23cc transom rebuild and f350 repower
 

My question is about a 1986 23cc tsunami(tsunami marine) which is kinda similar to the older seacrafts. I am having the transom enclosed with a livewell mounted on the transom, then I will have a bracket installed suited for twin motors, then I will have a single yamaha f350 30" motor installed with all of there new gauges, controls, etc. Would anybody know how this boat will perform or know of anybody that has a similar setup? Any information, ideas or suggestions would be great. Thank you

Re: 23cc transom rebuild and f350 repower
 

At ~ 850# w/prop it's a heavy motor. Add bracket and bait water it's a lot of weight. Post pics!!

Re: 23cc transom rebuild and f350 repower
 

Currently I have a floor livewell and a 2001 250hp on the transom, I am having Hermco do the work and he advised to put a twin bracket for that big single motor, I have seen people with twin 4 strokes from 150hp-200hp on 23 boats and thats gotta be around 1000-1100 lbs right there. I haven't spent any money yet and open to suggestions.

Re: 23cc transom rebuild and f350 repower
 

I have a friend with a 23' Tsunami. It's a heavy foam filled rig for sure. You will have NO problem supporting the weight of a 350HP since Don has recomemnded the double bracket.
I question the big HP as my friends 225hp has plenty of torque and at top end walks away from my single 250HP SeaCraft. I thinks he carries 170 gals of fuel also :eek:

Re: 23cc transom rebuild and f350 repower
 

If 4-stroke is a must, consider that 300 hp Verados and Suzukis are about 220 lbs lighter, and a 350hp racing verado is about 200lbs lighter than the f-350. Are you dead set on the Yamahas? Seems you're losing the weight to hp battle w that motor...

Re: 23cc transom rebuild and f350 repower
 

Chuck, I'm not so much concerned about top end but more about cruising speed around 40 mph through out the keys, crystal river, daytona, and long runs on flat days out of cape canaveral. I like my motor to be big and powerful and running at a lower rpm, plus at times I'll have 8-10 people on the boat with a live well full of scallops or lobster and my current 250 struggles to get up on plane because of the weight. I am a yamaha fan and will continue to support there products(my personal opinion). From what I understand the thrust that this motor is putting out I don't think 200lbs is going to make that big of a difference, not quite sure though.

Re: 23cc transom rebuild and f350 repower
 

Roger that, Capt Mac. Now better understanding your utility, you're probably right, 200 lbs is probably irrelevant. Trusting your power is peace of mind - especially when numerous passengers are aboard. You like and trust Yamaha, by all means stay w/ Yami. Post a picture of your Tsunami. We don't see many out west. Best wishes on the re-power.
:cool:

Re: 23cc transom rebuild and f350 repower
 

http://i151.photobucket.com/albums/s...eys2010365.jpg
http://i151.photobucket.com/albums/s...eys2010332.jpg

These are from the first week of lobster season down in marathon, hopefully next year it will have a bracket and f350!

Re: 23cc transom rebuild and f350 repower
 

Would anybody happen to know how loud the yamaha f350 is compared to my 250 2 stroke? Thats one of my reasons for buying a 4 stroke, I have to turn my motor off to talk to someone at the dock or another boat at nuetral while everybody else still has there 4 stroke motor on. Kinda Annoying...

Re: 23cc transom rebuild and f350 repower
 

Not sure about the F350, but my buddy has a pair of F250s on his 26 Regulator and you can easily talk over them cruising along at 30 knots. At idle you don't even know they are running.

Re: 23cc transom rebuild and f350 repower
 

The f350 is very smooth and quiet at both idle and cruise. If the 23 can handle the weight it will be a very sweet set up.

Re: 23cc transom rebuild and f350 repower
 

I'm not really worried about the weight since I'm getting a hermco twin bracket. I am worried about the performance through choppy seas, I had a friend with the same boat with armstrong bracket and twin 200hp mercs. He said it rode better when the twin mercs were on the boat transom rather then on a bracket. I can't get a hold of the guy and last I heard he sold his boat. Any advice is greatly appreciated.

Re: 23cc transom rebuild and f350 repower
 

That's because he shifted the CG of the boat aft by moving the motors aft by whatever the bracket setback is! It's elementary physics; boat with a bracket will tend to run with bow higher with less of the higher deadrise forward sections of the hull slicing the waves. He may have picked up 2-3 mph at WOT, but I bet his min planning speed also went up!

You SHOULD be worried about the weight of that big V-8 motor! CC's are already a little stern heavy compared to a Sceptre or Seafari, so more engine weight just makes it worse. The big floatation tank of the Hermco twin bracket only helps at rest or at slow speeds. It does NOT eliminate the CG shift when you're up on plane with the flotation tank out of the water! Check out the big block 250/300 E-Tec's. They're quiet too, but much lighter, simpler and cheaper to maintain. My 150 is actually QUIETER than the equivalent 150 4-strokes at 30 mph! It has so much more mid-range torque that it doesn't have to rev up as much for same boat speed.

Your friend should investigate switching to stern-lifting 4 blade props and possibly a Doelfin or equivalent on cavitation plate to improve the ride and low speed planing ability. Those changes on my rig dropped min planning speed from 18-20 mph down to 11-12 mph! Since the 20' hull starts to go airborne at about 20 mph when seas get over about 3', that low speed planning ability makes a huge difference in ride when conditions get real snotty!

Re: 23cc transom rebuild and f350 repower
 

All great points...I think adding a Yam 350 from scratch would be easier. You could adjust the CG by postioning fuel tank and the console further forward. As mentioned, weight is weight...it's the planing speed that would be my concern.

Re: 23cc transom rebuild and f350 repower
 

I know its not a seacraft but I have a 23ft contender and recently put a Yamaha 250 on it.
It needs a little prop work but with the old 225 merc prop she runs 45 mph top speed fully loaded.
The cruise speeds are off due tot he wrong prop but I fine it plenty to push this hull.

No problem getting on plane with 4 adults and 5 kids with lots of coolers and toys we take to Egmont Key for the day.