Hydrocat 300x handling problem

O

Owen j

Member
Joined
Aug 12, 2007
RO Number
28124
Messages
7
I just purchased a hydrocat 300x (cuddy cabin model). And it seems bow heavy however with the twin 225 (25 inch shafts)yamahas seems to be able to get out of the hole pretty well and at 3000 rpm can easily do 25 plus. Both motors are on Armstrong gill brackets, and are mounted 8 inches below the rear rub rail. Problem is that when going over 4000 rpm the boat chime walks and it gets tot he point of throwing the boat violently back and forth.

In addition the boat has a hard time steering a straight line even though it has counter rotating props.

We measured another Hydrocat and it seems my motors, as compared to the other are 9inches below the height of the other motors. The other was also mounted on gil brackets.

We are thinking that we need to bring the motor heights up, any ideas?
 
My understanding is that the boats were discontinued in 2001. The Hull molds were sold within the last month--so maybe they well-reincarnate. I understand that the early (prior to 1999) were planing boats and better than the displacement hulls (not sure exactly how the hulls were changed).

I own a smaller (25 1/2) planing cat and it does not have any bad handling problems, but does not go quite as well directly into the steeper seas. Even some of the Glacier Bay and World cats seem to have some handling problems in beam seas and down seas. Cats with engines on brackets have to have the engines raised up several inches at least. You want the cavitation plates to run right at the surface. If they are below the surface it will give handling problems. They should be at least 2" above the bottom of the transom if on a 2 foot bracket. Cats run better if the engines are mounted opposite to the "normal" rotation of counter rotating engines. This tends to lift the hulls, and avoid the chine walking you describe. We have added Permitrims which allow us to plane down at lower speeds--11 to 12 knots--one owner claims less than 10 knot still on a plane. The cats cannot use trim tabs on twin engins, so the Permatrims act as tabs, but they must be acting right on the surface.

So I don't know which of those things you will have to change--but the easiest is to put on the Permatrims--not other type of foils. You may have trimed the engines down too much. Trimming up should also help. The Permatrims and moving the engines up will also help. Check the rotation. You want right hand rotation on the prot side, left hand rotation on the right side (starboard). This is the opposite of "normal" boats.
 
Bob thanks, that is interesting since I plan to put new motors on it I will do as you suggest also the planers sound like a good idea.
By the way I spoke to the owner/builder and it did not sound like he had sold the molds yet.. He did explain that since my boat was a newer version the mounting brackets were 9 inches lower.. He also told me that I would need to "lift the bow" with the trim and tilt and that as you mention trim tags are not useful. He also told me that they experimented with adding weight to the stern area as they were bow heavy however that did not make much difference.
 
I just checked out the web site and asked for a quote on these (permatrims)tabs. However as compared to others I have seen in the market they look smalller... why do you insist on these tabs, why are they better? Wouldn'e "bigger be better"?
thanks!
 
The Permatrims are aluminum and machined and painted for each brand of engine. Many of the others are plastic. The Permatrims have been proven on both Glacier Bay and Tom Cats, as well as some others. Some Glacier Bays have used one Dolfin for both engines (half on the outer cavitation plate). The owners have found better results with the Permatrims. The Dolfins and some of the others are made to run in the water at speed. With the design of these cheaper fins some of the cavitation plates have broken because of flexing. Not a problem with the solid aluminum fins. The cat should be set up so that the cavitation plate (antiventillation plate) is at the surface when running at speed. So that the Permatrims are running on the surface, not under the surface of the water. There is a place called "Bob's Machine Shop" which also makes some alunimum fins: These are called "True Tracker Stabalization fins--they are cheaper, if this is a consideration--and some cat owners think that are equal to the Permatrims.
 
Thanks this is helpful. The people at Permatrim answered really quickly and seem to be pretty reactive, asking for pictures of the boat and type sizes of the props etc.

I will also check Bob's
thanks!
 
A GB dealer suggested the split pair of Doel-Fins on my cat (not a GB). For $35, what a difference. I suggested it to some others in my owner's group and they also felt the improvement. Not only do we plane faster and come off plane much more level, but the lift helps with chop.

Bob, the quote I just got for Permatrims was around $250 (with shipping). I don't mind investing the money for increased performance, but I'd hate to drill all those additional holes to find only a marginal gain over my current fins. I welcome your input.

Some boat info: 30' semi-planing cat, twin Honda 50's (I won't win any races, but at 17 knot cruise I only burn 3-4 gph total), engines are not counter-rotating. No real handling problems since the Doel-Fins.
 
I would also like to know the difference between the two.
By the way I used to own a 24 foot Manta cat and the boat really was hard to steer I changed motors to counter rotating and what a big difference.

So you have half a fin on each motor, did you try the complete fins as well?
 
OwenJ- If the other Hydrocat has less chine walk and better steering than yours, and all else is pretty much a 'wash'... I think you should address the motor height difference first. If that brings you the desired improvements, well, case closed, unless you want better....

Permatrims, as compared to Doel Fin or any of the other "aircraft wing" shaped hydrofoils do not create drag. That is why they work without reducing top end speed and can allow a boat to plane off at lower RPM's.

Also, they increase bow attitude and reduce porpoising, increase stability and handling and give you better steering response both in calm and rough water situations.

If you understand how an aircraft wing works to provide "lift", the same forces are used with the Doel Fins, Bob's foils and almost every other foil sold in marine stores, cataloges or on the net. They lift the boat (stern) but do so at the sacrifice of some top end speed and fuel efficiency. The Permatrim is not a curved surface foil and does not create lift. It uses the the top portion of the cone shaped prop wash and redirects lost energy back down in to the water. This is energy that is often lost, particularly on catamarans with twins, but also with mono-hulls as well. This portion of the lost prop wash is now directed downward and allows the stern to lift out of the water (reducing wetted surface area) as well as allow for more bow up attitude adjustment.

The Doel fins and other plastic fins or thin aluminum foils do actually flex and vibrate under power and this rapid & frequent bending has caused cavitation plate failure in some cases. This does not happen with the Permatrims due to their heavy thick design and the fact that they are one piece that bolts around the motor leg and across the top of the cav plate on both sides.

The Doel fins were tried in pairs on the 22 and 26 foot Glacier Bays and handling was diminished as opposed to just using them on the outward sides. IIRC, using the Doel fins in pairs increased the bow steer to annoying levels.

Dealer where I bought my cat (ProKat W/A) five years ago, has installed and tested several foils on several models of GB cats. The Permatrims outperformed the Doel fins and all other foils he tried,. The Permatrims not only handled better they actually left WOT speed the same or slightly HIGHER which is the complete opposite of the other foils.

BTW- The Permatrims work just as well on monohulls w/o decreasing and in many cases increasing top end speeds.

He also found that they work real well on World Cats although the service/design professionals at WC have indicated their doubts and have, at times, advised against them for reasons never made clear.

Durability is of no question with the Permatrims. High grade aircraft aluminum with powder coating and all top shelf stainless locking bolts included. These stand up against bulkhead and piling bumps where the Doelfins have torn or otherwise have been permanently marred or deformed. Average DIYer can install in 1/2 hour with simple tools.

I have mine for 5 full seasons, They have dulled somewhat from nearly 1500 hours of run time and other abuse. But I still stand on them without fear of breaking them or the cav plate and I am well over 300 pounds.

I have no connections with Permatrim in any way other than being a long time satisfied customer that has recommended them to numerous other satisfied boaters!
 
Just wanted to correct some information here about the GBs ... the factory installs a pair of doelfins on each motor for the 26' boats. the single fin on each motor is done for the 22' boats.

We have a 26 and we don't have what I would consider annoying bowsteer or bad handling. Perhaps something has changed in other ways that they rig the motors over the years.

By the way - Permatrims nmay work better but we just haven't felt the need to change anythiing right now.
 
Carter Crew- You are correct.

The "single Doel-fin" was adopted by GB on the first generation 22 foot models to correct what was their notoriously poor handling in beam seas. The newer 22 models handle better and are still shipped with the single . The 26 gained better handling with the addition of the 2 Doel fins. My dealer tried to see what would happen with 2 fins on the 22, which produced the the exaggerated bow steer.

The better handling was achieved with the Permatrims, along with a higher top end and less need to trim motors as frequently in varying sea conditions.
 
Gotcha big-e. You metioned the 26's and 22's together so I wasn't sure if you knew. The 26's always have handled quite a bit better than the 22's and aren't as weight sensitive.

I've been following the permatrim threads on other forums and it may very well be a good enhancement at some point.
 
Hmmmm. So, Sherry, what do you think, should we both give them a try? Somebody asked what would happen if instead of splitting one pair of Doel Fins, two pairs were added. For our boat (30' power cat of the cruising nature), it's a mixed review. I split a pair and have been very pleased. Another owner took a sister-ship to the Bahamas for 7 months and used two pairs to help deal with the added weight of fresh water he took along. He had very good luck. A third owner heard of my split pair, tried it, loved it, bought another pair (to make two sets) and hated it.

I don't mind spending the $250 I was quoted for the Permatrims (for my Honda 50's), if it makes a positive improvement. But I'd hate to spend that money (and drill all those holes!) and not see any return on the investment.
 
Kurt - I say if you're happy with the boat's performance don't muck with it :D At least that's where we are. If you were actively looking for improved handling or top end speed, then I think the Permatrims would be worth looking at.

All these cat hulls react differently to things so it's tough to speak to a different design.
 
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