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260 Merc heating up on idle

tuna_man

tuna_man

Regular Contributor
Hi Guys

I noticed temp going close to offscale when idling (floating).

It was also idling a bit low, 500RPM.

As soon as I increased to 1000 RPM temp quickly droppped to normal, & operated perfect rest of day. (on the move).

Tonight I checked the check valves at top of thermostat housing, (inside elbow cooling hoses) looked perfect, balls sealing well, good spring pressure. (Ive got the old style brass tee fitting, no corrosion).

I adj the idle to 650, but still started to warm up unless I increased to 1000.

Was it the low idle or could it be another issue?

Impellor & pump new 5 yrs ago, (300hrs ago)

1988 260 Alpha1, SaltWC, 350 SBC.
 
tuna_man said:
Hi Guys

I noticed temp going close to offscale when idling (floating).

It was also idling a bit low, 500RPM.

As soon as I increased to 1000 RPM temp quickly droppped to normal, & operated perfect rest of day. (on the move).

Tonight I checked the check valves at top of thermostat housing, (inside elbow cooling hoses) looked perfect, balls sealing well, good spring pressure. (Ive got the old style brass tee fitting, no corrosion).

I adj the idle to 650, but still started to warm up unless I increased to 1000.

Was it the low idle or could it be another issue?

Impellor & pump new 5 yrs ago, (300hrs ago)

1988 260 Alpha1, SaltWC, 350 SBC.
Click to expand...

Ayuh,.... Yer 3 years overdue for impeller replacement,.... start there....
 
Ok Im looking up parts list on this site, whats the difference between, I, R, MR?

(1988 alpha1 serial OCxxxxxxx)

Which Kit?
47-89984T 5
47 89984Q 5 (looks same as above)
46-96148A 8 (has pump housing aswell, only $2 more?)
 
tuna_man said:
Ok Im looking up parts list on this site, whats the difference between, I, R, MR?

(1988 alpha1 serial OCxxxxxxx)

Which Kit?
47-89984T 5
47 89984Q 5 (looks same as above)
46-96148A 8 (has pump housing aswell, only $2 more?)
Click to expand...

Ayuh,... The MC-1, is old,... The R, 'n MR are Almost Alpha 1s,....

Shop by yer Serial numbers, 'n ya can't go wrong...
You have a late model Alpha 1....
 
Something tells me it's going to be more then one problem here.

1-Just for giggles when were the elbows changed last ?

2-T-stat changed when ?

3-And my favorite the flappers / shutters ? Checked last ?

Good news nothing life changing, bad news gonna cost some money.
 
Master mechanic said:
Something tells me it's going to be more then one problem here.

1-Just for giggles when were the elbows changed last ?

2-T-stat changed when ?

3-And my favorite the flappers / shutters ? Checked last ?

Good news nothing life changing, bad news gonna cost some money.
Click to expand...

Thanks Guy, Bondo & masta. guess mines an original Alpha 1.

Masta
Major Ohaul 2008, every consumable got changed, ($8K in parts).
1/2008
2/ 2008
3/ dont run em........

Hmmmm, this web dont ship to Oz, Ill order from DRM I guess.........
 
First thing is always the impeller. Been said here already. 5 years i'm betting the risers, also. It raw water cooled they are rusted half closed if not more.

Your at the outer limits. Get the complete water pump kit and risers.

You know a complete kit about 500 bucks " some have it lower " 2 elbows... 2 mani's ... all the gaskets in one kit delivered in one box maybe you should consider it. And the rubber bellows how they look?

Just sayin, cheaper now before you get water in your engine then it's maybe 4 grand.
 
Ok, leg is off & pump is out.

Im observing the following, listed in order of photos;


  1. Excessive exhaust heat is burning the paint on the leg. This seems be happening whilst flushing.
  2. Water found on spline of input shaft. Oring stayed behind, in upper box female spline.
  3. Pump water tube starting to melt.
  4. Upper box female spline, water inside. lip seal may be heat damaged, is this critical?
  5. Impellor actually seems fine. is soft & plyable
  6. Hardened melted plastic in top of pump housing
1988 Alpha 1 pump (6)resize.JPG1988 Alpha 1 pump (12)resize.JPG1988 Alpha 1 pump (11)resize.JPG1988 Alpha 1 pump (4)resize.JPG1988 Alpha 1 pump (10)resize.JPG1988 Alpha 1 pump (9)resize.JPG

Ok, this is my theory on whats goin on.
  1. Not enough water is flowing out of elbows, as tstat housing check valves too tight. (old style brass T piece).
  2. lack of flow has caused some melting issues in lower leg.
  3. Pump not performing as well as it should, as it heat damaged.
  4. engine starting to overheat from dodgy pump.

What do you think?

Regards Mark.
 
Ayuh,.... Donno 'bout the impeller, 'but ya need a complete impeller, 'n housing kit,...

It appears No water is movin'... 'n it Ain't because of the T-stat housing...
 
bondo said:
Ayuh,.... Donno 'bout the impeller, 'but ya need a complete impeller, 'n housing kit,...

It appears No water is movin'... 'n it Ain't because of the T-stat housing...
Click to expand...

Ok, ive got a new housing and pump kit, Ill assemble em to the lower box tonight.

My biggest concern right now before I refit lower BOX to leg, is the water i found on the spline. IS THIS A PROBLEM?
 
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No, water gets every where in that area and pulling it apart allows that water to get onto surfaces it may normally not.

What is of concern is there is NO seal leaks............Before gear oil is added it is reccomended to pressure check the drive to ~ 15 psi and it should hold for 2 minutes..........This may be a limitation for you if you do not have the pressure checker......

Did you put the LARGE oring on top of the pump housing? A gental push down is all it needs to seal out the exhaust gasses.

Grease all slipnes, turn the shift shaft splined end fully clockwise and spin the prop c'clockwise till it locks.

as you are installing lower to upper guide the vertical shaft up into seal, also at the same time guide the copper water tube into the plastic guide tube, this can be tricky so be paitent......

once you get the copper tube into the plastic tube and you have the vertical shaft somewhat lineded up gently puch up while keeping the prop locked c'clockwise. Once the vertical splines are lined up the two should come together fairly easy, You may have to spin the propeller C'clockwise to spin the vertical shaft to get the shaft splines to line up with the gear splines in the upper. Again be patient!!!!
as they get close make sure the bronze shift arm is pointing at 12:00 straight forward and guide it onto the shift shaft splines. It ok to put some grease there also if you choose.

If and once you get this far the two halfs should be close to each other. push them together as far as possible. You should be able to get one nut started (hopefully). It make take a little umpff .

Now, you have a preload pin on top of the vertical shaft, Correct? If this is true then the two halfs will NOT come together completely with just your hands pushing.

There will be about a 1/2 inch or so gap. This will be closed by tightening the nuts.

I reccomend installing the two side nuts and the one at 12:00. tighten the left and right somewhat equally and the front one until the two halfs are together.

NOTE::: dont forget the small oring in the oil passage hole if you forget this oil will leak!!!! a small (very small) dab of silicone rtv on it should help keep it in place.

let us know how it goes......
 
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OK reread your posts,

There are two seals in the upper where the splined end of the vertical drive shaft goes, the lower one is there to keep water out and grease in..that is its only job.

If you wanted to replace it go ahead. It does use a special seal driver, (of course every thing for the out drive uses a special tool) also putting it back in with seal lips facing the correct direction is very important........a manual is needed or a good memory of how they came out........

Of course in the real world if you get it out just get the new one back in as long as it goes back in facing the same direction......
 
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kghost said:
No, water gets every where in that area and pulling it apart allows that water to get onto surfaces it may normally not.

What is of concern is there is NO seal leaks............Before gear oil is added it is reccomended to pressure check the drive to ~ 15 psi and it should hold for 2 minutes..........This may be a limitation for you if you do not have the pressure checker......

Did you put the LARGE oring on top of the pump housing? A gental push down is all it needs to seal out the exhaust gasses.

Grease all slipnes, turn the shift shaft splined end fully clockwise and spin the prop c'clockwise till it locks.

as you are installing lower to upper guide the vertical shaft up into seal, also at the same time guide the copper water tube into the plastic guide tube, this can be tricky so be paitent......

once you get the copper tube into the plastic tube and you have the vertical shaft somewhat lineded up gently puch up while keeping the prop locked c'clockwise. Once the vertical splines are lined up the two should come together fairly easy, You may have to spin the propeller C'clockwise to spin the vertical shaft to get the shaft splines to line up with the gear splines in the upper. Again be patient!!!!
as they get close make sure the bronze shift arm is pointing at 12:00 straight forward and guide it onto the shift shaft splines. It ok to put some grease there also if you choose.

If and once you get this far the two halfs should be close to each other. push them together as far as possible. You should be able to get one nut started (hopefully). It make take a little umpff .

Now, you have a preload pin on top of the vertical shaft, Correct? If this is true then the two halfs will NOT come together completely with just your hands pushing.

There will be about a 1/2 inch or so gap. This will be closed by tightening the nuts.

I reccomend installing the two side nuts and the one at 12:00. tighten the left and right somewhat equally and the front one until the two halfs are together.

NOTE::: dont forget the small oring in the oil passage hole if you forget this oil will leak!!!! a small (very small) dab of silicone rtv on it should help keep it in place.

let us know how it goes......
Click to expand...

Hey, Hi Ghost.

Yup, got it, off to the shed to assemble pump.

Your right, dont have the pressure tester. I usually use perfect seal on the sq oil oring?

You lost me with the preload pin thing... I think your refering to the lower box input shaft? No pin ontop, just a small hole, maybe 1/8 or 3/16".

Drained oil from leg today, 1st time in 4 or 5yrs, looked good enough to put back in.;)

9pm here, might not fit lower to upper till morning.

will report back soon.
 
Last edited:
Special Lube 101 or 2-4-C on inpeller etc when assembling pump?

same question for input shaft spline etc?
 
Last edited:
No lube on impeller!!!!!!!!must be water or dry only!!!!!!!!

When putting pump cover on with the impeller in place with its key, you turn the vertical shaft clock wise while putting downward pressure on the pump cover and GENTLY allow the blades to collapse.......

Grease on splines only. I will put a small amount under the big rubber oring that sits on top of the housing but just enough to lubricate it a little..

Perfect seal is used on all orings on lower pump housing only, 2-4-c grease on seal lips, gaskets between lower pump housing and upper go in dry. that is the way I do it.......good and clean and dry...if you use perfect seal on the gaskets it can allow them to become soft and move and tear.........

The small oring between the upper and lower, the factory uses a small amount of rubber adheasive, I use a very small amount of rtv, again very small just to keep it in place and not enough to close off the oil passage hole..........
 
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I could not see the top of the vertical shaft and I was not sure if it was a R, or Alpha drive.

The R and earlier drives had a preload pin at the top of the vertical shaft and both the R and alpha lowers were interchangable so no telling what you have from here.......just bieng cautious......
 
kghost said:
No lube on impeller!!!!!!!!must be water or dry only!!!!!!!!

When putting pump cover on with the impeller in place with its key, you turn the vertical shaft clock wise while putting downward pressure on the pump cover and GENTLY allow the blades to collapse.......

Grease on splines only. I will put a small amount under the big rubber oring that sits on top of the housing but just enough to lubricate it a little..

Perfect seal is used on all orings on lower pump housing only, 2-4-c grease on seal lips, gaskets between lower pump housing and upper go in dry. that is the way I do it.......good and clean and dry...if you use perfect seal on the gaskets it can allow them to become soft and move and tear.........

The small oring between the upper and lower, the factory uses a small amount of rubber adheasive, I use a very small amount of rtv, again very small just to keep it in place and not enough to close off the oil passage hole..........
Click to expand...

Yep, just back from the shed, pump all together, no perfect seal, dry. housing slipped over easy whilst rotating input shaft CW.
sorry did put tiny bit of 2-4-c on impeller blades(tiny), cause the what the service manual said...:(

I used a torque wrench as per service manual, 70 inch pounds, seemed a bit much...

I gonna install lower to upper now, still only 10;30pm. back to the shed.

Ive still got controller in fwd.
 
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The manual did/does NOT say to put grease on impeller!!!

If grease is on the impeller it will NOT seal tight to the stainless steel cup inside the housing..........

Believe me when I say this!!!
 
kghost said:
The manual did/does NOT say to put grease on impeller!!!

If grease is on the impeller it will NOT seal tight to the stainless steel cup inside the housing..........

Believe me when I say this!!!
Click to expand...

Man says "8. Lightly Lubricate water pump body insert with 2-4-C Marine Lubricant with Teflon."

Isnt that the stainless cup inside the housing that impeller spins in?


Back to the shed to pull it apart........
 
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You are correct, I was mistaken............I still say no lube but if you read this before you take it apart then leave it alone.......I am sure it will be fine...........I was instructed by Merc instructors way back in the days of factory training never to use grease.........I guess they changed there minds............lol
 
kghost said:
You are correct, I was mistaken............I still say no lube but if you read this before you take it apart then leave it alone.......I am sure it will be fine...........I was instructed by Merc instructors way back in the days of factory training never to use grease.........I guess they changed there minds............lol
Click to expand...

Phew!!!!!!

Im slumped over PC, (nodding off) waitin for you to get back, and hoping you'd say just that.:)

No i havnt pulled it apart yet, just kept re readin the Man, thinkin Merc cant be wrong???

anyway its only a micro thin film i used, just enought to make it slippery.

However its now late, im not goin back out in the cold, ill fit lower to upper in the morning...


So, how many years you been pushin them pump housings over the impeller, the hard way? ;)
 
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