Any ECU experts out there?

[mriley]

During the recent best boating weather we've had for years, I've suffered from the incredible frustration of my boat being firmly tied up alongside, with a u/s ECU. The engines are AQ171c, and new replacement ECUs are impossible to find.
I do however have in my sticky mitt a car ECU, from a volvo car with the same basic engine. It looks identical, but has one connection missing. This one of 2 negatives, and goes from the ECU to the negative of the starter relay. All the other connections are present, and go as expected to the timing sensor, distributor, coil and earth. The question is whether the missing connection is really required, or whether the ECU would work without it. I haven't dared to try without advice, for fear of blowing something up. Any advice would be greatly appreciated. Thanks.

 

[mriley]

I should perhaps made clear that the missing connection on the car ECU is clearly by design; although the same plastic socket is present on both on the car ECU it is not pierced to accommodate an electrical fitting.

 

[rafiki_]

Sounds like one for VolvoPaul.

 

[volvopaul]

Try and google a wiring diagram for the engine , it maybe in the the manual, you will then see where it is in the loom. Or trace it yourself on the engine.

A mate has a 27 sun fury in gosport with the engines out at the moment il have a word with him as he has just ought another unit from a car, maybe he has a spare unit. You may find the extra connection is just for marine use maybe an extra earth to the actual unit as it would be attached to the wing or the car which would carry its own earth bonding through the mount screws where on the engine it may have to have its own loop wire fom the loom.

 

[hartcjhart]

try BBA reman they are very good with ecus

 

[Anthony]

My understanding is that the actual mapping is typically different between the car and marine ECUs because they use different power bands between the two applications; I am not so sure of Volvo but I believe Mercruiser at least use different cams becuase of this and thus have different mappings to suit

Anthony

 

[spannerman]

When you say ECU, I guess you mean the ignition module? Is it the type with the coil attached to it or is it different. I have just checked the 171 wiring diagram which shows a Renix type dry coil (square) attached to a ign module with 3 plugs on the top, the diagram shows the black going to earth and the other black as you said goes to earth via the earth on the relay which amounts to the same thing. Reading directly from the workshop manual it says that the single black wire on the 3 pin plug is connected but not used on marine applications.
So as long as the pink +, black - and grey tach signal on the other 3 pin plug are connected it should work, the 2 pin plug is the timing sensor,but as mentioned the timing advance curve could be set up differently so its worth checking with a strobe that you don't get over advance as this will cause detonation and piston damage can result, under advance will give sluggish performance.

 

[Scarron]

Here's a stroke of luck, I happen to have an AQ171 which broke a cam belt (as they very often do) and I haven't got around to selling all the bits yet. I do have all the ignition components left. Afraid I am away on holiday at the moment and won't be back till next Monday, I am only up the road in Southampton. I have PM'd you my contact details

Paul

 

[volvopaul]

Here's a stroke of luck, I happen to have an AQ171 which broke a cam belt (as they very often do) and I haven't got around to selling all the bits yet. I do have all the ignition components left. Afraid I am away on holiday at the moment and won't be back till next Monday, I am only up the road in Southampton. I have PM'd you my contact details

Paul

Hi , a mate of mine in port Solent may be interested in your bits, let the op have the module with pleasure if he needs it, pm me your number if you wish , ill pass it on . Cheers