Re: Limited to 9.9hp
I've been using an extension that requires you remove the tiller grip and replace it with an aluminum grip with a fitting on the end that accepts the extension. It makes almost no difference with the 9.8hp on either the 12, 14, or 16' hulls.
I really wish one of these had a 20" transom because I found a super clean 1991 Evinrude 9.9 that's been converted to 15hp with a stainless four blade prop already on it.
I may buy it and see about converting it to a short shaft. I know I can use a bracket to raise the transom but that's more weight.
I'm not sure if I'm describing what's happening with the 9.8hp correctly?
When I hit the throttle to take off, there's a huge whoosh of water behind the boat and the boat drops about 12" in the stern and doesn't come back up till I let off the throttle. While sitting still, the hull is sitting with about 4" of the transom below the water and the bow is barely in the water. Without me at the stern the boat is about 2" higher in the water. It takes the weight very well.
The 16' hull sits much deeper in the water with me at the controls, maybe 8" or so of the transom is in the water.
If I tie the bow to the dock, give it throttle, I get the same results, its as if the boat is dragging an anchor.
Now, with the 12' hull, the 9.8hp does the same thing and it struggles to move the boat, yet with the 6hp it moved the boat right along, although still not on plane. With the 12' boat I only ran it with tiller extensions.
What was scary was how low the stern dropped in the 12' boat, even with the neighbors 120lb son at the controls, it dipped low and took on water over the gunwales. At least the Starcraft doesn't take on water. The Duranautic almost sits still before starting to move. I've gone so far as to take a long level to verify for myself that the prop angle in relationship to the hull was correct and what I find is that in the 3rd hole, the motor's AV plate is dead level with the bottom of the boat. The forward two positions should in effect push the bow down. The last three raise the AV plate above level, none of the holes raise the prop out of the water.
The bottom of the hull is glass smooth, I even waxed the hull before putting back on the trailer last time. There is nothing on the hull to hold the boat back. In comparison, my buddies 16' Mirrocraft is loaded with junk, four or five tackle boxes, cans of lead sinkers, two batteries, oars, two trolling motors, and our weight and the 15hp motor moves that boat along between 9 and 12mph on the river. This 9.8 won't move the boat more than 4 mph at best running with the current with no wind.
If it wasn't evacuating so much water from under the hull, I'd suspect a bad prop or hub but both are fine and the prop is moving a ton of water, the boat just isn't moving.
Things like motor depth, and hull shape don't even come into play for this.
Something I should also add is that the first time I took the 14' boat on the lake I also wanted to test a few used trolling motors I had, so I took along four Minn Kota 3hp trolling motors and two group 72 batteries, without a gas motor on the boat.
I tested each motor for about 20 minutes, any one of those trolling motors moved the boat along better than the 9.8hp.
For kicks I hooked up all four and the boat was way to fast for the size of the pond we were on at the time. If a 3hp trolling motor can move the boat along at a satisfactory speed the fact that a 9.8hp gas motor can't.
The trolling motors all have OEM props and prop height was set to 4" below the surface due to the shallow water and stumpy nature of that pond. Along with the weight of the trolling motors and batteries were myself and a buddy who weighs about 260lbs.
