Aq 125 a

[rossbrown]

I have a 1983 bayliner with the AQ 125A motor. I have installed the hotspark ignition (GREAT MOVE!!!) and changed the propeller to a 15 by 13. It now runs at 2900 wot and does 36 mph. Cruise at 2100 is still doing 30 mph. This is good, but now the water temperature shoots up and the motor overheated. I waited until it cooled and it started and ran back to the dock but now if I go over 2100 it overheats. I replaced the impeller in June and was very happy with the changes made thanks to the input from this forum's members. My question is this; what is the equivalent volvo automobile for this unit? I recall something about a 240 2.1 motor, but I cannot find that thread. I would like to know what is the correct motor for cross reference, as I think I will replace the water pump also, thinking the automotive equivalent is less costly than the 375 dollar marine unit. Any input?

 

[RicardoMarine]

I have a 1983 bayliner with the AQ 125A motor. I have installed the hotspark ignition (GREAT MOVE!!!) and changed the propeller to a 15 by 13.
It now runs at 2900 wot and does 36 mph. Cruise at 2100 is still doing 30 mph. This is good, but now the water temperature shoots up and the motor overheated.

Unless your tachometer is way off, a WOT RPM of 2.9k rpm is going to over-burden and damage your engine.... if it has not already done so.
Over-burdening would certainly cause cylinder temperatures to increase. Not good!


Any of the Marine Volvo Penta OHC 4's can replace this engine.
So unless you are wanting an exact replacement, you'll be better off with more hp.


As for your Hotspark ignition conversion (basically a Hall Effect system), be aware that the conversion does ZERO for any ignition advance that may be incorrect.
Your ignition distributor's advancing system is 28 years old!
See your OEM specs, and then check your mechanical advance against these specs.
The full ignition advance timing marks are there on this engine ..... you just need to strobe them as you increase RPM to the full in limit!
Compare this to the OEM specs.
You may have good hot spark..... but incorrect ignition advance = sacrificed performance! Simple as that!



As for the engine circ pump....... here's info from our member Eduardo:
only the ones for the AQ 131 and AQ151 admit an automotive water circ pump.
This means that, theoretically, an automotive circ pump will fit in any engine model if it has installed a heat exchanger/expansion tank designed for the AQ131/AQ151.

 

[Jerryjerry05]

Just changing the prop by 2 pitches shouldn't drop the RPMs by 1500.
Like Rocadro said.The lugging will cause damage!!!!
Make sure the tach is reading right.
Overheat??Maybe not related???Did the boat run before the changes?How old is the exhaust system?
On the outside on the drive is a hose that hooks to a rubber hose.There is a connector that can go bad.Part#10
It's almost 30 and if the maniflod and heat exchanger is original it's time for a change.
Rebuild the waterpump with a new cam.Again #10.
After 30 years????