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Donzi 24 -2000
Hello guys,
I´m from Sweden and this is my first boat. I don´t know much about boats so I would be grateful for some expert advice. I have a 350 Mag MPI 300 engine on the boat but can only reach around 35 knots(I don´t know what this translates to in MPH). Do anyone of you guys have any suggestions how to make it go faster? I have tried to speak to different "experts" but they all give me different answers and I feel really lost.. Thank you guys! |
Welcome to oso!
Tell us more about your boat and I’m sure you’ll get some good replies. 24’ Donzi…..what model is it? Is the engine strong, good compression, and tuned properly? What maximum rpm are you getting? Is the drive unit an Alpha or Bravo? What propellor and pitch do you have? Many boats in Sweden have antifoul (bottom paint) which knocks off a lot of speed too. More info and some knowledgeable members will jump in. RR P.S. 35 knots is 40 mph. |
Thank you for your reply.
It is a Donzi 24 BlackWidow from year 2000. I can not say if the motor is strong, good compression or tuned properly. Also I don´t know about the Alpha or Bravo, and the bottom color. I have tried and asked the seller but he does not reply. I will try and find someone that can help me answer those questions. The only thing I can answer is that the propeller is aluminum and the RPM on full throttle is around 5000 RPM. I´m looking for some not to expensive fixes to try and make the boat faster. I bought the boat and promised my son that it would go faster then his friends boat but now it is the opposite and my son is very disappointed with me.. I have decided to sign up for a boat mechanic course to try and learn more about boats but the mountain feels high and I´m a slow learner. Thank you for helping me! |
I’m not a Donzi expert but I thought the Black Widow was earlier than 2000. I thought they were around 1990?
Check the HIN (hull identification number) might be on your paperwork, but should be a 17 character number on the back of the hull. Right hand side, just below the gunnel rubbing strip. The last two characters will tell you the year. ‘00’ would be a 2000 model, ‘95’ means 1995 model, ‘90’ means 1990 model etc, etc. I thought most of them were built with an OMC big block engine, 454 cubic inch Chevrolet block, a couple of different versions, 330 hp or about 370 hp. The 350 magnum 300 hp is a good engine but sounds like it may not be the original engine. Doesn’t matter, Mercruiser engines are probably a lot easier for any accessory parts and service in Sweden anyway. 🙂 With the bigger 330-370hp engines, I think they did around 60 mph when new. Speed will be less if the boat is heavy, full of fuel, a lot of gear and people on board or the bottom of the hull is not clean. With most boats that age, there’s also a risk the stringers and transom have water intrusion and the wood inside is waterlogged. That can add a lot of weight to a boat. Did anyone survey or inspect the boat when you were buying it? The aluminum prop won’t help, not sure what size you’d need but a good stainless steel prop will be faster. Driving the boat takes time to learn how to get the best performance. Accelerate gradually with trim tabs down (if you have them) and the sterndrive down (in). Once up and running at 25 knots, you should raise the trim tabs all the way up and trim the sterndrive up a little to lift the boat up and reduce the amount of hull touching the water. Check on the trim gauge while the boat is out of the water, look where the gauge reads when the drive is vertical, that’s a good place to start once you’re up on the plane. You can gradually trim the drive up a little bit more but the aluminium prop will cavitate (slip) pretty easily. A stainless prop will bite and hold on much better. It’s a lot of learning, just go slowly and enjoy yourself. If the boat feels unstable, starts to bounce or react strangely, you’re pushing too hard. Try a Google search for Black Widow 24 speed and you’ll find info on other forums. I’m sure someone else will jump in here too, when they wake up. Most of our oso members are based in America. 🙂 Sorry it’s not as fast as your son hopes but it should be a bit quicker than 35 knots of the engine is running well, it’s not too heavy and you get a better prop. Meantime, remind him that although his mate’s boat is faster, a Donzi is probably a lot cooler. 😎 Good luck, RR |
Originally Posted by rak rua
(Post 4870932)
I’m not a Donzi expert but I thought the Black Widow was earlier than 2000. I thought they were around 1990?
Check the HIN (hull identification number) might be on your paperwork, but should be a 17 character number on the back of the hull. Right hand side, just below the gunnel rubbing strip. The last two characters will tell you the year. ‘00’ would be a 2000 model, ‘95’ means 1995 model, ‘90’ means 1990 model etc, etc. I thought most of them were built with an OMC big block engine, 454 cubic inch Chevrolet block, a couple of different versions, 330 hp or about 370 hp. The 350 magnum 300 hp is a good engine but sounds like it may not be the original engine. Doesn’t matter, Mercruiser engines are probably a lot easier for any accessory parts and service in Sweden anyway. 🙂 With the bigger 330-370hp engines, I think they did around 60 mph when new. Speed will be less if the boat is heavy, full of fuel, a lot of gear and people on board or the bottom of the hull is not clean. With most boats that age, there’s also a risk the stringers and transom have water intrusion and the wood inside is waterlogged. That can add a lot of weight to a boat. Did anyone survey or inspect the boat when you were buying it? The aluminum prop won’t help, not sure what size you’d need but a good stainless steel prop will be faster. Driving the boat takes time to learn how to get the best performance. Accelerate gradually with trim tabs down (if you have them) and the sterndrive down (in). Once up and running at 25 knots, you should raise the trim tabs all the way up and trim the sterndrive up a little to lift the boat up and reduce the amount of hull touching the water. Check on the trim gauge while the boat is out of the water, look where the gauge reads when the drive is vertical, that’s a good place to start once you’re up on the plane. You can gradually trim the drive up a little bit more but the aluminium prop will cavitate (slip) pretty easily. A stainless prop will bite and hold on much better. It’s a lot of learning, just go slowly and enjoy yourself. If the boat feels unstable, starts to bounce or react strangely, you’re pushing too hard. Try a Google search for Black Widow 24 speed and you’ll find info on other forums. I’m sure someone else will jump in here too, when they wake up. Most of our oso members are based in America. 🙂 Sorry it’s not as fast as your son hopes but it should be a bit quicker than 35 knots of the engine is running well, it’s not too heavy and you get a better prop. Meantime, remind him that although his mate’s boat is faster, a Donzi is probably a lot cooler. 😎 Good luck, RR |
Please post a couple of pictures of this boat, and a picture of the engine. That might be helpful in getting some additional answers to your questions.
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Originally Posted by 350scarab
(Post 4870937)
Please post a couple of pictures of this boat, and a picture of the engine. That might be helpful in getting some additional answers to your questions.
Thanks! RPM is 5200 on max throttle. No great difference in speed between 4000 and 5200. One of the ”things” that I hold my hand on is much cooler then the other. ps. I have problem uploading images. It says I’m not allowed to have url’s in my post…? |
Originally Posted by FreddeTrump
(Post 4871100)
Thanks! RPM is 5200 on max throttle. No great difference in speed between 4000 and 5200. One of the ”things” that I hold my hand on is much cooler then the other.
ps. I have problem uploading images. It says I’m not allowed to have url’s in my post…? |
Originally Posted by FreddeTrump
(Post 4871102)
”You are not allowed to post URLs until you have at least 10 posts” - I can’t show you guys the pics..
Just spam a couple of dead threads with posts until you reach ten. Or this thread, for that matter. You're not far from ten now. Easy peasy. Thanks. Brad. |
Originally Posted by Brad Christy
(Post 4871119)
Fredde,
Just spam a couple of dead threads with posts until you reach ten. Or this thread, for that matter. You're not far from ten now. Easy peasy. Thanks. Brad. |
Originally Posted by FreddeTrump
(Post 4871141)
Thanks Brad!
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Originally Posted by FreddeTrump
(Post 4871143)
Dummy message 1
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Originally Posted by FreddeTrump
(Post 4871144)
Dummy message 2
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Originally Posted by FreddeTrump
(Post 4871145)
Dummy 3
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Dummy 5
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Dummy 6
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That “thing” you’re touching is the exhaust riser. All your exhaust and cooling water goes through there and out the back. My boats, one side is always a bit hotter than the other, I think it’s just because of the direction the cooling water flows, getting warmer along the way.
The hotter one gets pretty warm, you should be able to touch it but don’t leave your hand on there too long! Those risers should be removed and checked for internal corrosion every couple of years, they don’t last forever. Nice boat, it looks like you’re having fun, regardless of how fast you’re traveling. :) RR |
Originally Posted by rak rua
(Post 4871182)
That “thing” you’re touching is the exhaust riser. All your exhaust and cooling water goes through there and out the back. My boats, one side is always a bit hotter than the other, I think it’s just because of the direction the cooling water flows, getting warmer along the way.
The hotter one gets pretty warm, you should be able to touch it but don’t leave your hand on there too long! Those risers should be removed and checked for internal corrosion every couple of years, they don’t last forever. Nice boat, it looks like you’re having fun, regardless of how fast you’re traveling. :) RR |
Freddie - by the looks of your pic, it looks like the boat is plenty fast!
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Originally Posted by liquidlounge
(Post 4871443)
Freddie - by the looks of your pic, it looks like the boat is plenty fast!
|
Well first thing i would do is a basic tune up....since its fuel injected i would top off with some hi-octane fuel and put some injector cleaner in the tank. Change the plugs/wires and cap/rotor. And finally that air filter looks caked up so take that thing off and clean it good to make sure its getting good air into the motor. If those basic things dont wake it up then i would start doing a compression test on the cylinders to see how far apart they are from each other......im sure its something simple if it runs good now...just need to "unblock" what ever is holding it back :)
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You are saying that there is "No great difference in speed between 4000 and 5200"
Are the extra RPMs from 4000 gained by trimming the drive, or also advancing the throttle? |
Originally Posted by Phazar454Mag
(Post 4872033)
You are saying that there is "No great difference in speed between 4000 and 5200"
Are the extra RPMs from 4000 gained by trimming the drive, or also advancing the throttle? |
Originally Posted by FreddeTrump
(Post 4872034)
Thank you for answering. The 1000rpm is made from advancing the throttle
What is the pitch of the propeller? Did you find out if it is an Alpha or Bravo drive and what the gear ratio is? |
I mean , it isn't exactly a racing boat that you've got there but are you sure that nothing much happens in terms of speed over the last 1000 rpm of the throttle range ?
As has been mentioned above , are you using the power trim properly ? You said that it's got an aluminium prop , they're not the best for all round top performance either . If it was as simple as 'changing a part' I'll make a recommendation assuming that your engine is in good shape and tune .. bolt on a super charger ! A 5.7 engine in that boat isn't much. You really need a big block that can put at least 400hp in the water at the prop to make that thing come alive. |
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