Long time to Plane out

[RyanCG]

First time boat owner, I know I wont have all the information required, and will not get a chance to run it again for another couple of weeks, but thought I could get some input for things to try or look at next time out.
I recently bought a 21' 1988 Donzi Regazza w/ 5.7L 350 4bbl (260 h.p). The engine lost compression in two cylinders first time out, it had previously been rebuilt and was out of tolerance, thus bought a refurbished long block from Rapido Marine (300 h.p). Lake Marina installed new block in the boat, put a 3 blade 19 pitch aluminum prop on boat. OMC cobra outdrive has a "whale tale" hydrofoil on it. Marina also installed new gimball bearing in outdrive, boat shifts very easily. Engine idles nicely around 500 rpm. However, it seems to take a long time to get out of the hole (10 seconds) until it will plane out (had 6 ppl in boat). When under full throttle trying to plane, the engine is only going up to around 3300 rpm with drive all the way down (kind of seems to bog down), after on plane, the engine will go up to 4000 rpm at WOT with outdrive all the way down. It will go up to 4200 rpm when i start to trim the drive up (@ 45~50 mph per boat speedo), but I can not trim up very far at all until the boat starts porpoising. The Marina had test drove it after engine install and did a timing and carb adjustment and told me it was good to go. Seems like I need to lower the prop pitch or go to 4 blade to get out of the hole, yet the WOT rpm's seem low, so not sure that this is just a prop issue.

[Last Tango]

Well, I will take the first crack at this for you. 6 folks is a lot of people to expect the boat to plane out quickly, especially if you have a full tank of gas and lots of personal gear on board. 10 sec actually sounds about right, maybe even longer. Trim tabs in the down position would be very helpful, but I am guessing your boat does not have them.
4400-4600 RPM is about the max for that motor under the conditions you have described above, even under the best of conditions. Fuel at the gas pumps these days has up to 10% ethanol so the power just isn't there anymore. Hot day would have made it even worse.
This all sounds like bad news, but from your description of the test run, your motor performed right on target for the boat and prop you described. A 3-bladed 21 pitch stainless steel prop might get you out of the hole better with a full boat - prop testing is definitely in order.
Your boat will definitely be very sensitive to drive trim inputs with that wing. Only very small amounts of in or out trim will ever be needed since the wing multiplies the effects.
Make certain that the drive is trimmed all the way in (down) for climbing out from idle to plane. As the nose starts to settle, give the drive trim just a touch up trim.
Your motor sounds like it is new, and it may take ip to 20 hours for it to break in. Full throttle runs are not recommended until you have run it in the mid-range with varying throtlle settings for several hours. You may discover the boat is far more lively when running without a lot of fuel or people. The heavier the boat, the more hull in the water even when on plane, and therefore more drag, which means slower top speeds.

[MOP]

If you are running through prop exhaust a drilled prop will help quite a bit, they do almost nothing with through transom exhaust. Either 3 or 4 blade will look like the photo below.

[mrfixxall]

listen to mop, a 2+2 turbo is probably the ticket. i would first have your marina go through the timing again..thalk to onescubadiver,he has a fasr ragazza and im sure he will share some input about the boat with you..

[BigGrizzly]

I am with MOP on this.