Sharing fresh water intake from one engine to a second engine

[pachanga58]

Here's is an unique question, at least for me. I searched the forums, did not see this question in the forums.
Boat - 1989 Sea Ray Pachanga, 27ft. Twin 5.7 Mercruisers. Alpha drives. about 750 hours on each motor. Exhaust through water lift mufflers through the hull, not through the props. The eight cylinders feed into a single exhaust for each motor. on the lake, Port motor started showing a higher than normal temperature - 200 degrees rather than 145 degree while idling through a no-wake zone. the starboard motor temperature was right on the money 145 degrees. I shut the port engine down. Once out of the no-wake zone, I restarted the port motor and accelerated to plane speed. Port motor temperature came down to approximately 150 degrees, but not the 145 that I expect it to be. Watched it closely... powered down and once the boat fell off of plane , the temperature on the port side started rising. so I decided to shut the motor off again and just sort of go real slow back to home. The starboard motor will not bring this boat back on plane. Now, get home, pulled the boat out of the water, and hooked up muffs on the starboard motor and all was good - temperature was 145 degrees - good water flow out the exhaust. Hooked up the Port motor. No water flow other than a few drops out the port motor exhaust at 800RPM. Obviously the same effect - temperature started rising quickly - shut the motor off at 180 degrees. Looking at the flowchart for a raw water diagram to the cooling system, the inlet water that would be picked up in the outdrive is routed through the oil/power steering cooler and on to the inlet (lower right) on the thermostat housing. I am thinking that very possibly that the impeller in the outdrive is not during its job anymore and needs to be replaced- however, I also have always thought that on plane, water is not being pumped up (per se) by the impeller but the intake on the outdrive provides the water to the motor by water pressure from the water flowing over the intakes on the drive when on plane. Is that a true statement or not? As is, the motor temps only go high when at idle. On plane the temps are 5 degrees higher that the starboard motor. Now for the crazy question. If I were to put a tee into the starboard motor's intake of the water from the lake that goes to the intake of the thermostat housing, and use the water that is being pumped by the starboard motor to supply the port motor's thermostat housing and thus provide water water to the port moto's water pump - will the starboard engine provide enough water at idle to cool the port motor sufficiently? a crazy question, but there is a couple of reasons... one, I will have the impeller in the port motor' outdrive replaced, but I just am curious as hell if this may give the port motor enough water to cool it. I am thinking if this works - I may have to work me out a "kit" if this every happens again and I get back to the slip in a reasonable amount of time instead of slowly idling back for 5 miles and taking hours.
of course - this is one of the "No. don't do that" - I figure you guys will let me know in so many ways.

 

[poconojoe]

I'm going to tag along to see what the experts might say.

But, for me, I wouldn't do it.
It might cause the good flowing engine to starve for cool water.

It is by far more detrimental for marine engines when they overheat than it is for our land vehicles. And damage can happen real fast, within seconds.

You can melt exhaust shutters and their metal parts can drop down and cause blockage.

Anything rubber in the exhaust can melt.

So much else can go wrong. It's not worth the chance.

I would change the impeller in both drives. They don't cost much, not hard to do and good peace of mind. Plus, you'll have a record of when both of them were changed.

 

[tpenfield]

Thanks for asking the question . . .

My comments.

The Port outdrive impeller is probably worn, but not highly damaged, so it is able to pump sufficient water when the RPM's are up and the boat is at speed.

Some truth to the idea that the pressure around the outdrive while at cruising speed is providing some water pressure . . . although who knows how much

Connecting the systems together probably won't really work well. If you loose raw water pressure on one of the engines (ex. failed impeller), then water will probably flow from the good outdrive to the bad outdrive and not even go along the path to the engine(s). Keep in mind water will flow from high pressure to low pressure.

You are best to fix the worn impeller (or possibly you just have a clog at the oil cooler and the impeller is actually fine). Check that out too.

 

[Bondo]

Ayuh,...... Welcome Aboard,...... Seems it would be awhole lot easier to just service the drives regularly, so the impeller isn't run til it fails,....
Than to build a jury-rig kit, that may, or may not work,....

I'm thinkin' that the bits from the broken impeller are probably restrictin' the water flow at speed,....

 

[Lou C]

That bit of water pressure from the drive moving forward, is not going to push water up 18" and forward approx 30" so that the water enters the thermostat housing. All you need to do is service the impellers approx every 3 seasons, or sooner of local conditions dictate it.

 

[Scott06]

You’re doing a lot of thinking about a work around…. but not starting with the basics replace impellers and housings with oem units, backflush to make sure any impeller pieces are not blocking anything, inspect your exhaust manifolds and elbows, make sure thermostats are in good shape and you won’t have any issues

Keep up with that maintenance and you won’t have issues down the road

 

[QBhoy]

No. Water will flow to the path of least resistance. Be amazed if it worked well.

 

[pachanga58]

Thanks for asking the question . . .

My comments.

The Port outdrive impeller is probably worn, but not highly damaged, so it is able to pump sufficient water when the RPM's are up and the boat is at speed.

Some truth to the idea that the pressure around the outdrive while at cruising speed is providing some water pressure . . . although who knows how much

Connecting the systems together probably won't really work well. If you loose raw water pressure on one of the engines (ex. failed impeller), then water will probably flow from the good outdrive to the bad outdrive and not even go along the path to the engine(s). Keep in mind water will flow from high pressure to low pressure.

You are best to fix the worn impeller (or possibly you just have a clog at the oil cooler and the impeller is actually fine). Check that out too.

I do replace replace the impellers every 2 years - I have gone 3 years - the question for me was in an emergency - could the single impeller feed two motors. After some experimenting last night - the answer for me is no BUT you guys are absolutely correct. First line of maintenance is replace the impeller if at all any doubt FIRST. After some experimenting last night, the single engine impeller will not provide enough water overall to work for both motors. I first unhooked the hose to the thermostat manifold to make sure I was actually getting water flow through the outdrive and through the oil cooler via a muff with a low volume of water from the water hose.. Cranked the motor and in less than 5 seconds there was a very nice volume of water coming out. Now that really doesn't tell me much as even with the low pressure on muffs, the impeller could be worn. However, me being the

Here's is an unique question, at least for me. I searched the forums, did not see this question in the forums.
Boat - 1989 Sea Ray Pachanga, 27ft. Twin 5.7 Mercruisers. Alpha drives. about 750 hours on each motor. Exhaust through water lift mufflers through the hull, not through the props. The eight cylinders feed into a single exhaust for each motor. on the lake, Port motor started showing a higher than normal temperature - 200 degrees rather than 145 degree while idling through a no-wake zone. the starboard motor temperature was right on the money 145 degrees. I shut the port engine down. Once out of the no-wake zone, I restarted the port motor and accelerated to plane speed. Port motor temperature came down to approximately 150 degrees, but not the 145 that I expect it to be. Watched it closely... powered down and once the boat fell off of plane , the temperature on the port side started rising. so I decided to shut the motor off again and just sort of go real slow back to home. The starboard motor will not bring this boat back on plane. Now, get home, pulled the boat out of the water, and hooked up muffs on the starboard motor and all was good - temperature was 145 degrees - good water flow out the exhaust. Hooked up the Port motor. No water flow other than a few drops out the port motor exhaust at 800RPM. Obviously the same effect - temperature started rising quickly - shut the motor off at 180 degrees. Looking at the flowchart for a raw water diagram to the cooling system, the inlet water that would be picked up in the outdrive is routed through the oil/power steering cooler and on to the inlet (lower right) on the thermostat housing. I am thinking that very possibly that the impeller in the outdrive is not during its job anymore and needs to be replaced- however, I also have always thought that on plane, water is not being pumped up (per se) by the impeller but the intake on the outdrive provides the water to the motor by water pressure from the water flowing over the intakes on the drive when on plane. Is that a true statement or not? As is, the motor temps only go high when at idle. On plane the temps are 5 degrees higher that the starboard motor. Now for the crazy question. If I were to put a tee into the starboard motor's intake of the water from the lake that goes to the intake of the thermostat housing, and use the water that is being pumped by the starboard motor to supply the port motor's thermostat housing and thus provide water water to the port moto's water pump - will the starboard engine provide enough water at idle to cool the port motor sufficiently? a crazy question, but there is a couple of reasons... one, I will have the impeller in the port motor' outdrive replaced, but I just am curious as hell if this may give the port motor enough water to cool it. I am thinking if this works - I may have to work me out a "kit" if this every happens again and I get back to the slip in a reasonable amount of time instead of slowly idling back for 5 miles and taking hours.
of course - this is one of the "No. don't do that" - I figure you guys will let me know in so many ways.

I'm going to tag along to see what the experts might say.

But, for me, I wouldn't do it.
It might cause the good flowing engine to starve for cool water.

It is by far more detrimental for marine engines when they overheat than it is for our land vehicles. And damage can happen real fast, within seconds.

You can melt exhaust shutters and their metal parts can drop down and cause blockage.

Anything rubber in the exhaust can melt.

So much else can go wrong. It's not worth the chance.

I would change the impeller in both drives. They don't cost much, not hard to do and good peace of mind. Plus, you'll have a record of when both of them were changed.

I do replace replace the impellers every 2 years - I have gone 3 years - the question for me - was that - in an emergency - could the single impeller feed two motors. After some experimenting last night - the answer for me is no. BUT you guys are absolutely correct. First line of maintenance is replace the impeller if at all any doubt FIRST. After some experimenting last night, the single engine impeller will not provide enough water overall to work for both motors. I first unhooked the hose to the thermostat manifold to make sure I was actually getting water flow through the outdrive and through the oil cooler via a muff with a low volume of water from the water hose.. Cranked the motor and in less than 5 seconds there was a decent volume of water coming out. Now that really doesn't tell me much as even with the low pressure on muffs, the impeller could be worn. Now me being the ..hmmm... experimental person I am, I put a tee fitting in to the intake hose off the starboard motor and fed the water from it into the intake on the port motor. now - one thing I did notice, the starboard motor was pumping a noticeable amount more water than the port motor. as in .. I got a LOT of water on the starboard motor. Cranked both motors and at 800 RPM, both motors were sitting at 155 degrees, whereas on a single feed, the motors would be at 145 on a normal setup - each motor being fed by it's own impeller . I turned down the water pressure on the hose to try to mimic the outdrives sitting in the lake. Some more experimenting and it was obvious that the impeller on the port motor was definitely not performing 100%. The water out the exhaust of both motors at 800 rpm, was flowing almost the same - I just used a 5 gallon bucket to catch the water out. however, dropping the idle to 600 rpm, big difference, not near the same amount of water over 3 minutes. With that done, I decided to change the port impeller and while it "looked good", it was definitely worn compared to the new one. Once installed, and checking the water flow again (the intake side of the thermostat manifold, the volume of water flowing was just like the starboard motor. so - as you guys said - any doubt - start with the impellers FIRST. and as someone pointed out - running two motors on one source of water , if that impeller fails - good chance both motors will be damaged. Thanks again for the discussion. Was very informative. I have had this boat for 15 years now and the 5.7 motors have been rock solid and I also learned a lot from working on this boat myself. Simple and easy to work on.

 

[pachanga58]

Here's is an unique question, at least for me. I searched the forums, did not see this question in the forums.
Boat - 1989 Sea Ray Pachanga, 27ft. Twin 5.7 Mercruisers. Alpha drives. about 750 hours on each motor. Exhaust through water lift mufflers through the hull, not through the props. The eight cylinders feed into a single exhaust for each motor. on the lake, Port motor started showing a higher than normal temperature - 200 degrees rather than 145 degree while idling through a no-wake zone. the starboard motor temperature was right on the money 145 degrees. I shut the port engine down. Once out of the no-wake zone, I restarted the port motor and accelerated to plane speed. Port motor temperature came down to approximately 150 degrees, but not the 145 that I expect it to be. Watched it closely... powered down and once the boat fell off of plane , the temperature on the port side started rising. so I decided to shut the motor off again and just sort of go real slow back to home. The starboard motor will not bring this boat back on plane. Now, get home, pulled the boat out of the water, and hooked up muffs on the starboard motor and all was good - temperature was 145 degrees - good water flow out the exhaust. Hooked up the Port motor. No water flow other than a few drops out the port motor exhaust at 800RPM. Obviously the same effect - temperature started rising quickly - shut the motor off at 180 degrees. Looking at the flowchart for a raw water diagram to the cooling system, the inlet water that would be picked up in the outdrive is routed through the oil/power steering cooler and on to the inlet (lower right) on the thermostat housing. I am thinking that very possibly that the impeller in the outdrive is not during its job anymore and needs to be replaced- however, I also have always thought that on plane, water is not being pumped up (per se) by the impeller but the intake on the outdrive provides the water to the motor by water pressure from the water flowing over the intakes on the drive when on plane. Is that a true statement or not? As is, the motor temps only go high when at idle. On plane the temps are 5 degrees higher that the starboard motor. Now for the crazy question. If I were to put a tee into the starboard motor's intake of the water from the lake that goes to the intake of the thermostat housing, and use the water that is being pumped by the starboard motor to supply the port motor's thermostat housing and thus provide water water to the port moto's water pump - will the starboard engine provide enough water at idle to cool the port motor sufficiently? a crazy question, but there is a couple of reasons... one, I will have the impeller in the port motor' outdrive replaced, but I just am curious as hell if this may give the port motor enough water to cool it. I am thinking if this works - I may have to work me out a "kit" if this every happens again and I get back to the slip in a reasonable amount of time instead of slowly idling back for 5 miles and taking hours.
of course - this is one of the "No. don't do that" - I figure you guys will let me know in so many ways.

I posted an update. However - one update did not make it correctly and had to repeat it. My apologies for the messed up update.

 

[poconojoe]

Just for the record, I think you're playing with fire. Just my opinion though.

Playing around with engine cooling is just too risky.
So much damage can occur in such a short time.

One thing in particular, lowering the volume of the hose feeding the muffs is a bad idea.
The pressure of most garden hoses is barely adequate as it is.

I hope you're not running both engines with the same hose at the same time.

Again, my opinion. Call me wrong or over cautious, but I wouldn't play games with my engine cooling system.

 

[pachanga58]

Just for the record, I think you're playing with fire. Just my opinion though.

Playing around with engine cooling is just too risky.
So much damage can occur in such a short time.

One thing in particular, lowering the volume of the hose feeding the muffs is a bad idea.
The pressure of most garden hoses is barely adequate as it is.

I hope you're not running both engines with the same hose at the same time.

Again, my opinion. Call me wrong or over cautious, but I wouldn't play games with my engine cooling system.

I agree with you. I get to thinking a lot of "What if I do this" stuff and away I go. I do it with extreme caution so I don't stress and hurt the motors and also don't hurt myself So I listened to the vast knowledge that is here on the forum and made the right choice. But I do agree with you and the others whom said.... ahhh,,, yea ..that ain't a good idea and it will not work. Thank for the reply,

 

[poconojoe]

I agree with you. I get to thinking a lot of "What if I do this" stuff and away I go. I do it with extreme caution so I don't stress and hurt the motors and also don't hurt myself So I listened to the vast knowledge that is here on the forum and made the right choice. But I do agree with you and the others whom said.... ahhh,,, yea ..that ain't a good idea and it will not work. Thank for the reply,

I get that.
Keeping your mind active, questioning how things operate, etc. is better than just sitting around oblivious to everything around you.
A lot of the times you need hands on to gain knowledge. I think I've learned more in life by tinkering with things rather than reading about them.

I guess as long as you keep a good eye on the temperature gauge you should ok. If you see it head up too high and shut it down right away, you should be ok. That also depends on if you can trust your temperature gauge. Many boat gauges are a bit untrustworthy.

 

[Scott06]

I agree with you. I get to thinking a lot of "What if I do this" stuff and away I go. I do it with extreme caution so I don't stress and hurt the motors and also don't hurt myself So I listened to the vast knowledge that is here on the forum and made the right choice. But I do agree with you and the others whom said.... ahhh,,, yea ..that ain't a good idea and it will not work. Thank for the reply,

Are you using OEM merc impellers or aftermarket ? I know the gen one impellers don’t last as long but I was getting at least 5-6 years on mine back in the day.

If you have a pic of you boat post it I’m on my second sea Ray and always liked the Pachengas

 

[pachanga58]

Hopefully it is ok to insert three photos here as you asked. it's an 1989 Pachanga 27. Very original. Power is twin carbed 5.7Ls with Alpha outdrives. Have to overlook that my trim gauges do not work. I have so many hours in this boat I know where the tabs and trim is at without looking at the gauges. same with how the motors are running in sync, they have an unique sound when both are working together. The Pachanga is a heavy boat overall but the twin 350 mags can push it to roughly 53MPH at WOT. I typically just run at 4000 RPM if the lake is clear of traffic. this is not a GPS speedometer but the old style pitot. Lake Murray in SC has gotten very crowded in the last couple of years so I have to watch for slower traffic, especially pontoons. Overall- very stable and can carve its way though rough water.

 

[pachanga58]

I use the OEM Mercury kits. I keep two on hand.

 

[Scott06]

I use the OEM Mercury kits. I keep two on hand.

Nice boat.

Just wanted to make sure you were using OEM, generally they last the longest.

 

[Bondo]

Ayuh,..... Anybody else heard of Globe Impellers,..??
The blue impellers,....

I put one in my ole tin fishin' barge, 4.3LX- Alpha 1,....
Ran it 10 years or more, 'n it was still pumpin' just fine, when I pulled the driveline, 'n junked the barge,.....

 

[pachanga58]

Ayuh,..... Anybody else heard of Globe Impellers,..??
The blue impellers,....

I put one in my ole tin fishin' barge, 4.3LX- Alpha 1,....
Ran it 10 years or more, 'n it was still pumpin' just fine, when I pulled the driveline, 'n junked the barge,.....

I can't say I have heard of them. I usually stick with what has always worked for me on anything but I may take a look at that brand. I have a 88 Sea Ray with a 4.3l in it and I will be changing the impeller on it soon. Edit - just looked them up... the Run_Dry one is a little on the high side but that run dry capability looks interesting.

 

[Scott06]

Ayuh,..... Anybody else heard of Globe Impellers,..??
The blue impellers,....

I put one in my ole tin fishin' barge, 4.3LX- Alpha 1,....
Ran it 10 years or more, 'n it was still pumpin' just fine, when I pulled the driveline, 'n junked the barge,.....

Gen one or two?i just changed an oem out of my gen two after 6 years looked essentially new..

 

[Bondo]

Ayuh,.... Gen.I