Carb Adjusting and Overheating Issue

J

JFrog

Seaman
Joined
Sep 23, 2012
Messages
61
Hey guys,

Finally got my AQ125B running, however, I'm running into some carb and overheating issues.

First, everytime I try to rev the engine up above 3500rpm or so it begins to putter out and die. What might the cause/s of this be?

Second, what is the "normal" operating temperature of this engine? After about 3 minutes of running the temp was already around 220F!I know there is probably alot of different reasons why the engine is overheating, but where should I start? The boat has been sitting since 1998.

Thanks,
Keith
 
Don S

Don S

Honorary Moderator Emeritus
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Messages
62,321
Re: Carb Adjusting and Overheating Issue

First, everytime I try to rev the engine up above 3500rpm or so it begins to putter out and die. What might the cause/s of this be?
Click to expand...

Carb plugged up (after sitting 14 years, I couldn't imagine it not being plugged up), when was the last time it had a full tuneup, including setting the dwell, then the timing, compression check, etc.
What shape is the timing belt in.


Second, what is the "normal" operating temperature of this engine?
Click to expand...

190 is normal, 220 is way too hot. First thing to check in any overheat on a marine engine is the impeller. again, after 14 years, it couldn't possibly be any good.
Before you ever think about going to the water, at least, replace the ujoint bellows on the drive, and change the gear lube.
 
C

captmello

Captain
Joined
Jun 30, 2008
Messages
3,855
Re: Carb Adjusting and Overheating Issue

You've got a lot to check over if it's been sitting for 15 years! I'd stop running it.

the raw water impeller is the first thing to check. It will need replacing regardless of how it looks.
I would also pull the upper gear box off the outdrive to replace the bellows and check the ujoints and flywheel bearings, here's how.

http://forums.iboats.com/showthread.php?t=309095

While the upper is off, I would replace the intake fitting gasket and/or the intake fitting which is just below the ujoint bellows. they tend to go bad and can lead to overheating as well

Normal op temp is about 190 deg.

Are you reving the motor in neutral on muffs? If so this in not a good test, however if it won't rev, even in nuetral I would guess you are needing a complete ignition tune up.


Since I don't know your level of ability, I will not go into specifics on any of these items unless you ask.:)
 
J

JFrog

Seaman
Joined
Sep 23, 2012
Messages
61
Re: Carb Adjusting and Overheating Issue

Well, before all of this, I took the carb apart, cleaned out all the jets, bowl, etc. and replaced all of the gaskets, so I'm pretty sure its not plugged up anymore.
If its not plugged, could the problem be caused by the other things you mentioned?
If so, I'm not sure about the last time it was tuned, not sure what the dwell is (noob), I'll need to check the timing and compression still.

Got it, replace the impeller if needed, replace the ujoint bellows and change the gear lube. In regards to the gear, which gear are you speaking of? Again, noob to boats. Really enjoying learning though!
 
J

JFrog

Seaman
Joined
Sep 23, 2012
Messages
61
Re: Carb Adjusting and Overheating Issue

Hey cap,

Got it, I won't turn it over anymore until I get these things finished. Yeah, my father-in-law just let it sit after the steering cable seized up (normal wear and tear), he's just lazy.
Anyway, I'd like my son (2 year old) to experience what I experienced out on boats as a kid, so I'd really like to get this boat running again, so I decided took take on the project since I've rebuilt a 62 Ford Galaxie.

Even so, I'm still new to carb tune-ups.

Yes, was reving on muffs in neutral, will stop now though.

Oh, any specifics you guys can give me would be great! I love this kind of stuff and really want to learn more! Other than the engine itself, this is all new to me. For example, don't even know where the impellar is, but can't wait to find it :rolleyes:

Thanks,
Keith
 
C

captmello

Captain
Joined
Jun 30, 2008
Messages
3,855
Re: Carb Adjusting and Overheating Issue

the impeller is in the round housing on the front of the motor lower half to the port side with two pipes coming off it.

Compression check for sure.
 
Don S

Don S

Honorary Moderator Emeritus
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Aug 31, 2004
Messages
62,321
Re: Carb Adjusting and Overheating Issue

If you pump the throttle (engine not running) do you get a strong squirt of gas from the J tube on top of the carb?

Yes, the other things I mentioned could cause the problem, that's why I mentioned them.
 
J

JFrog

Seaman
Joined
Sep 23, 2012
Messages
61
Re: Carb Adjusting and Overheating Issue

Hey Don,

Yep, I get a nice strong steady stream of fuel that jets out of the J tube every time I pump the throttle.

Okay, tore into the entire cooling system this afternoon and WOW, what a mess! Most of the impellar vanes were crushed, tore or missing, some of which I found at the top of the heat exchanger. Pretty much every gasket in the entire system is dry and cracked. I bled the coolant and found this dark greyish goop at the bottom of the coolant tank. Took off the coolant pump, which looked good, but I'll change out those gaskets too.

So far, here is a list of parts I'm thinking I'm going to need. Let me know if this sounds about right:
New raw water pipe gaskets
New impeller and gaskets
New raw water strainer housing (cap busted off)
New coolant pump gaskets
New heat exhanger gaskets
New coolant tank cap (rusted and not holding pressure)
New thermostat
New bellows
New intake fitting gasket and/or the intake fitting (depending on how it looks, haven't tore into the sterndrive yet)
Gear lube

Thanks again,
Keith
 
C

captmello

Captain
Joined
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Messages
3,855
Re: Carb Adjusting and Overheating Issue

Looks like a good start!

Take your time, do it right. Hows the rest of the boat look?
 
J

JFrog

Seaman
Joined
Sep 23, 2012
Messages
61
Re: Carb Adjusting and Overheating Issue

The rest of the boat is in pretty good shape. Fortunately, the boat always had a cover on it so really the only issues I'm dealing with are issues tied to sitting for 15 years.
 
A

Alan Lloys

Petty Officer 3rd Class
Joined
Aug 16, 2012
Messages
99
Re: Carb Adjusting and Overheating Issue

I have the same exact engine that I just worked on on a 1985 boat.
This one had been used this year before I bought it with a broken circulation pump.

I had issues with it as it had not been properly maintained for a few years.
Here is the list of things I performed to get it going:

1) Cleaned the carb and replaced gaskets. Mine sucking in air between the carb and the manifold so it would stumble at 2000-2500 RPM when it was going from idle jet to high speed jet
2) Checked compression on all 4 cylinders - I had about 130 psi cold (min is 128 psi warm per manual)
3) Replaced the circulation pump with a customized pump as the old one is no longer available. Note if you have to do this that I will likely offer the modified pump for sale. The OEM solution which includes a new pump and heat exhanger housing is $ 1,200. My modified pump will probably be around $ 250 and is a direct bolt in fit. As part of this I also flushed and replaced the coolant.
4) Replaced the water impeller and the water line gaskets.
5) Adjusted the points and set the proper advance. I was never fully happy with how it ran so I replaced the points with a Pertronix electronic ignition kit. It is a fairly simple change and it made a huge difference. Only note is that I had to modify the distributor bracket in order to get the correct advance set.
6) New spark plugs - I put Bosch 7900 in there.
7) Of cause changed oil and filter. I put full synthetic in.

After these changes the engine runs absolutely perfect. It does only have 265 hours on it though so it may not be a fair comparison.

On mine I found that the water inlet hose from the outdrive was kinked and restricted the flow of cooling water. I found a piece of radiator hose with the correct bend in it and have been using that since. The OEM hose is also no longer available. After I fixed that it is very steady at 180-190 F coolant temp.
Note that the 270 out drive has a hole in bottom and hence it is not easy to run on muffs. When I first tried I had it over heating at anything above idle. I now just use a very big Rubbermaid tote, fill it with water and let the water run into it and then lower the out drive down so the water intakes are covered.

Hope some of these things helps you. I have done some work to this engine as I bought the boat basically for scrap value as it was deemed to expensive to replace the circulation pump at $ 1,200 + labor.
I will be happy to help out if you have specific questions.
 
J

JFrog

Seaman
Joined
Sep 23, 2012
Messages
61
Re: Carb Adjusting and Overheating Issue

Hey Alan,

Great information, thank you!

Much of the things you did I have done as well. Cleaned the carb and replaced the gaskets. New plug wires, coil, plugs, cap, rotor and contact set. Changed the oil, oil filter and fuel filter. New fuel pump.

I need some help doing the compression check for I have never done it before and also need help as far as timing goes. If you wouldn't mind, could you run through the steps for me on these two things? Of course, I won't do these things until I've replaced the parts listed above so I can keep the motor cool.

Thanks,
Keith
 
J

JFrog

Seaman
Joined
Sep 23, 2012
Messages
61
Re: Carb Adjusting and Overheating Issue

Hey guys,

Do any of you happen to have the part number/s for the intake fitting gasket and/or the intake fitting?
Also, the part number/s for the Drain Plug O-Ring, Fill Plug Gasket and the two other O-Rings mentioned in http://forums.iboats.com/showthread.php?t=309095 mentioned by Don?

Thanks,
Keith
 
J

JFrog

Seaman
Joined
Sep 23, 2012
Messages
61
Re: Carb Adjusting and Overheating Issue

Hey Cap,

Ah, didn't know those part numbers were for my drive as well. My bad. Cool.

Ugh, can't get the upper off because I can't get the helmet pin removed to lift it out of the way. How do I get the pin out and then how do I remove the upper? I already have everything removed except for the helmet pin.

Thanks,
Keith
 
C

captmello

Captain
Joined
Jun 30, 2008
Messages
3,855
Re: Carb Adjusting and Overheating Issue

If you have a 4 hole pin like this

Helmetpin002.jpg


You can use a 1/4 bolt in the two smaller threaded holes. this will jack the pin up and out. the long lower bolt that holds the shift cover will work, I believe. but depending on how tight the pin is, you may need two bolts.
 
J

JFrog

Seaman
Joined
Sep 23, 2012
Messages
61
Re: Carb Adjusting and Overheating Issue

Hey guys,

Got the upper detached from the lower after getting the pin out of the helmet but I ran into some more snags.

Where is the gear oil drain? I now have gear oil everywhere because I didn't realize that the lower was basically a oil pan..lol!

Also, how do I disconnect the U-Joint from the upper? I can't get the upper removed because it's still attached.

Thanks,
Keith
 
C

captmello

Captain
Joined
Jun 30, 2008
Messages
3,855
Re: Carb Adjusting and Overheating Issue

The drain is at the bottom of the outdrive, Use straight 30W when refilling.

The ujoint should come off with the upper gear box. Sometimes the ujoint yoke gets corroded onto the driveshaft. Hopefully yours isn't too stuck...Was this boat used in salt water much?
 
J

JFrog

Seaman
Joined
Sep 23, 2012
Messages
61
Re: Carb Adjusting and Overheating Issue

Is the drain plug a big flat head screw? If so, I found it.

Yeah, ended up answering my own question with the upper sliding right off. I ended up getting the upper and lower bellow off along with the intake fitting, gasket and hose. It's all going on my huge parts list..lol!

Thanks guys! I'll keep this post updated as parts come in.
Keith
 
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