mercruiser 5.0 mpi overheats at idle

[Fishermark]

Re: mercruiser 5.0 mpi overheats at idle

A half inch allen wrench will work - or you can buy the special Mercruiser tool.

 

[nauticool]

Re: mercruiser 5.0 mpi overheats at idle

outdrive and bell housing is off.

found UJ bellows ok, exhaust bellows were split due to installation error (screw located at base and fouling on bell housing), control cable bellows ok.
Water pump does not look as if it was changed last year and impeller has some scratch marks on each paddle.
Also the base of the pump looks as if part of it is either a bad mould or has melted! see pics.
The plate is not warped but has score marks in the middle and some pitting.
Will be fitting a complete new pump kit, not repair kit as its not expensive. Also new pick up pipe and exhaust bellows.
On the pics you can see a spring type ring around the shaft on top of the pump before it was removed. not sure where this came from. any ideas?
all waterways look clear and im not confident ive found the problem.

sorry but my camera doesnt like close up pictures

http://www.youtube.com/watch?v=hyS25175tQ0

I think the plan is to change all servicable items with mercruiser parts and test again, then onto engine if this does not solve the problem. should i be ordering a new thermostat as part of a service item? how long do they last on these raw water cooled engines?

As always comments and suggestions gratefully received

 

[nauticool]

Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Will mercruiser 5.0mpi work with Alpha 1 gen 1?

If you look at my previous threads you will notice I'm having a couple of issues at the moment. The more serious one is engine overheat at idle. If you rev the engine it will cool to normal operating temp, idle and same happens again.
I have just spoken to a dealer and he says the water pump in the alpha 1 gen 1 is too small for that engine!!!
Could this be true? The engine has been working fine but in the summer I don't spend a lot of time at idle. In the winter I run the engine for 30mins every week at the pontoon. Could this be why I notice it more now? This is the first winter Ive had the boat.
The water pump is in a bad way so was going to change it to see if this cures the problem.
Maybe it does work and is just borderline?now the pump is bad has it pushed the borderline? Maybe running at idle everyweek for 30mins is not such a good idea?
For reference there is no water pump on the engine and it is raw water cooled only.

 

[Don S]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Why don't you just fix the pump and see how it works. It should cool your engine fine at idle.

 

[nauticool]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

That's still the plan Don, just wanted to see if anyone had any opinions or experience with this setup.
Basically the dealer has put the frightners up me! He seemed certain. However he couldn't tell me why it worked with the original 5.7 installed.

 

[Don S]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

The MPI engines don't run any hotter than a carbed engine. Back in the late 80's, the 454 was used with the same pump you have for your 5.0.
Your dealer wants YOUR money.

 

[180shabah]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

...and now is a good time to check the water hoses between the pump and engine. Look for soft spots where they may have collapsed internally, and obviously any kinks are bad.

 

[Don S]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Look at his overheat post, he also has a collapsed hose.

 

[Bondo]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

The more serious one is engine overheat at idle. If you rev the engine it will cool to normal operating temp, idle and same happens again.
I have just spoken to a dealer and he says the water pump in the alpha 1 gen 1 is too small for that engine!!!
just wanted to see if anyone had any opinions or experience with this setup.

Ayuh,... I fought that very Problem for quite a few years.... About 2 years ago, in casual conversaion here with Don, it dawned on me the Actual Problem....

The Alpha 1, does in fact move slightly less water per rpm, than the Gen.IIs...
The Fix is Cheap,+ super Simple...
Once you've swapped out the impeller,+ verified that the system is clear,...
Buy the Check-ball kit for the T-Stat housing,.. Install it,+ your overheat at idle issue is Fixed...
The checkballs hold back the expelled water enough to keep the motor heat under control....

Been there, Done that.....

 

[achris]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Water pocket cover?

 

[Don S]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

I think bondo is right, but wasn't sure he would be able to use the old style t-stat housing on the MPI manifold. I looked at the different setups and what engine he has in the video from his overheat post. He needs the MPD (Multi Point Drain) system on his engine, but has the single point drain, which really confuses the cooling system.
Download manual 37 and look at pages 10A-2 and 10A-3 you will see what I mean. He has what is on 10A-2. I'm afraid that drain system is also something he is going to learn to hate in the long run. With all the different hose setups and thermostat setups, it's probably going to be about the same price to put on the bigger pump. Having worked on those pumps before, they are the worst (Sorriest) design Mercruiser could have come up with. So I really don't know what to suggest.

Here is a picture of his engine I took from the video.

 

[Bondo]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

I think bondo is right, but wasn't sure he would be able to use the old style t-stat housing on the MPI manifold. I looked at the different setups and what engine he has in the video from his overheat post. He needs the MPD (Multi Point Drain) system on his engine, but has the single point drain, which really confuses the cooling system.
Download manual 37 and look at pages 10A-2 and 10A-3 you will see what I mean. He has what is on 10A-2. I'm afraid that drain system is also something he is going to learn to hate in the long run. With all the different hose setups and thermostat setups, it's probably going to be about the same price to put on the bigger pump. Having worked on those pumps before, they are the worst (Sorriest) design Mercruiser could have come up with. So I really don't know what to suggest.

Here is a picture of his engine I took from the video.

Ayuh,....

Ya know how I'm into Creative Engineerin' 'n all,.....

Why can't nauticool get the Check-ball "Kit",+ put it into That T-Stat housing,..??
It appears in the picture, that it would fit perfectly into the housing at the ports, just Under the blue plug...
Aren't those in fact the hoses goin' to the risers,..??

pretty much looks like a Cure to me.....

 

[Don S]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

I have some other points I will can post pictures of and other parts. But the big thing with his tstat housing is the outlet for the T and the checkballs is 3/4 or 1" pipe, where he has only a 3/8" plug now. That would sure cut down on the water flow. The other BIG thing is the passages inside the housing. It's not just wide open, there are drilled passages designed to control the flow of water. Have seen this in both Merc and Volvo housings, the newer the are the more complex they become, and no real pictures to prove my point either.

 

[JustJason]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Ugh... any chance Don you can merge this guys' 2 threads? Confusing going back and forth.

Nauticool. Was the reciept you found an actual reciept and not maybe just an estimate????
There are 2 types of water pumps. Hi-pressure low flow pumps, or hi-flow low pressure. The gen 1 drives use a pressure pump, whereas the gen 2 is more of a flow pump.
Either way... either pump will work fine.
Throw a 5 gallon rubbermade bucket in the boat. Disconnected the water input hose that comes up from the transom plate to the tstat housing. With the boat in the water, (and not on the muffs) start the engine and run it at idle for 30 seconds with the hose aimed at the rubbermaid. (start with a cold engine). How many gallons did you get?

 

[Don S]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Ugh... any chance Don you can merge this guys' 2 threads? Confusing going back and forth.

I was going to do that earlier, only got sidetracked and forgot about it.

Either way... either pump will work fine.

That was what I was thinking also, till bondo posted the comment about the check balls. Then you have to look at how the single point and 3 point drain systems flow water and you realize the manifolds are getting all the cooling water and the engine is missing out.

Throw a 5 gallon rubbermade bucket in the boat.

He can't do that. All he has is an old 5 gallon bucket and doesn't want to go looking for the rubbermade brand.
Danged Jason, you selling rubbermade products too

 

[JustJason]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Danged Jason, you selling rubbermade products too

har har Don

I guess I would need to see pics of the rest of the cooling system. If he has a 3 point drain then the plumbing could be correct. If he has a 7 point drain then the blue plug in the tstat housing shouldn't be there.

The alpha pump will work with either setup, Nauticool you need to look at the service manual and compare what you actually have against the book.

Has this ever worked, or has it overheated at idle since the first day you owned it.

 

[Don S]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Jason, look at the picture in reply #32. That is his engine I took from his youtube video. Look at the pictures in manual #37 that I mentioned also in reply #32.
Like I said in #24, fix the pump in the drive, and give it a try.
I would sure hope he would do that instead of all this other stuff bondo and I were talking about.

 

[JustJason]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

I hear where your comming from Don. These plumbing systems get more and more complicated (note I didn't say better) every generation.

Which is why I'd like to know the answer to this question before I can really say anything further.
Same As I asked before...
1. Has this engine ever cooled itself correctly since you owned the boat, or has it been overheating at idle since day 1?

Don, unless i'm missing something here (which I probably am ) have a look at the same picture and compare it to SM37 pg 10A-2

The hose I circled shouldn't be there.

Which is why I'd be interested to see more pic's of the entire cooling system, the more the better. Where is that hose comming from and exactly where is it going? I wonder if it's never worked since day 1 if there is a mish-mash of a cooling system hacked by a previous owner.

 

[Don S]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

The system is normal. The nice thing about that hose to the right of the fitting you have circled, is it has a part number on it and the number is for hose #22 in the parts book. It does not go to the thermostat housing, it goes from one riser to the next and into a Tee (#20) and down to the drain valve (hose 19). I put the numbers on the picture that corresponds to the part numbers in the parts breakdown.

 

[JustJason]

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

Re: Will mercruiser 5.0mpi work with Alpha 1 gen 1?

You are correct again Don. When I first looked at the picture and compared it to the manual it was looking like in the picture it was connecting to the tstat housing.

I think this is getting more complicated than it should.

At this point if the plumbing is verified good, i'd drop the lower and have a look at the waterpump... inspect and replace if necessary.
Have a look at the tstat. Throw it in some boiling water and make sure its fully opening.

Regardless of what reciepts may say about the last water pump change... 10-15 seconds of dry operation is enough to cause the pump not to operate correctly.