TOPIC: Top speed

What should I see for a top speed on a light 15 foot glass runabout with a Big Twin 35? Just finished a redo on it so the bottom is slick, the motor is healthy and a new 13" pitch prop. Best so far is 28.2. I ran it a couple years ago with a Mark 55 and saw about the same thing. Got a Mark 58 to try next, but I don't expect much more. Looks like it's a 28 mph hull, or do I just need to add another 20hp?
mb

Some hulls are just really happy at 28-35 MPH.
It would probably turn into a lot of cost & effort to break the sound barrier, and sometimes, this chase can result in a pretty dangerous situation - not to mention that the significant other probably wouldn't want to ride any more.
doc

I've been on that chase before, usually cost about a thousand/ mph. It's a boat from the early 60's and I'd like to keep it period looking. The trouble I've seen is that the higher hp motors from that era are really heavy. Looking for another 6-8 mph at wot, and to be able to ride at around 30 with out working the motor so hard. Any 40-60 hp motors from that time that are in the 150lb range?

Flying Scott triple. 60/75hp. Going to land complete around 165lbs. Although I think the 75hp is rated a tad north of what it really is.
They look super cool too (I think). Easy and many 'correct' color options for the cowl.
On the downside MUCH harder to find a complete motor, parts though available harder to come by as well. Not as easy to work on as an OMC but a tad easier (again my opinion) than a Merc.
my .02 cents.

Pay no attention to the doc and his photoshopped pictures....just kidding.
If you happen to have an extra high hp motor sitting around why not?
Here's my 1958 15' Tomahawk with a 135hp Evinrude. Little heavy on the back side at rest but topped out just shy of 60mph (GPS). Handled amazingly good with a little torque steer to starboard.

PS. That's "Dr Go" in the background with his Admiral.

When I was trying to jog my old memory for older vintage outboards that was not quite so heavy ( like Dads '60 Evinrude 75 fat 4) ...I had forgotten about the Scott line. I think Minnesotafox has a few for sale near southeast Mn. Might be worth a contact to see what he has. He has knowledge of this line and has th McCulloch featured for November of this year's fiberglassic calendar. Maybe he would have 2...a runner and a full parts motor for backup? Just thoughts. Cal - forgot how much hp you had on your "sleeper" hot rod. That is some big speed! I am just now noticing Cal never puts the hp rating back on the hoods of the restorations... clever! With any boat we play with to get more sped - each hull has its own characteristics when approaching squirrelly, so I added a kill switch tether to my old motors that did not have it built into the throttle since I may not be as talented driver as others. Doc's looks like the "Ninja" blender turning water into a mist to re-humidify the dry air. Good luck chasing affordable speed!

Here is a nice 65 HP Merc I've just finished updating the maintenance on and gave it a cosmetic restore.
doc

Doc, very nice display you have ,wish I had that 65 merc.

Something to think about when questing for speed. The top end of a planing hull boat is not solely a function of horsepower. It is a combination of hull shape, hull length, beam, and boat weight. Also HP, prop size and type and rpm's. So upping the HP by 20 HP my only gain you 2-3 mph and suck a lot more gas. Cleaning and waxing the bottom and fairing it so the planing surface is fair and true may gain you the same with a lot less expenditure and far less gas consumption. Trying different props may also gain you those few extra mph's. Also putting a much higher hp engine may just exceed the boat's handling characteristics and make it dangerous, prone to chine walking, spinning out and other not so desirable things. If you really want to go faster you need a different boat.

Read and believe Ike's post. Totally agree.
Great input there.