1998 300 Promax (pair)

[Mhall222]

I am going to have a pair of 1998 promax 300 25" motors for sale soon. One motor has 120psi on all cylinders cold and runs great the other runs but has a knock according to Previous owner. Both motors are fairly clean for their age but do have some corrosion the the mid sections. The lower units look to be fleetmaster units. The cowls are in fantastic shape (dirty) but will clean up and look near perfect. I am going to look into the possible issues with the motor with a knock hoping for something simple but not expecting it to be the case. I am not sure on the hours but I am hoping to be able to recover that data after finding someone with a computer to read the data. I will post more pictures as soon.

Motors are located in Leesburg, GA.

Asking $7000 for the pair as they sit. That price may change after I diagnose the motor with a knock.

[Mhall222]

I found out what the "knock" was one piston was totally melted and the cylinder sleeve is busted up but actually the block looks totally un harmed. There are some marks but I do not see any cracks or anything major wrong with the block itself. The engine turns over fine by hand so possibly there is no crank damage. All the cylinders on the side of the melted piston have some scaring so I would bet a bore and next size up pistons job would be needed.

[Varmint]

Cranks prolly toast too, may get lucky

[Mhall222]

Cranks prolly toast too, may get lucky

What exactly causes damage like this? I would assume a very lean condition but how did it get lean on that one cylinder . The rod bearings on that bent Rod feel nice and tight still. Of course I have no clue without tearing father into it if there's bearing damage or crank damage.

[2jz]

I am going to have a pair of 1998 promax 300 25" motors for sale soon. One motor has 120psi on all cylinders cold and runs great the other runs but has a knock according to Previous owner. Both motors are fairly clean for their age but do have some corrosion the the mid sections. The lower units look to be fleetmaster units. The cowls are in fantastic shape (dirty) but will clean up and look near perfect. I am going to look into the possible issues with the motor with a knock hoping for something simple but not expecting it to be the case. I am not sure on the hours but I am hoping to be able to recover that data after finding someone with a computer to read the data. I will post more pictures as soon.

Motors are located in Leesburg, GA.

Asking $7000 for the pair as they sit. That price may change after I diagnose the motor with a knock.

Pm sent

[Todd D]

look like 20" mids with 5" extension kits installed!!

[Varmint]

water in fuel ?,bad plugged injector,or just plain run hot

What exactly causes damage like this? I would assume a very lean condition but how did it get lean on that one cylinder . The rod bearings on that bent Rod feel nice and tight still. Of course I have no clue without tearing father into it if there's bearing damage or crank damage.

[SUNKIST]

if you part out the bad motor...interested in the ecu's fuel and ignition.

[Mhall222]

I will entertain offers on parting the bad motor but I still think it has greater value as a whole for someone. It seems the cowl is what has most people interest and I assume its fairly high dollar being a fiberglass aftermarket unit is $700. Anyhow, at the moment unless I get some good offers on the parts I want to keep the motors whole.

[Mhall222]

I am planning on running the good motor later today and I was going to build a motor stand but just mounted it to the back of a hurricane deck boat project. I kind of like the way it looks on my hurricane but, I think I will be happy with a 200 on it which I have in storage.

I am going to see about getting the data off these engines, Is it possible to just take the CDI to the Mercury shop and them hook it up? I would rather not take the whole motor to the shop.

[Mhall222]

I started tearing down the blown engine to part it out. You can PM me here or text/call me 229-328-5288 for more info or pictures.

[SUNKIST]

interested in ecu,s fuel and ignition since your partin them out. bryan 703 501 8708 or pm me.

[Mhall222]

The blown 300 Promax has been parted out so only the Good motor remains. This motor has a 20" mid with 5" spacer and a 25" counter rotating lower. $5000 complete or $4500 minus lower and spacer. If the motor does not sell soon I am going to part it out as well. If you have any questions let me know, Compression numbers on this motor cold are 120 across all 6 cylinders. The mid does have some corrosion and areas were the PO has painted over the chipping paint. I do have the standard rotation lower so if you needed that lower I could swap them out no problem.

[Mhall222]

I went ahead and checked everything over well and hooked the engine all up to run it a bit. Dang thing brings back memories from when I had a 300 promax on my back country proguide 201 many years ago. Here is a short vid of the motor running.

https://www.youtube.com/embed/6jr5zFDl680

[PaulCXB2002]

Any trades on the good motor?