45’ 1970 prop suggestions

[Hookedup2407]

Anyone know how much a 1970 45’ weighs fully rigged with 6v92s 550hp? I just had one fail sea trial. I’m guessing she may have been over propped 26” x 30 4 blades were on her.. & she would not turn up. Twin disc 1.71:1 gears. Doing a basic search i see 24000lbs for a 45 but that seems light.. anyone care to share what what size wheels they had with a similar reduction please chime in. Trying to use a prop calculator without a weight proves to be difficult lol.. thanks in advance Chris

[bostonhatteras]

my boat is hull 350c 1970 45 with 871N with N80 injectors advanced cam timing 500 hours since inframes. Wheels are 27x30 4 blade. engines make 2300+ boat weighs 37,000 in the slings with half fuel full water. I truly believe these boats can get overweight real fast when owners have two sets of china aboard, oil change systems, three seasons of clothes, rugs on top of carpets, every spare and used part the boat ever saw I've rafted up to a 69 45 that sat nearly three inches lower in the water than mine rub rail to rub rail, that was eye opening.

[madhatter1]

Our 46 was just in the slings. 46K with 3/4 full main and full keel. Maybe 1/3 water. No way on 24K.

[bostonhatteras]

Perhaps you found gross tonnage? Thats not a legitimate measurement of a recreational boats weight, it's a measure of interior volume for commercial purposes on big ships. No prop calculator agrees with what my boat does in the real world. BTW 1.5 reduction Allison M gears

[Hookedup2407]

my boat is hull 350c 1970 45 with 871N with N80 injectors advanced cam timing 500 hours since inframes. Wheels are 27x30 4 blade. engines make 2300+ boat weighs 37,000 in the slings with half fuel full water. I truly believe these boats can get overweight real fast when owners have two sets of china aboard, oil change systems, three seasons of clothes, rugs on top of carpets, every spare and used part the boat ever saw I've rafted up to a 69 45 that sat nearly three inches lower in the water than mine rub rail to rub rail, that was eye opening.

Thanks for that.. similar wheel size to what this one had.. i was ready to buy her until we sea trialed (yes the bottom was clean). Hull is in great shape (they sure don’t build boats today like they did back then.. I’d assume 40k lbs would be a safe bet for a prop calculator.. it’s a bit of a project boat. Last owner got 3/4 of the way through Re fitting and stopped so the price is good but the list of things to do is long.. wanted to make sure she was mechanically sound. Engines fired right up with a puff of smoke that cleared within a few seconds. Sounded great, but wouldn’t turn past 10kts.. the 6v92 were installed in 2002’ and appear to be in good working order.. the seller has a set of 25”x27 he’s gunna throw on.. we will see what she does next week.. Thanks Chris

[Hookedup2407]

Perhaps you found gross tonnage? Thats not a legitimate measurement of a recreational boats weight, it's a measure of interior volume for commercial purposes on big ships. No prop calculator agrees with what my boat does in the real world. BTW 1.5 reduction Allison M gears

Gross tonnage is 21GT. A few google searches have me 24k lbs which raised an eyebrow.. I figured she weight at least 30k but I’m just guessing.. I’m using a prop calculator on boat diesel

[jim rosenthal]

My 36C, also built in 1970-71 period, weighs about 21,000 pounds. I think that your 45, would at least weigh higher than 30,000, probably even more than that.