23' CC with Suzuki DF175

[SeaPlusPlus]

Been toying with an idea, wanted to get some opinions.

I have a 2008 Suzuki DF175 25" on my 20SF with pretty low hours. My 23 that I'm restoring does not have power.

I'm thinking about moving the DF175 to the 23' and if I'm happy with it, picking up a similar year DF140 for the 20SF.

Now I know the general consensus is 175 HP is under powered for the 23, but here are my reasons for considering this:

• Trying this will basically be free, it's out of warranty so I'll be doing the moving/rigging myself.

• I already have a second set of controls/gauges for the DF175 (had planned for a second station on the tower in the 20SF that I never installed) so no need to buy a binnacle, tach, etc or spend hours derigging/rerigging my 20SF if this doesn't work.

• Need to do more research but just about everything I have on the 20SF tach/control wise should just hook right up to a DF140.

• The DF175 is a lot of motor for the 20SF, she would perform just fine with a DF140 (as proven here) and would benefit from a lighter engine on the bracket

• Bigshrimpin has proven that a 150 HP power plant will perform admirably on this hull

• I think a DF140 will be easier to sell on the 20SF than the DF175

• If it works it will save me a boatload of money, if it doesn't I just move the motor back to the 20SF and get a similar year DF250 for the 23 using the same binnacle/tach

I'm not looking to go 50+ mph in this boat (did plenty of that in the 20SF), just get from A to B safely and efficiently.

Here are some numbers I've been running, first the estimates:

Full restored weight (with the DF175) around 4476.4:



And that 2323.1 estimated restored hull weight number comes from this estimate on composite vs original and removing the liner (which I am making a guess that its around 300lbs):



Take that full restored weight and add 500lbs of persons, 100lbs of gear, 100lbs of boat jewelry, and 50 lbs of ice to give a fully loaded weight of 5226.4lbs.

Plug that into a calculator using Crouch's formula to give a max theoretical speed of 46mph (using a constant of 250 for "Fast V bottom High Drives, boxes, notched transom, good bottom"):



I currently have a 3x16x23p prop on the DF175, plugging that into a Prop Slip Calculator with 9% slip and I'm seeing the same max top end speed at 5700 RPMs:



These numbers seem to align pretty well with Bigshrimpin's numbers who saw 38 mph WOT at 5700 rpms on that 150 HP, and I'd be happy with top end in the low 40s and cruise in the mid 20s.

In my opinion I'm only wasting my time if I fail right? Even if it works at first and I hate it after using the boat for a while I could still sell the DF175 and repower. My biggest concern is safety in snotty conditions and if the DF175 has enough umph to push the boat through the snot.

What do you all think?

[wattaway2]

had an older 200 ocean pro on my 23 a and was able to get 43mph on the gps with it. didnt spend much time with dialing it in but feel like you should make it in that area

[bmajvi]

I'm hoping you'll make the swap and post all the results! Your analysis and plan make a lot of sense to me, but real world results are what count... FWIW, I was an early Zuke adopter, when I put a DF140 on an 18SF on 2002, because I got a sweet deal on the motor and couldn't find a Yamaha 115 when I was ready to pull the trigger.

[hobiekanobie]

I have a 2004 DF140 on my bracketed 20sf and would happily replace it with the same engine. Typical outing for me is 3 adults and 2 kids, 30gals fuel, full cooler plus snacks and I get roughly 3mpg with an engine that is mounted too low...

[wattaway2]

In your calc’s don’t forget to include ice for the cooler you and your crew and miss. Stuff ect

[SeaPlusPlus]

Originally Posted by wattaway2

In your calc’s don’t forget to include ice for the cooler you and your crew and miss. Stuff ect

Yeah thanks for the reminder! I did factor all that in though to get the estimated 5226.4 fully loaded weight.

Originally Posted by SeaPlusPlus

Take that full restored weight and add 500lbs of persons, 100lbs of gear, 100lbs of boat jewelry, and 50 lbs of ice to give a fully loaded weight of 5226.4lbs.

[FLexpat]

I am thinking you would be fine and you have nothing to lose besides the time for a swap. My 23 Sceptre originally came with a 233 Mercruiser I/O. I seriously doubt that clunky 351 2bbl ever got much above 215 at the crankshaft, no way did it get very much at the prop. It weighed about 600 lbs more than the Zuke and the pre-Alpha drive was mounted WAY deep. We played with props a bit but probably not enough and prop tech was not too advanced then. Still got ~35-40mph WOT and comfortably cruised about 25-28. If it gets snotty you won't be going fast so you won't need much HP to run about 15mph and you could probably stay on plane at 12-14 with the light OB.

My calcs say that it takes a bit over 110HP at the prop to get a light/normally loaded 23 on plane (maybe less w an OB) and probably just a bit more for a comfortable cruise.

I would run Crouch's with a constant of about 230-240 with that setup though.

[77SceptreOB]

Although I'm not a fan of underpowered boats and have commented so on other similar threads, I do believe your scenario will work satisfactory for your stated expectations.

From a historical perspective we have run our 1977 23' Sceptre with a 200hp Johnson from 1976-1979 and an Evinrude 200 from 1980-1988. In both cases the boat performed fine in offshore and inshore use. It never seemed sluggish even when loaded pretty heavy. I also don't think either one of those engines were actually over 200 hp at the prop and probably significantly less during that era.

A few years ago, I had a plugged carb on my Yamaha 225 and was effectively running on 5 cylinders thus netting out approximately 185hp. During this time the boat still performed fine. In fact I didn't even know I was a cylinder down because the boat would run 37 mph at 5100 rpms and still had a decent hole shot with a 17 pitch prop. I ran it this way for approx 50 hours before the carb issue was discovered during a "tune up". After the carbs were rebuilt and synchronized the boat ran 43 mph at 5800 rpm. That was much improved, but proved at 185 HP even over propped the boat ran pretty good.

[Bigshrimpin]

It'll work fine. The 150 Merc is a beast in slop. I ended up with a 15P enertia and I tried a bunch of props. The 175 zuke has a different ratio lower, so just be sure to prop the engine to hit Max RPM's.

Here's a thread on THT from CANARIANFISHER. He's running a 175 suzuki on his 23 seacraft. I'm not sure which prop he's has, but his boat hits 39mph WOT.

https://www.thehulltruth.com/boating...e-model-7.html

[DonV]

OK Jim, I see the Mega Millions was won in SC, you can now go out and buy a new engine with your winnings!!