Bow Rise question - Zodiac Hurricane 733

[Otis K.]

Hey guys, I have been running a Hurricane 500 for the past 10 years up here in Alaska and i just bought a Hurricane 733 from the U.S Coastguard in an auction. I have been looking for a 7m RIB for a long time and finally found one and i am very happy with it.

It is the 200hp Inboard Turbo-Diesel Version. (Volvo TAMD41-A) The entire transom is completely reinforced by stainless steel and has towing brackets and rigging mounts all around. The Boat is very heavy, i estimate it to be in the 6000lb range. This Boat was used for towing, freighting & rescue for the U.S Healy Ice-breaker up in the Arctic up until spring 2016, the GPS still has thousands of Nautical miles of data recorded North of Iceland and the Chukchi sea, pretty awesome..

Anyways...

One thing i noticed with this Rib however is that the Bow-rise is a little high and the the boat does not completely plane until i am at the 3800 Rpm range which is to high for this motor to be run at. The outdrive is trimmed down as far as it can go @ -4 trim. I was thinking about installing trim tabs but am unsure if the bow is supposed to be elevated like this. The Helm and Console are huge and are both located at the stern so this does not help i imagine.

I do however plan to purchase 6 15 gallon fuel drums to tie down at the bow, maybe a couple hundred pounds on the bow will help a bit?


Do any of you have trim tabs on your ribs?

[tworotorturbo]

Good find! Any pics? Is the motor in the middle of the boat, and on a jack shaft setup?

Thats the same motor that was in my 7.4 Searider. Whats your top speed at 3800 RPM?

[beamishken]

I've seen plenty of ribs with tabs on and they certainly help on a hard boat so I'd say they should help with your problem.
I'd be trying to move weight forward rather than adding more weight if you can unless you require the extra fuel for increased range

[Otis K.]

Originally Posted by tworotorturbo

Good find! Any pics? Is the motor in the middle of the boat, and on a jack shaft setup?

Thats the same motor that was in my 7.4 Searider. Whats your top speed at 3800 RPM?

The Motor is located at the middle of the Rib, which i looked up the specs of the Volvo Tamd41-A and the dry weight of the motor is 1100lbs (Not encluding outdrive, shaft, 5 gallons of oil 5 gallons of coolant etc) It has a indeck 50 gallon fuel tank in front of the engine towards the bow so i thought that would be good for weight distribution but bow is still riding high.

The Rib also Porpoises on 2-3ft rollers as well, i just needed to know if it was unheard of to install Tabs on ribs and apparently it is not so i think that is what i will do.

It is definitely not a speed boat, with a 15x19 prop WOT=30mph Cruises about 23 mph. The motor is rated for a WOT of 3800rpms and i am reaching 4100 rpms with current prop so i think i can squeeze a little more but i want all the power i can get because i usually travel heavy.



Cant get images to attach to anything i post for some reason.

[Otis K.]

Originally Posted by beamishken

I've seen plenty of ribs with tabs on and they certainly help on a hard boat so I'd say they should help with your problem.
I'd be trying to move weight forward rather than adding more weight if you can unless you require the extra fuel for increased range

Yes, i need the increased range so the 15gallon fuel drums on the front is a must.

[Otis K.]

i posted 3 pictures of the rib in my album.

[Bigtalljv]

Yes, trim tabs are common on the 7m boats.

What's the angle of the deck when you are sitting still Vs underway? I remember measuring mine for radar and they were pretty similar but I couldn't give you the number. iPhones have a quick and easy level. Swipe right at the compass.

Jason

[Otis K.]

Originally Posted by Bigtalljv

Yes, trim tabs are common on the 7m boats.

What's the angle of the deck when you are sitting still Vs underway? I remember measuring mine for radar and they were pretty similar but I couldn't give you the number. iPhones have a quick and easy level. Swipe right at the compass.

Jason

It sits pretty even in he water, it looks great. No part of the tubes even touch the water and there is a good 4 inch space between.

Cant get pictures to attach to my post i have some

I posted a picture in my album of it sitting on the docks, i think it is pretty well balanced.

[tworotorturbo]

I looked at your album, sweet looking RIB!

Whats your outdrive, single prop? Does it smoke when throttling up?

[Otis K.]

Originally Posted by tworotorturbo

I looked at your album, sweet looking RIB!

Whats your outdrive, single prop? Does it smoke when throttling up?

It is a single prop Volvo Penta 290 Outdrive.

The engine smokes a lot when starting up cold and continues to smoke until its temperature reaches 130 degrees, which i can't get it that warm without running it in the 2000 rpm range. So Its a little embarrassing to smoke everyone out at the harbor, but i really don't care to much... a little smoke can be classy haha. Once the engine is heated up though absolutely no smoke for the rest of the trip, i can even shut her down for a couple hours and it holds its heat and she fires right back up with no smoke what so ever.

Great running engine overall, always starts within 3 revolutions cold in -10 using the GlowPlugs & she sounds like not even one revolution starting up warm.

I have done a lot research and i guess White/Blue smoke at cold startup is very common for the 41-A's.

In the newer 41-B's & 41-D's smoking was apparently corrected by an exaust butterfly valve in the 1990's but the engines do not have Glow Plugs like the 1980's 41A's.

I start my engines in below 0 temperatures in winter and glow plugs are priceless and worth much more then a little smoke at start-up. So i am happy i have the 41-a

[beamishken]

Your info re smoke at start up is exactly right. Have you checked the tacho with a shop tach as they can be inaccurate?
Iirc those engines are max rated at 3600? so maybe it's hitting the governor,you can do a high idle test to see if it is sitting on the governor. If it is it could be it's underpropped,either had the wrong prop fitted or been propped for very heavy loads.You would expect a little black smoke under hard acceleration so maybe the engine isn't seeing much load.
Correctly propped you should still be able to pull over 3600 at wot with a normal load & should run under max rpm (I think 3400 is max continuous rated speed?)
You need to be careful if you start switching props that you don't end up over propped which is worse than under propped

[Otis K.]

Originally Posted by beamishken

Your info re smoke at start up is exactly right. Have you checked the tacho with a shop tach as they can be inaccurate?
Iirc those engines are max rated at 3600? so maybe it's hitting the governor,you can do a high idle test to see if it is sitting on the governor. If it is it could be it's underpropped,either had the wrong prop fitted or been propped for very heavy loads.You would expect a little black smoke under hard acceleration so maybe the engine isn't seeing much load.
Correctly propped you should still be able to pull over 3600 at wot with a normal load & should run under max rpm (I think 3400 is max continuous rated speed?)
You need to be careful if you start switching props that you don't end up over propped which is worse than under propped

What you are saying is pretty consistent with what i have learned. The boat came with a 16x13 towing prop was was turning 4500rpm at WOT under load. I changed the prop to a 15x19 prop and now it turns 4200rpm under load.

What i learned from browsing numerous marine diesel forums is that the
TAMD41-A is rated for 3800rpms @ WOT with a max Cruising rpm @ 3400 as you stated. So currently i am under-propped by 400rpms if my tach is functioning properly.

I am thinking that i want to keep it under-propped so when i load it down with 150 gallons of fuel, Gear, Dudes, Beer and a Moose i can still have plenty of power to push me over waves.

I actually think it might be easier on the motor if there isnt much load on it and you dont cruise above 3400rpms

[beamishken]

Yeh exactly what I'd say only thing left to check is tacho which is an easy check

[Otis K.]

i appreciate the info guys, i have my first Bear & Deer hunting trip planned in April. I will also be installing a Crab pot puller on the rib for Crabbing & Shrimping on the same trip.

[Otis K.]

Originally Posted by beamishken

Yeh exactly what I'd say only thing left to check is tacho which is an easy check

Will do Bro, do you have the same engine? has it been reliable for you?

[gtflash]

I think trim tabs are essential on slightly larger boats or boat with a proper deep v. Not only do they help with planning speeds but also correcting for lean into wind. However consider checking for extra weight that shouldn't be aft such as trapped water in the hull, also move anything mobile forward, store all ur junk forward, and try some mobile ballast forward temporarily. Maybe invest in a nice big anchor.

My first boat was a rather flighty regal and I used to carry two 20kg bags of sand forward, cost less than a tenner and on the odd occasions I needed the bow to lift up, I just cut and tipped them over the side.

[beamishken]

Hi I don't have the same engine but have worked on a few
There a prety Hardy engine and are known for doing high hours no problem if cared for.
Some think they are better than the later engines with the electronic controls as there's less to go wrong
Their only down side is because their built more like a commercial engine there a bit heavy compared to others about but you can't have everything!

I think I'd definitely check the tacho as I'm a bit surprised the governor would let it rev to 4500rpm I'd expect it to stop the engine at 4200 -4300 ish on an engine rated to 3800 max I may be wrong but it just seems a long way over the rated speed

[jwalker]

Prop it for maximum load so wait until you've got it sorted. However, the engine will not make more power at higher revs so getting it correct and not over revving is important.

I have trim tabs on my rib and wouldn't be without them. My advice is to ensure you have tabs which are long rather than wide. Wide is common so you may have to search them out - I made mine from fiberglass. The reason for length is that the upward lift the tabs provide is more effective the further aft they are and also when you run them flat you are effectively extending the hull length.
If you fit the tabs along the transom V as is common, another benefit you'll have is the ability to reduce the steering necessary when you are fighting a side wind. - When the boat lists on a side wind it will do so towards the wind since you will be steering into the wind to prevent the boat being blown off course, putting down a tab on that side will lift that side of the hull to counter the listing but it will also steer the boat into the wind, a little by drag but mostly because the tab is angled on the transom V and as you lower it you also provide some steering. Of course the result of this is that the tab levels the boat whilst also steering it into the wind. A double benefit.

[Otis K.]

Originally Posted by jwalker

Prop it for maximum load so wait until you've got it sorted. However, the engine will not make more power at higher revs so getting it correct and not over revving is important.

I have trim tabs on my rib and wouldn't be without them. My advice is to ensure you have tabs which are long rather than wide. Wide is common so you may have to search them out - I made mine from fiberglass. The reason for length is that the upward lift the tabs provide is more effective the further aft they are and also when you run them flat you are effectively extending the hull length.
If you fit the tabs along the transom V as is common, another benefit you'll have is the ability to reduce the steering necessary when you are fighting a side wind. - When the boat lists on a side wind it will do so towards the wind since you will be steering into the wind to prevent the boat being blown off course, putting down a tab on that side will lift that side of the hull to counter the listing but it will also steer the boat into the wind, a little by drag but mostly because the tab is angled on the transom V and as you lower it you also provide some steering. Of course the result of this is that the tab levels the boat whilst also steering it into the wind. A double benefit.

I am good on the propping, I am keeping it underpropped in anticipation of loading it down very heavy. This should not be an issue because I do not run this motor above 3200 rpms.

I like your view on trim tabs, but I have already ordered a set of retractable tabs. I think they will be fine on keeping the bow down which is my primary reason.

Eventually though, I think I am going to pull the diesel to free up deck space and weight & have a 3-4ft aluminum pod fabricated for the stern. Probably end up throwing twin E-Tec 225s on it. This is speaking years & years into the future though, just a dream.

[Bigtalljv]

Im not sure underpropped is a good idea. The boat is designed to carry a lot of weight. You'll probably never have enough weight to really load it down. I can't really tell the difference between 2 people and 13 people with a single 250 outboard. The boat is rated for twin 150s When I talked to hurricane during my rebuild they were happy I was staying with a single 250.

A diesel boat is not a race boat so who cares if you're a tad bit slower out of the hole. Prop it for how it runs 99% of the time, at cruise.

Rated payload on your boat is like 2500 lbs. and the boat probably weighs less than 5000lbs empty.

The bow is a big thing. Odd question, how tall are you? My teenagers couldn't drive it until they grew some.

Jason