Alpha 1 gen 2 5.7L overheating

[mrjamieson]

Running a Merc outdrive in a bucket of water usually doesn't work out well. The pump needs to be fully submerged, and that is tough to do. Those pumps can not pull water, they have an open vent air bleed port to prime them - meaning they prime by submersion. Mostly they get burned up when attempting to run in a bucket.

If you do not have enough water pressure/flow to run on muffs at wherever you are working on the boat you need to fix that. Go somewhere else or improve your hose flow - that's the lesson.

 

[Scott Danforth]

Update. I installed an OEM impeller. SAME PROBLEM. I then matched the new Sierra temp. gauge with a Sierra sender. NO teflon tape this time. Better results but still ran hotter than I like. Built a container to submerge the outdrive and ran it. Everything looks good. The gauge never went over 170 from idle to 1000 rpm. Eventhough the old engine ran fine on muffs, this one will not. Lesson learned. Forget muffs! Thanks Achris and everyone who took time to respond.

Unless the container was big enough to have the whole drive submerged so the impeller starts out 5-8" below the water surface, it wont prime and you will burn up the impeller.

always use muffs and always make sure the hose is 5/8" or 3/4" and the spigot is on full. there should be a 10' spray from the muffs until the motor starts.

 

[mrjamieson]

The hose and new muffs are the same I used on the old engine. I'm confused about the submersion. If the muffs supply water to the inlet holes, why can't you use my 50 gallon trough which supplies water up to the trim pistons. The gauge used to climb to 200' and had marginal discharge. Now, the exhaust discharge is great/high volume.

 

[mrjamieson]

Running a Merc outdrive in a bucket of water usually doesn't work out well. The pump needs to be fully submerged, and that is tough to do. Those pumps can not pull water, they have an open vent air bleed port to prime them - meaning they prime by submersion. Mostly they get burned up when attempting to run in a bucket.

If you do not have enough water pressure/flow to run on muffs at wherever you are working on the boat you need to fix that. Go somewhere else or improve your hose flow - that's the lesson.

How is the pump fully submerged on muffs?

 

[Scott Danforth]

How is the pump fully submerged on muffs?

its not, however water is forced to the impeller to force a prime. that is how muffs work on a 60PSI+ residential water supply.

 

[Scott Danforth]

The hose and new muffs are the same I used on the old engine. I'm confused about the submersion. If the muffs supply water to the inlet holes, why can't you use my 50 gallon trough which supplies water up to the trim pistons. The gauge used to climb to 200' and had marginal discharge. Now, the exhaust discharge is great/high volume.

because the impeller is a full 8" above the water inlet and the impeller will burn itself up and the housing up before it primes.

 

[mrjamieson]

because the impeller is a full 8" above the water inlet and the impeller will burn itself up and the housing up before it primes.

 

[mrjamieson]

I ran it like that for about 20 mins. Should I replace the impeller and housing again?

 

[Rick Stephens]

I ran it like that for about 20 mins. Should I replace the impeller and housing again?

Probably should inspect it, in the least.

 

[mrjamieson]

Unless the container was big enough to have the whole drive submerged so the impeller starts out 5-8" below the water surface, it wont prime and you will burn up the impeller.

always use muffs and always make sure the hose is 5/8" or 3/4" and the spigot is on full. there should be a 10' spray from the muffs until the motor starts.

A 10ft spray out of the muffs or hose???

 

[Scott Danforth]

A 10ft spray out of the muffs or hose???

the muffs will spray 10 feet in all directions when the hose is on full until the engine is started. water has to go somewhere

 

[mrjamieson]

the muffs will spray 10 feet in all directions when the hose is on full until the engine is started. water has to go somewhere

I'll have to get a pair of new muffs because mine don't spray anywhere near 10ft. Been in the same house for 30+ years and the water pressure is fine. When the outdrive was in the trough (a mistake I won't repeat) the intake hose at the t-stat was solid, only 140' at the sender. On the muffs you can feel it pulsing through the hose. The muffs leak almost as much water than what comes out of the exhaust ports. (the muffs are only a year old) If the new muffs still leak on the outdrive, I'll try same sort of a way to get them more secure.

 

[Bondo]

I'll have to get a pair of new muffs because mine don't spray anywhere near 10ft. Been in the same house for 30+ years and the water pressure is fine. When the outdrive was in the trough (a mistake I won't repeat) the intake hose at the t-stat was solid, only 140' at the sender. On the muffs you can feel it pulsing through the hose. The muffs leak almost as much water than what comes out of the exhaust ports. (the muffs are only a year old) If the new muffs still leak on the outdrive, I'll try same sort of a way to get them more secure.

Ayuh,..... Donno what you've got for a trough, but if the water level is all the way up to the trim cylinders,.....
That's Ok, as the water pump is at 'bout the same level,......

Most troughs/ tanks can barely get the water level to cover the water pick up holes, which is Not high enough, which will burn up the impeller,.....

 

[Lou C]

Some of the muffs being sold, are made of rubber too stiff to conform to the lower unit, to get enough water in. I had this with the dual feed rectangular Tempo style muffs. The best ones I have used are the Merc/Quicksilver ones with the metal clamp. They are softer rubber and confirm to the shape of the lower unit.

 

[mrjamieson]

Ayuh,..... Donno what you've got for a trough, but if the water level is all the way up to the trim cylinders,.....
That's Ok, as the water pump is at 'bout the same level,......

Most troughs/ tanks can barely get the water level to cover the water pick up holes, which is Not high enough, which will burn up the impeller,.....

Well that makes me feel better. The water goes right to the bottom of the cylinders and the exhaust flow out the transom assy. is 3 times greater than the muffs.

 

[achris]

.... The gauge never went over 170 from idle to 1000 rpm. ...

This is a calibrated gauge? If it's the dash gauge, it's not calibrated, and can have as much as a 25% error. Get yourself an IR gun if you want accurate results....

Chris.....

 

[mrjamieson]

This is a calibrated gauge? If it's the dash gauge, it's not calibrated, and can have as much as a 25% error. Get yourself an IR gun if you want accurate results....

Chris.....

Chris, I replaced all the dash gauges this winter with a new Sierra set. (fuel, temp, oil, mph, tach, trim, volt, etc ..) In turn I made sure the new oil and temp senders were Sierra as well. I did use an IR gun. The temp gauge read approx 170' and the outside of the temp sender (in the t-stat housing) stayed steady at 140' The top of both risers were just warm and all the hoses were in the normal range. Nothing was very hot except for the manifolds. I think you're correct. I believe the gauge just read higher than the actual temp.

 

[nola mike]

I'll have to get a pair of new muffs because mine don't spray anywhere near 10ft. .

@Scott Danforth sometimes exaggerates about size... I'll say mine sprays out a solid 8 inches though

 

[achris]

@Scott Danforth sometimes exaggerates about size... I'll say mine sprays out a solid 8 inches though

@Scott Danforth ALWAYS exaggerates about size.

(I'm just happy with my 5-1/2 inches)

Chris.....

 

[Rick Stephens]

@Scott Danforth ALWAYS exaggerates about size.

(I'm just happy with my 5-1/2 inches)

Chris.....

I'm feeling pretty weak here.