-1/4" hose and fittings to tie the pump directly to pump suction.

mike tkach

iTrader: (3)

the sea pump will suck more water than the average garden hose can flow even at idle.it does not take much above idle to burn up the impeller.

motor

iTrader: (3)

When you have muffs on the drive and crank the engine ,pretty much all the water flowing out around edges of muffs should stop .Sometimes on initial startup it take a quick blip of the throttle to prime the pump. If water keeps falling out from around the muffs you haven't picked up chit. A good pump and muffs sealed tight will suck a typical garden hose dry at anything above idle

bonesmalon

iTrader: (1)

X2 hose is just good enough to fire it and give you confidence it's ready to go. Anything more needs to be dunked.

BUP

iTrader: (9)

the black plastic housing is scored / grooved internally causing the impeller to cavitate - Always install new housing with impeller - these black housing can groove very easily or even burn grooves into them. Also sand kills them along with impeller.

If you did not drain your impeller housing during winterization it could very well have distorted and or cracked the bridges interally in the housing from freeze damage.

I understand you have mid 90s app here but did someone change the outdrive out with duel water pickups ? Side water picks and low water picks ?

What brand impellers are you installing ?

When you install the impeller what type of lube did you put on it. Grease and or oil is HIGHLY NOT recommended, Do NOT use these products.

did you properly install all o ring gaskets and properly torqued the bolts for the impeller housing. keep in mind it only requires 10 lbs of torque and that's it .Also torque in a 3 pass star pattern. Too much torque will crack these housing or distort them.

Next you can take of the water inlet hose engine compartment transom side or take it off at the impeller housing and install your own 3 to 4 foot hose, then shove the water garden house into that and hose clamp it off, Turn water on and start pronto. does it pump water then ? If not you have something wrong or damage impeller / or housing or both.

lastly when you turn the water on using the muffs - sometimes the water pressure will slide away the muffs from the intake inlets causing the impeller to suck a bunch air. hence no water flow or not enough water flow. With that said damage can occur to the housing and impeller.

I highly recommend these muffs for all Mercruiser drives with side water intake inlets. Been using them from day one NEVER had a problem especially sliding away form the water intake inlets. Good luck and link below. I tried to cover the gamit about the possible problem(s)

http://www.ebay.com/itm/Genuine-Merc...-/201261199733

BUP

iTrader: (9)

forgot loose belt (improper tension) or stretched belt for the impeller housing pulley. One that gets missed often

TWIN-SPINS

I have seen the suction of the sea pump ,,,collapse the garden garden hose at idle

BUP

iTrader: (9)

that's why you use a industrial contractor grade heavy wall garden hose, not the type that you water the lawn with. I have never sucked a garden hosed flat no matter of the boat app even at higher rpms running for x amount time. You have cover all your bases if you are going to work on your own boats and that includes the small stuff. Just saying..