Carb Adjusting and Overheating Issue

[Alan Lloys]

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

Glad to hear your progress on the out drive. I have not had mine apart yet as the bellows are in great shape. I will likely wait until end of next season before I take it apart and also check the PDS bearing.
My manual says to use the same oil as for the engine for the out drive. I put 10W-40 synthetic in it. Either way I don't think you can go wrong.
BTW see if you can download both the owners manual and the service manual for your engine.
If you do a search for AQ125B and put in "owners manual" or "service manual" you should be able to find a free download. I printed them all out and have them saved. If you cannot find them PM me and I will see if I can email them to you.

Compression test is the simplest of the two tests. You have to purchase a compression tested at an auto store. I bought a cheap one from Harbor Freight for around $ 15. You run the engine warm and shut it off. I remove the main wire on the distributor so it will not run. Then remove a spark plug one at a time and screw in the compression tested. Then crank the engine a few seconds with the starter and you should have a reading.
The spec calls for warm engine, but since I always end up burning myself on the engine or spark plugs I usually do it fairly cold. If you compression is above minimum you are usually good. The compression will only go up if it changes at all when the engine is warm.

The timing and dwell angle is a bit more difficult to set. First you set the gap on the point. You then need a dwell angle meter to measure the angle. This is basically fine tuning the gap on the point. It is a bit of a hassle to work with as you have to take the distributor cap on and off a lot of times to make adjustments. BTW my cheap HF meter has a dwell angle measurement, but it was not showing any correct numbers at all - so I don't think that portion works (cheap China). With the Pertronix unit you never have to worry about the point gap as it is replaced with the an electronic component and a magnet sleeve.

Timing will have to be set using the same method for either ignition system.
This will require a timing light - it is basically a strobe light that fires in sync with the spark plugs.
You will hook this up to a battery and then to cylinder 1 spark plug wire.
At the base of the distributor there is one bolt holding the distributor shaft to the engine. You loosen this one a little but do not take it off.
Start the engine and set it to idle. You can now turn the distributor slightly clock or counter clockwise.
Use the timing light to see where the timing mark on the crankshaft is on the scale. You should be somewhere between 5 and 10 degrees.
Then rev up to 4200 RPM and check again. You should now have 32-36 degrees of advance. Fine tune the distributor to get this and then tighten the bolt.
Run at idle and recheck again.

You may notice that the bolt holding the distributor to the engine sits in a slotted hole. This limits how much you can turn the distributor either way. In my situation I could not get it moved far enough counter clockwise to get the timing to the correct advance. I think it was too much if I remember right.
I had to take it off completely and just filed the slot another 1/4" longer or so.

Hope this info helps you

 

[JFrog]

Re: Carb Adjusting and Overheating Issue

Hey Alan,

This is fantastic information, thank you!

Oh, really quick. What should the idle rev be set at and what is the max rpm this engine goes to before redline?

Thanks,
Keith

 

[PiratePast40]

Re: Carb Adjusting and Overheating Issue

Oil threads show up all the time and it's usually about whatever you feel like doing. However, in this case, Volvo Penta does NOT recommend synthetic oil in the AQ series outdrive. I believe it has something to do with the cone clutch. But as usual, it's your boat, you can do whatever you want to do.

 

[Alan Lloys]

Re: Carb Adjusting and Overheating Issue

Oil threads show up all the time and it's usually about whatever you feel like doing. However, in this case, Volvo Penta does NOT recommend synthetic oil in the AQ series outdrive. I believe it has something to do with the cone clutch. But as usual, it's your boat, you can do whatever you want to do.

I agree, I see all kinds of heated discussions on that. I feel pretty happy with it for my small engines, but it is more because it only adds $20 a year on my oil budget and I figured it would not hurt.
I was actually not aware that Volvo is not recommending synthetic oil for the out drive. Maybe the synthetic is too "slippery" and would make the cone clutch slip? I have only used it for a few hours after I changed the oil so there it still time to change.
Can you refer to any sites that talk about the issue with synthetic? I always like to learn new things.

Hey Alan,

This is fantastic information, thank you!

Oh, really quick. What should the idle rev be set at and what is the max rpm this engine goes to before redline?

Thanks,
Keith

According to the manual the idle should be set at ~900 RPM when warm and not in gear. I find that it is a bit too low for me as it the engine almost dies when I put it in forward at idle. I set mine to about 800-900 when idle in gear which is about 1000-1100 neutral speed.

On boat engines there really is not the same max RPM as there is on a car due to the lack of gears. Note that there is nothing limiting the RPM when you are in neutral or when you have it out of the water. So be careful about over revving the engine as it can cause damage. If you gave it full throttle you could pull 6000+ RPM and damage it.

In a boat you typically talk about WOT speed. This is the RPM at wide open throttle when the boat is in the water and cruising. You use this to size your propeller and pitch correctly. Per the manual the maximum WOT is 4800 RPM. So I would also not take it much above that in neutral. The continuous cruising speed should be 300-500 RPM below the WOT number.
Note that with your load and propeller you may only get 4500 RPM at WOT for example. Then you max cruising speed is 4000-4200 RPM.
In general you want to propeller to make your WOT as close to the max RPM as possible for maximum hp.

 

[PiratePast40]

Re: Carb Adjusting and Overheating Issue

Here's a thread: http://forums.iboats.com/showthread.php?t=524135&page=2&p=3552599&highlight=synthetic%20oil%20aq%20outdrive#post3552599

 

[captmello]

Re: Carb Adjusting and Overheating Issue

One other note, With the upper gear box removed, grab the drive shaft and see if there is any play in the shaft. If so, You'll need to replace the bearing.

Also Regarding the compression test,

Then remove a spark plug one at a time and screw in the compression tested. Then crank the engine a few seconds with the starter and you should have a reading.

Remove all the spark plugs first, not one at a time.

Alan - That water pump is a great idea. I'll bet you could sell quite a few of those!

 

[Alan Lloys]

Re: Carb Adjusting and Overheating Issue

Also Regarding the compression test,

Remove all the spark plugs first, not one at a time.

Alan - That water pump is a great idea. I'll bet you could sell quite a few of those!

You are correct that the proper procedure is to remove all the spark plugs. It makes it easier for the starter motor to spin the engine as it will not have to compress on the other cylinders. Usually I am too afraid of getting the spark plug wires mixed up so I am just doing one at a time. It is harder on the battery and starter motor though.

Currently I am just feeling out if there is a market for the pumps. I should have a revised version complete in a few weeks and I can post some pictures in the technical section.

 

[JFrog]

Re: Carb Adjusting and Overheating Issue

Hey guys,
I have another quick question for you regarding carb tuning. Does anyone know how many turns the adjusting screw needs to come out from bottom?
Thanks,
Keith

 

[Alan Lloys]

Re: Carb Adjusting and Overheating Issue

I know it is in the owners manual, but I don't have it near me right now.
From memory though I believe it is 1.5 turns out from the bottom.
There are two different carbs though for this engine and I believe the other one is 2 turns.
Anyway this should get you in the ball park.

 

[JFrog]

Re: Carb Adjusting and Overheating Issue

Hey guys,
Quick update on this thread. Have replaced all the parts I listed earlier and everything went on fairly simple. Well, everything except the coolant pump. Wow that is a bear to get on correctly. Trying to get the sealing ring to sit properly while also getting each bolt lined up is a pure nightmare. Anyway, it's in there now.
Ran into one snag though. For some reason one of the bolt holes that holds the strainer housing to the heat exhanger lid stripped. I think I'll go ahead and re-tap the hole to the next bolt size up and get that bolt to replace it. Hopefully this will solve that problem. I was going to leave it as is but kept having water leak out between the strainer housing and heat exchanger lid.
Next thing i need to do is check the compression and timing. The carb seems to be working fine but I still can't get the engine to rev above 2000 rpm. I just need to go get a timing light and compression test kit. I'm pretty sure I can get the engine timed right with the timing light however: if the compression is bad in one or more cyclinders, what might this be caused by and what is the fix for the problem/s?
Thanks,
Keith

 

[captmello]

Re: Carb Adjusting and Overheating Issue

Do you have points? If so they should be replaced and/or checked with a dwell meter and adjusted. Then time the motor. Many just gap the points with a feeler, but that is just a starting point.

Try youtube for help timing/setting the dwell.

Low compression can be caused by many things. Do the test and see what you find.

 

[JFrog]

Re: Carb Adjusting and Overheating Issue

Yeah, I went ahead and replaced the points already but haven't adjusted them yet as I don't have a dwell meter or feeler gauge. I've been checking out youtube for videos and have seen guys just using the feeler and stating that that is all you need to do. I guess I need to do both though.
Seems like there are quite a few new tools I need to invest in. So far it looks like I need to get a compression tester kit, timing light, feeler gauge and dwell meter. Is there anything else I might need to get to get this engine timed/tuned? I'm afraid to find out what I'll need if the compression is too low...lol.
Thanks,
Keith

 

[Alan Lloys]

Re: Carb Adjusting and Overheating Issue

I would start with the compression test. If you have no compression on multiple cylinders the engine may be terminal.
It is quite a big project to fix if you have a major cylinder issue.
If however you just have reduced compression it could be as (relatively) simple as new rings.

I got most of my tools from Harbor Freight as I only use them once a year or so. Don't get their dwell meter though - it doesn't measure anywhere near accurate.

A feeler gauge will get you close enough that you should easily be able to get the engine above 2,000 RPM.

Can you explain what happens when you get to 2,000 RPM ? Is that just as high as she will go with WOT or does it falter and die above that? From my experience I know that the "switch" between the idle adjustment and the high speed jet on the carb is right around that area. On mine it would falter and stall when I went past 1,800 RPM. If I moved quickly past though it ran fine at higher RPM. If you try this out of water be careful to not over rev the engine.
In my case it turned out to be the gaskets under the carb by the restrictor like plate. There is a gasket on each side of it.
In was sucking in false air so the idle was way too rich when it got to 1,800 RPM and it would die. Above this the high speed jet takes more effect.

Hope this helps

 

[captmello]

Re: Carb Adjusting and Overheating Issue

agreed, just do the compression test first. Maybe you could rent one at a local auto parts store. Otherwise spend the $30.

 

[JFrog]

Re: Carb Adjusting and Overheating Issue

She begins to falter around 2000 and if I try to go higher quickly or slowly she'll just die.
Will do on the compression tester.
Oh, do you guys happen to know what the point gap should be as well as the dwell angle?
Thanks,
Keith

 

[captmello]

Re: Carb Adjusting and Overheating Issue

Oh, do you guys happen to know what the point gap should be as well as the dwell angle?
Thanks,
Keith

Initial gap is .40mm/.016". Dwell angle is 62 deg +/- 3. fwiw, Don usually recommend getting the dwell up around 62-63. (Don, correct me if I'm wrong)

Here is a link to the manuals

Boatinfo - The library, containing manuals, brochures and other technical documents from the last hundred years!

 

[Alan Lloys]

Re: Carb Adjusting and Overheating Issue

She begins to falter around 2000 and if I try to go higher quickly or slowly she'll just die.
Will do on the compression tester.
Oh, do you guys happen to know what the point gap should be as well as the dwell angle?
Thanks,
Keith

To me it sounds like you have a carb issue with it. The symptom is what I would expect if there is an air leak or you have a clogged high speed jet.
How many turns do you have the idle mixture screw out from the bottom ?
That will help us figure out if there is an air leak.

Also have you done a full carb cleaning?
You can get a gasket kit with new idle screw, accelerator pump diaphragm etc. for around $ 40 online.

My money is on taking the carb apart and clean it out good. Pay special attention to the high speed jet.

 

[JFrog]

Re: Carb Adjusting and Overheating Issue

Yeah, I actually already took the carb completely apart, cleaned out all the jets and replaced all of the gaskets. I have the idle mixture screw 1 1/2 turns out from the bottom.

I haven't set the points up properly as of yet. I replaced them but didn't gap them or set the dwell angle on them. Because I've already cleaned the carb, I'm kind of thinking its the points. I was reading up on point setting and found that if they are not set properly one of the symptoms is the motor faltering and dieing out at rpms above idle.

Nice, thanks for the numbers capt.

Thanks guys,
Keith

 

[JFrog]

Re: Carb Adjusting and Overheating Issue

Hey guys,

I went ahead and did the compression test on the motor and here are the numbers I got. Hopefully I did it right. Anyway:

#1 121
#2 108
#3 106
#4 119

I get this feeling these numbers are bad. Let me know.

Thanks,
Keith

 

[captmello]

Re: Carb Adjusting and Overheating Issue

Those numbers are low. Did you try testing them a second time, with a squirt of motor oil in the cylinder? This helps to tell you if you've got leaky valves, or worn rings. That would be my next move.