I'm working on restoring this great old boat. It's a 1972 23' Uniflite Open Sport Fisherman. The boat was in really bad shape (it's been under water at some point) when I bought it (cheap) and needed a lot of work. It clearly needed complete repower.
The original power was provided by an OMC inboard/outdrive system based on a Chevy 305 block. The engine and outdrive were just trash and I wanted to replace them anyway. I really wanted a direct inboard system. I also really wanted twin engines.
I found a pair of Mercruiser (MIE) 215's for a very reasonable price already set up as inboards complete with transmissions. It's an honest pair of counter-rotating engines. I've had them both running sitting on blocks on the driveway.
...But will these really fit? I've made careful measurements and there is enough space for them (barely). Because this is the open version of the 23' Uniflite it is much (700#) lighter than the cabin versions, so the total weight will be within reason. I spoke to someone with substantial experience (at Padden Creek Marine) and he thought I was on the right track. But, I was still worried that I would be shifting so much weight forward that the boat would be down at the bows. (Might be pretty exciting running home before a following sea with nearly empty tanks.) Before I made major changes I wanted to test the balance of the boat with the weight of the engines in the new location.
I hope you've found my web page useful (or at least amusing). If you're also restoring an old fiberglass boat I'd like to hear from you.
Please remember that I'm not advocating or recommending that you take any course of action. I'm just describing my experiences. I will not accept any responsibility or liability if you injure yourself (or someone else) working on a similar project. I'm not a professional boat restorer. I have no affiliation with any company mentioned on this web page except as a satisfied customer.
Cheers,
visitors since 15 September
2001
So, as soon as I had the bottom of the boat patched and painted and I got the trailer rebuilt...I hauled the boat to the local lake. The boat is just an empty hull, but it will let me see how it floats in the water.
Launching it was actually pretty difficult. In retrospect I can see that without the weight of the engine in the stern, the back of the boat floated so high in the water that it pushed the bow down into the trailer.
With no weight or ballast (just an empty hull) the boat floats remarkably high in the water. This is a very heavy fiberglass hull, but it still floats more than six inches above the designed waterline. Besides that, the hull floats with a distinctly bow-down attitude. Clearly the center of buoyancy is aft of the center of gravity of the empty hull.
In fact, the empty hull rides so high that the corners of the transom are out of the water. It was interesting that even with the very small chop on the lake that morning the motion of the boat was quite unpleasant. It bobbed and weaved like a cork. Obviously not the appropriate condition for a boat that you want to take offshore in the Gulf of Mexico.
The actual balance test was to pump water into tanks in the hull. The tanks were located to mimic the intended location of the new engines. The weight of the water approximated (almost) the weight of the engines and let me see how the boat will float with twin engines installed as direct inboards.
In this picture you can see (just barely) the ballast pump connected to a through hull to draw water from the lake and pumping into tanks located below the sole of the aft cockpit.
I finally pumped 160 gallons (a little more than 1300 pounds) of water into tanks in the boat. The tanks were located in the new (proposed) location of the engines.
The added weight has clearly improved the trim of the boat and it floated almost level. It also drastically improved the way the boat rides in the water. At this point the motion of the boat was far more comfortable than when it was empty.
The most exciting part of this test is that adding weight at the location proposed for the new engines changes the trim of the boat from bow down, to stern down. This isn't as much weight as the engines will be (the engines weigh about 1900lbs) but as water was added the stern continued to lower in the water. As the boat is pressed further into the water from this point the center of buoyancy will shift forward, so additional weight will shift the trim further aft.
