Need Advise : Flat Bottom + V Seaworthy ?

Curious why you went with the 75hp Yamaha over the 70hp Yamaha. Yes, you give up 5hp, but you also lose 109lbs. The 90hp weighs the same as the 75hp.

F90 366lbs
F75 366lbs
F70 257lbs

Just wondering...

 

We didn't had the choice, only 2 of these were available.

We bought this new engine in the price of 50HP engine, it was a bargain.

People here are somewhat idots, they don't believe in 4Stroke OBM, but I think they are the best investment one can make.

 

Dear sir,

you have given us valuable advise, Please provide us more assistance as our nightmares are not over yet.

We have kept our 20 HP engine as a spare for our Wellcraft Eclipse 18' powered by 1983 Suzuki 2 Stroke 140HP OBM. The boat runs fine and has served us very well in heavy seas upto 15' swells.

The little boat we bought was re-powered by Yamaha F75 4 Stroke motor but has some serious stability issues.

Problem # 1
The stern digs in if we don,t put all the load at the bow.

We took it out for a test ride, came on plane at 3800 RPM @ 19 Knots and shakes the hell out of us.

Problem # 2
Over 20 knots it just skids over water like a wild ***.

Test Run
@ 5-7' Swells, We meet the waves head on it manages to clear them but scary ride, while we were crossing a mega container ship in the port channel the swell suddenly became unpredictable, we turned back (under the supervision of pilot boat assisting the ship) and now the waves were at our stern side, we rode a couple of them but one caught us from crest and down and the boat leaned sideways and almost overturned the boat, our captain handled very well then and we were saved from capsizing.

Now we can really understand what you were talking about, please give us suggestions.

We now have an option of swapping the boat with the following.

25' Shallow V Hull, with 18" gunwale, 5'6" beam, 12" Draft, Dead weight 700 kg
or
21' Deep V hull with 24" Gunwale, 6'6" beam, 18" Draft, dead weight 1100 Kg

Please guide us a viable option with respect to our 75HP 4 stoke engine.

 

Bingo,

Adding 7' to your 'unstable boat' is not all you need to do.

You need to determine your real cargo load. You need to determine what you will really do with this boat?

Why do you give multiple examples of your 'captain' almost losing your boat, and yet you say he handled well?

Not safe handling of the boat was your biggest problem .... Your 'captain' needs lessons .... IMHO. Crossing too close to a larger vessel violates basic seamanship .... IMHO. Going too fast for the conditions is another problem ....

And we need pictures!

The 25 footer is going in the right direction, but maybe still too small?

Maybe a 25' to 30' powered catamaran?

Or, a 35' plus monohull?

 

Our captain is a little too adventurous, we think it was his fault but in the end it was the same guy who made the right decision and averted the disaster. Done is done.

Yes they do have catamaran 26', 32' & 52', We tested 26' and liked the stability. I will get some pictures of all the boats and upload them tomorrow, but I don't think F75 will give it enough power.

 

This will be a diving & trolling boat loaded with
4 divers with complete gear & twin tanks
Occasionally, 1 Portable compressor or hookah diving system ( when we take compressor we take along only 4 tanks)
Dive Scooter & Photography Equipment
(Built-In Ice Box)
Snacks / Food - We never had lunch on water
20 Ltr Water
80 Liters of Fuel
And estimated catch of 40-90 Kg of catch on avg trip

 

He still needs lessons ....

You know the 32' or 52' will give you better stability for diving. You will also get better load carrying ability.

It is not just the weight, but the draft that comes with the weight. A shorter boat will get 'sluggish' and not handle rough conditions as well.

The 52' would handle crew and 6 divers much better.

75hp, won't drive a 52' cat at 20mph. Maybe 10mph .... ?

Depends on the hulls on the cat, and your final weight. And your target velocity?

A good catamaran will reduce your angle of attack, so the boat will usually ride better.

Less seasickness .... less speed, less seasickness ....

Do you need 20 knots, or would 10 knots do?

 

we require at least 18 knots and launch the boat from sandy beach ...
A bigger boat will mean more weight and problems while lowering.

Please view the attached picture and advise if this 26' will suffice.

 

Bingo

Bingo: i want to know what hull style or manufacturer of your boat? i intend to build an amphibious hull with this shape and recess wheels in the skegs at side.what does it weigh loaded?

 

They call it catamaran, its manufactured by Marina Sea Craft (http://www.marinaintl.com/index_seacraft.htm)
It weights approx 1200 Kg, I'll take detailed pictures and send on your email.

 

Their recommended cargo is 2500 kilos? Is this the boat? http://www.marinaintl.com/Catamaran%209x28.htm

You need about 1000 kilos?

Much better than the previous boat, don't you think?

How does this boat handle the waves? Will they let you do a test run?

Load 8 larger men (with life jackets) plus your two man crew. Your weight will be a little lower than your mission weight. But, it should tell you if the boat handles well.