[mikeyt]

Yep, ya gotta remember the max prop horsepower the 180 is rated for is 210. Anything over that might lead to transom issues and the extra weight of a V8 will really make your Smart Tabs work to keep the bow down and the stern off the bottom.

[95gts]

Unfortunately a 4cyl to v6 or v8 swap isn't simple or straight forward, the engine mounts are different and so is the upper outdrive, it has a different gear ratio for the 4 banger. As the owner of an 18 footer with a 3L I can say that having two different props will make the boat much more usable. For cruising and light loads I use a 3 blade 21 pitch, for watersports and and an awesome holeshot I use a 4 blade 19 pitch.. 25-28mph is a comfortable cruise speed with the 21 pitch 3 blade, 22-25 is comfortable with the 19 pitch 4 blade.

[ColoradoDiablo]

4.3 will bolt in with no mods to the hull. All you need is the 4.3 motor mounts , and the drive or regear yours.
Buy another boat.

[95gts]

The 4cyl mount is in the front of the engine, the v6 and v8 have mounts on the sides of the engine.. or am I missing something?

[Andy b]

Originally Posted by mikeyt

Yep, ya gotta remember the max prop horsepower the 180 is rated for is 210. Anything over that might lead to transom issues and the extra weight of a V8 will really make your Smart Tabs work to keep the bow down and the stern off the bottom.

Another issue with over powering a 180 is length,
Stability at the top end of my range now (48-50mph) gets a bit light!
Not sure I’d want to go much faster in this boat! I could see it swapping ends quite easily.

[ColoradoDiablo]

The motor mount towers are there , just not used by the 3.0.
Maybe I'm wrong.......it is early.
Why would they manufacture a hull for each engine/drive package? A lot of extra work.

[95gts]

I agree, it's the same hull whether it's a 4, 6, or 8. Mine being a 4 has nothing there to mount the 6 or 8, so holes would need to be drilled in the stringers for the new mounts.

[okhamis]

My Mercruiser 3.0 on Alpha one is definitely under powered for the weight of the Mariah 18 SX,I need to overhaul the engine and I am now considering to upgrade it to a 4.3 V6....from the above thread it seems a straight bolt on right? will we have to do modifications for the exhaust? will the Alpha one sustain the additional power (assuming no modifications to be made on the shaft)

[mikeyt]

As the previous posts stated, it is a fairly straight forward swap from a 3.0 to a 4.3 and the Alpha 1 will handle up to 300 hp which is far more than the 4.3 liter will put our or the 180 hull can handle. You may though have to change out the gearing in the Alpha 1 because of the increased 'grunt' of the 4.3. Personally..... i would just sell that SX18 and buy something with a 4.3, 5.0 or 5.7 in it.

[okhamis]

Thanks Mike.

I did not know the Alpha 1 would be able to handle upto 300 bhp !