Can you experts help me please?

I've been boating with my family my whole life and have always loved it. We are buying a newer 26ft Crownline after a massive 3 month search.We have finally decided on a boat but during all my searching I have came up with quite a few questions and I was wondering if all you experts could help me out with my questions.
#1. I know that trim tabs create lift on the stern but how should they be used in cruising, skiing (mainly the whole shot), top speed, and how do they effect fuel economy. Any other basic and/or complex information would be awesome.
#2. What are the differences in the prop pitch? Such as the angle of blades and their performances? Which pitches are best for what activities?
#3. What are the ratios in the engine and their purpose? Such as the difference between a 2.0 and 2.43?
I'll probably have more to come don't worry. Thanks

Re: Can you experts help me please?

Welcome to Iboats!

Well, I'm no expert but you have a boat of similar size to mine so I can comment on your item #1 regarding cruising and some general use.

Yes, with a lot of weight in the stern, trim tabs in the down position can help the boat get up on plane.
Once on plane, you now have to balance the use of the trim tabs and the trim position of the drive based upon water conditions and weight/balance of the boat to obtain an ideal running position.

In my case, once up on plane, I put the trim tabs all the way back up then put the drive at a position of about 1/4 up based upon the trim position gauge on the dash.
How did I determine that? Trial and error finding that when up on plane and trimmed to 1/4 out, the rpm stay about the same but the mph goes up. Some might call this the "sweet spot".

That's my starting point.
Based upon the direction of the swell, how the weight of the boat is distributed (folks on board, etc.) I may need to put 1 tab down to create lift on one side of the boat which brings the opposite side of the bow down.

Change course, and the sea direction changes and you may need to adjust trim tab position again.

Practice and go from there.

FWIW: When creating a new post, you might want to make the title something specific on the intended concern to get the best visibility.

Mark

Re: Can you experts help me please?

1.... I dont have trim tabs but I think they dont lift stern. Add pressure/drag which pushes bow down. Assuming morr drag means burning more fuel.
2....prop pitch is like gear ratio of car. Lower gear more low end power. Higher pitch means more speed but it gets very technical.
3....simular to question 2

Re: Can you experts help me please?

#1 Trim Tabs - Yes they push the stern up, thus driving the bow down. Useful when trying to get up on plane fast or with lots of weight in the boat. Once the boat is on plane, raise them up to achieve greates speed and effieincy. Also can be used to keep the boat from "hopping" from wave to wave in rough water. (this use is usually used in offshore, rough water applications). If your running in rough water and you find your bow dancing up and down to the point of being uncomfortable or dangerous you can reduce speed obviously but also try giving a "little" down force to the bow. Start slow because you do run the risk of "planting" the bow and having a wave come over the nose of your boat. Additionally, if the boat is heavy on one side due to an ice chest or a "large" buddy, you can use one tab to level the boat.

#2 Prop pitch. Pitch referes to the distance a prop would theoretically travel in one revolution. So a 21 pitch prop would move 21 inches in one turn. However, this is not completely accurate do to prop slip but thats not important. What you need to know is that the higher numbers will give you a higher top end and less of a whole shot. But you must be careful not to "over prop" your engine. You want to find a Prop that allows the boat to run at or near manufactures designated highest RPM level at wide open throttle (WOT). It is not good for you engine to try and turn to much prop or to little which will let it run way to many RPMs. A good prop shop can usually get you dialed in if they know the specks on your boat and motor. Keep in mind that the diameter of the prop has something to say about all of this and the number of blades. Usually a good 3 blade prop fits most applications. Boats that need a really good whole shot such as shallow water boats usually run 4 blade prop for extra "bite" but sacrafice a few MPH on the top end.

#3 The engine ratios you mentioned are usually the gear ratios in motor (gear box) They are really irrelevant to most boaters because the difference can be made up in the Prop. High performance boaters are usually interested in this sort of thing but the average guy like you and I doesnt care as long as the final result is optimum RPM levels.

Hope this helps

Dave

Re: Can you experts help me please?

Mojo27 said:

What are the ratios in the engine and their purpose? Such as the difference between a 2.0 and 2.43?

Click to expand...

Slow Ride said:

The engine ratios you mentioned are usually the gear ratios in motor (gear box)

Click to expand...

To prevent confusing new boaters...I want to address this. There is NO such thing as engine gear ratios. An engine (for our discussion) does not have any drive gears in it. That is what transmissions are for; or in this case, outdrives. If the OP has an I/O (inboard engine/outboard drive) the only "gearing" that he can affect is that of the upper gearcase of the outdrive. Unless that has been changed by a previous owner, the gearing of the boat has been maximized for proper function under most running conditions at the factory when it was built. This is why prop selection is the only way to effectively change a boats running behavior, short of engine or drive replacement.