Alpha one gen 2: diagnosing overheating

[ShoalSurvivor]

er... Alpha 1 gen II

Yesterday, had a hard time warming up. Idled ok, but when revved up, felt like she was going to stall. Eased back down then powered over it and she roared. Sounded like she had to push some sludge out, but she's clean and has been running fine. After that, no firing issues. Unusual and maybe unrelated, but the real problem:


About an hour out, my temp gauge shot up to 220. I was throttled down and took temps:
- starboard side exchanger too hot to touch. > 200 per ir gun.
- core at sender ~ 145-160
- thermostat surface ~ 120
- port side exchanger ~ 105

Gauge appears accurate. No alarms. Running at 2000rpm kept heat @ ~190

When I got home to flush salt water, she heated up really fast > 210 so I shut her down to prevent damage, but I still need to flush her out.

I suspect t-stat but am also suspecting water pump failure. I have a replacement impeller on hand and was going to start there....

Suggestions?

 

[Bondo]

Re: Alpha one gen 2: diagnosing overheating

er... Alpha 1 gen II

Yesterday, had a hard time warming up. Idled ok, but when revved up, felt like she was going to stall. Eased back down then powered over it and she roared. Sounded like she had to push some sludge out, but she's clean and has been running fine. After that, no firing issues. Unusual and maybe unrelated, but the real problem:


About an hour out, my temp gauge shot up to 220. I was throttled down and took temps:
- starboard side exchanger too hot to touch. > 200 per ir gun.
- core at sender ~ 145-160
- thermostat surface ~ 120
- port side exchanger ~ 105

Gauge appears accurate. No alarms. Running at 2000rpm kept heat @ ~190

When I got home to flush salt water, she heated up really fast > 210 so I shut her down to prevent damage, but I still need to flush her out.

I suspect t-stat but am also suspecting water pump failure. I have a replacement impeller on hand and was going to start there....

Suggestions?

Ayuh,.... That's Always the 1st place to start, in Any overheat situation,...

 

[MarkSee]

Re: Alpha one gen 2: diagnosing overheating

I have a replacement impeller on hand and was going to start there....

...and that includes either the newer style 1 piece gasket/faceplate or the 3 separate pieces to install then the new impeller goes in?

Mark

 

[rpdwyer]

Re: Alpha one gen 2: diagnosing overheating

The tube that moves the water from the stern drive to the thermostat housing...loosen the clamp at the T Stat housing and start the engine. Work the hose off carefully as you are near the belts and assuming the impellor is functioning at all, you will have water shooting out. How much water is what you want to see. If you don't have a significant amount from that line, it's the impellor. If you do, then the problem is elsewhere and I would suspect your thermostat.

Don't leave the hose off for more than 5 seconds or so.

I just replaced my impellor yesterday on a 1997 Alpha 1 Gen 2.

--Rick

 

[Haut Medoc]

Re: Alpha one gen 2: diagnosing overheating

After you do the simple test for water actually getting to the engine, (which I suspect it will be fine, since only one side is overheating)...
& since only one side is affected, that is where I would focus on a blockage at the water dumps in the riser/elbow...
You don't say if you have raw or fresh water cooling, but you do run in salt water which will still create scale, even if you flush every time.
For the cost of a gasket, I'd pull the riser on that side & have a peek....

 

[rpdwyer]

Re: Alpha one gen 2: diagnosing overheating

Just a followup thought... if it does turn out that water is not getting to the engine, you should take the extra 1/2 hour and check the exhaust flappers to see they did not get damaged. This was a costly lesson I learned a couple of years ago when I had an overheat and forgot about the flappers.

--Rick

 

[ShoalSurvivor]

Re: Alpha one gen 2: diagnosing overheating

I purchased the full impeller kit last fall, and was going to replace it, but just kept taking her out instead of taking her apart
I know it's due, so I'm going to replace it anyway.

It's a raw water setup (no coolant, just circulates intake).

A blockage in the riser would explain the sudden issue. Usually, the starboard side heats up to 160, but the port side stays cool. my understanding is that the water flow is not symmetrical. Regardless, it occurred suddenly, so I'm going to suspect blockage, or failed pump.

No alarms sounded, and I expect to get the temp issue fixed before I let it heat up past 160 again, but is there anything I should check since it did get to a high heat?

 

[ShoalSurvivor]

Re: Alpha one gen 2: diagnosing overheating

Thanks Rick. I was suspecting I should check something... flappers. New to me, but I'll learn.

 

[ShoalSurvivor]

Re: Alpha one gen 2: diagnosing overheating

After reviewing this animation on water flow:
Cooling System Flow Examples - BoatingHowTo.com

My understanding is this. With T-stat closed, there is no water flowing to the manifolds. That means that exhaust travels through it, but no water to cool. When the engine gets hot enough, t-stat opens and routes hot water through manifold, to riser, and out. That's why that side was always at 160...it's the t-stat doing its job.

If only the right side is heating up, then is seems either:
1) t-stat not directing water to right side (is this possible, since only the starboard side ever got to 160?)
2) insufficient water flow, which impacted the right side due to non-symmetrical design (assuming water routes to one side, then circulation pump, then other side?)

if the flow/circulation is actually symmetrical, then it would be the T-stat. Otherwise, waterpump...
Proceeding with removal.

Any other reasoning, clarification, or lessons are welcomed!

 

[Bondo]

Re: Alpha one gen 2: diagnosing overheating

Ayuh,.... That graphic don't show that some water is Always goin' to the manifolds, regardless whether the t-stat is open or closed,...

 

[rpdwyer]

Re: Alpha one gen 2: diagnosing overheating

There is definitely water getting pushed through and out the exhaust manifolds almost the moment you start the engine... not sure why the diagram would not show that. There are can be a number of reasons why one side was getting hot vs. the other... but I really think it's important for you to start at the ground level and determine you have adequate water flow coming into the T Stat housing from the impellor before anything else.

Regarding the flappers... you should have a rubber exhaust hose that comes off your risers/manifolds and attaches a steel Y shaped exhaust tube that allows the exhaust to leave the boat through the drives. Where the exhaust hose connects to the Y, the flappers are ususally right there. You will likely have to take the riser off as just removing the exhaust hose will not give you enough access... but you can try. Use a large flat bladed screw driver to gently run the tip around the exhaust hose where it slips over the Y tube to break it free after you remove the clamps.

Your flappers should be "closed"... meaning they are gently resting against the side of exhaust tube. They work by letting exhaust and cooling water to push them open to escape but prevent backflow from the outside water coming back up the exhaust from outside the boat and flooding your engine.

--Rick

 

[ShoalSurvivor]

Re: Alpha one gen 2: diagnosing overheating

Please verify my understanding of the flow. It appears that the power steering line runs through the inside of the intake hose (assuming to cool the power steering fluid). That feeds into the t-stat.

For some reason my starboard side manifold is always hotter than the port, but I thought that was normal. Yes? No?

The blue drainout plugs... when am I supposed to use these? should I drain after flushing?

are the risers what I'm pointing to with the big red arrows in this picture (and referring to as the exhaust manifold)?


the area shaded in green was kind of crunchy when I first squeezed it. All other hoses were quiet. It's quiet now, but I inspected (squeezed) the whole hose, so did I just loosen up a bunch of scale?

 

[Bondo]

Re: Alpha one gen 2: diagnosing overheating

Please verify my understanding of the flow. It appears that the power steering line runs through the inside of the intake hose (assuming to cool the power steering fluid). That feeds into the t-stat.

For some reason my starboard side manifold is always hotter than the port, but I thought that was normal. Yes? No?

The blue drainout plugs... when am I supposed to use these? should I drain after flushing?

are the risers what I'm pointing to with the big red arrows in this picture (and referring to as the exhaust manifold)?
View attachment 226409

the area shaded in green was kind of crunchy when I first squeezed it. All other hoses were quiet. It's quiet now, but I inspected (squeezed) the whole hose, so did I just loosen up a bunch of scale?

View attachment 226410

Ayuh,.... Water comes from the drive, through the P/S cooler, to the T-stat housin',...

Generally speakin',.. ya, starboard side is usually somewhat warmer,...

The drain plugs are for drainin' the water outa it, before it Freezes, crackin' the block,...

You don't have risers, you've got batwing 1 piece manifolds,... Get Rid of 'em,... they're Junk, from day 1,...
Ya need to find a Kit, to convert to manifolds, 'n risers,...

The crunchy soundin' hose, sometimes has a spiral wire liner in it,...

 

[ShoalSurvivor]

Re: Alpha one gen 2: diagnosing overheating

I have a gear oil monitor. Will that fluid all drain through the vent/fill holes in the lower unit when I drain? I saw that someone pinched the tube off with vice grips inside the boat to minimize draining and filling... is that the recommended procedure? or should I allow it to all drain?

 

[MarkSee]

Re: Alpha one gen 2: diagnosing overheating

I have a gear oil monitor. Will that fluid all drain through the vent/fill holes in the lower unit when I drain? I saw that someone pinched the tube off with vice grips inside the boat to minimize draining and filling... is that the recommended procedure? or should I allow it to all drain?

No, pinching off the hose is not recommended; you want it all to drain then refill from the bottom up.
Be sure to remove the cap from the bottle when draining/filling.
Here is a link to Dons sticky: adults only, Merc section and scroll down to the service manual section and there is a link to an online site where you can read the official procedure.
You want serv manual #14 for an alpha1, gen 2.
http://forums.iboats.com/mercruiser...cellaneous-mercruiser-information-329915.html

Mark

 

[midcarolina]

Re: Alpha one gen 2: diagnosing overheating

A little while back I was doing some looking around at old posts...... and I read a thread where one or two of the experts talked about modifying and using a pump up garden sprayer to pump the gear oil in.....

I happened to have a 1/2 gallon sprayer doing nothing at all.... So I modified it and tried it, works a treat! worth the five minutes it takes to modify pump.

 

[ShoalSurvivor]

Re: Alpha 1 gen II: diagnosing overheating

Re: Alpha 1 gen II: diagnosing overheating

Impeller had an arm pulled back, and was unevenly worn. This will be replaced. Inside surface is free from scratches/mars, but needs a little emery work.


There was no water or metal in the drained gear lube. Looks just like what goes in the top monitor/resevoir, but seems thicker. And stinks. I'm assuming that fluid travels down to the drive from the reservoir, but not back. I saved the contents of the reservoir since is smelled fresh. My plan is to use what I saved in a flush, then replace it all.

Here's a photo from under the plate. A little bit of scale, but not to bad for a salt-water rig.


Any comments/feedback is welcome. Thanks.

 

[ShoalSurvivor]

Re: Alpha one gen 2: diagnosing overheating

Back to the overheating problem, the impeller is suspect, but I don't think that was enough to result in the overheating, and it doesn't explain why only one side would overheat. I think I should investigate further for blockages. If water is getting to the t-stat, then there should be pretty equal flow to both batwings... do I need to remove those to inspect for a blockage inside? Is there anything to see in there if I take it apart, or am I just 1/2 way to the conversion ?

I'm not ready $$$ to do a batwing/riser conversion, unless its really the problem. $500-1k is a lot to shell out for new manifold/risers. But, I'm listening.... do they really need to be replaced? Is their job just cooling, and if I don't have a cooling issue they are fine? Will they lead to premature engine failure, besides from overheating?

I'm going to replace the t-stat, just to be safe. Should I use a 140 or 160?
Please help with correct replacement parts. (does the tstat come with housing gaskets, or is there a kit?)

Engine is a 2004 Repower 4.3 Alpha I Gen II with 4bbl carb.
drive SN: 0L102679 1.63R is stamped in, but 1.81R is hand written next to it.
Engine S/N: 90004747

Thanks!!!

 

[Bondo]

Re: Alpha one gen 2: diagnosing overheating

Back to the overheating problem, the impeller is suspect, but I don't think that was enough to result in the overheating, and it doesn't explain why only one side would overheat. I think I should investigate further for blockages. If water is getting to the t-stat, then there should be pretty equal flow to both batwings... do I need to remove those to inspect for a blockage inside? Is there anything to see in there if I take it apart, or am I just 1/2 way to the conversion ?

I'm not ready $$$ to do a batwing/riser conversion, unless its really the problem. $500-1k is a lot to shell out for new manifold/risers. But, I'm listening.... do they really need to be replaced? Is their job just cooling, and if I don't have a cooling issue they are fine? Will they lead to premature engine failure, besides from overheating?

I'm going to replace the t-stat, just to be safe. Should I use a 140 or 160?
Please help with correct replacement parts. (does the tstat come with housing gaskets, or is there a kit?)

Engine is a 2004 Repower 4.3 Alpha I Gen II with 4bbl carb.
drive SN: 0L102679 1.63R is stamped in, but 1.81R is hand written next to it.
Engine S/N: 90004747

Thanks!!!

Ayuh,.... The impeller pump is more than Suspect,... it's Beat,....

Do the Whole kit, housin', 'n all, you need it,....

The manifolds just cool themselves, not the motor,... It's how the motor get's rid of it's water,...
Usually, the risers get plugged up with rust, 'n junk, causin' a restriction,... low to no flows,...
With 2 pc. manifolds, you can pull the risers, 'n check, replacin' what's necessary,...

With yer's, ya can't,...
You can only peek in through any water ports,...

The Problem with yer's is, the castin's are irregular, 'n inferior,....
Due to variations in wall thicknesses, yer's could dump their entire load of water, into the exhaust ports, swampin' yer motor, causin' Hydro-lock,...
At that point, yer motor is an Anchor, 'n little more,...

You've been on borrowed time, for Along time,....

If yer Handy, swappin' on a set of used freshwater exhaust is always an option,...

 

[ShoalSurvivor]

Re: Alpha one gen 2: diagnosing overheating

I will replace the housing, impeller, seals and gaskets etc.

I am still going to replace the t-stat but need to know what temp to us: 140, 160? (2004 4.3L 4bbl Gen+)

I'm going to do all that, and then see if the temp problem is solved. If not, I will proceed with manifolds.

Thanks!