The GM 3.0 liter (181 ci sounds about right)four is offered as an "industrial" and "marine" engine. For specs and photos, go to gmpowertrain.com. I'm not sure what it may share in common with the "Iron Duke" 2.5 liter. They only sell to OEM accounts, but I would think you could buy one from Mercury or one of the industrial resellers, if you really wanted one.
Be prepared to use your metric/SAE converter.
As far as I know, Mercruiser engines have been GM/Chevy products since at least the 70's. They may have used others that I'm not familiar with. Maybe some of you boaters can speak to that topic.
---> Bill
