bbladesprops

Your slip is quite high with the 32 Bravo 1's. Over 18% with 1.5 g.r. You could gain substantially across the board with 5 blade propellers.

We have some 30 Maximus props available if you would like to try them.

We'll wait to see the pictures of the Bravo 1's if you can get some.

throttleup

A couple more questions;
Does the boat have a rooster tail when properly trimmed out?
How high do you have to trim to get max top end?
Does the bow seem to be too high, too low?
Even though you may not run your boat at WOT often it's important for the boat to be set up properly and you will find that performance will improve across the rpm range.

Matt

restabr

The boat has the normal Mercury mechanical indicators for drive trim - on those I ususal cruise with the drives trimmed out to only about three on the scale. That equates to just a little positive trim. Set up like that there is no rooster tail at all. At wot my mental picture of the wake is not quite as clear because I'm so focused on what's in front of me, but I would tell you that to get absolute max speed it have to be trimmed very far out - like 7 on the scale and that it does have a little rooster tail running like that. It also takes the boat forever to get up to that speed. It will get to approx 78 quickly, but every mph after that takes a while to build up. I would tell you that the bow seems low and that my understanding is that this is characteristic of 353's.

throttleup

I would consider spacers to lower the drives. If you have to trim the drives high to get max top end you probably have a rooster tail.

Based on your numbers from your Bravo 1's a spacer would be in order. 5 blade props may reduce the slip but with the added stern lift the slip may be just as high as it is with the 4 blade props. When slip is as high as yours is I would concentrate on getting the boat running properly before concentrating on your props.

This is assuming that your props are in good repair and they have not been "hacked" on by someone.

The spacers would address most of your concerns. Cruise speed should improve, top end may improve, the bow will be higher, which will allow you to run with less drive trim. The spacers should also address the planning issue you have; the props should not ventilate like they do now at 3000 rpm, also when you get the slip down and run a lower pitch prop the motors won't lug like they do when trying to get on plane.

We will have test spacers available next season so you can try a set of spacers and see how they perform on the boat, just like testing props.

Matt

restabr

Before I say anything else let me freely admit to not being the most techincal person in the world. Spacers will require longer drive shafts - correct? I'm assuming that your reasoning is that the more correct running angle and corresponding increase in efficency will more than over come the increased drag of lower drives?? Given that the boat is still exactly as it came from Formula I'm a little surprised that we would decide that Formula installed the drives to high.

Could ventilation lead to the discoloration on my prop - maybe sucking hot exhaust around the prop or something??

What's your guess at to the dollars to go with spacers and what length do you think is correct?

Again - Thanks
Reed

throttleup

Reed,

Boat manufacturers set the drive and due to many reasons they are frequently too high. There is a misconception in the boating industry that the higher the drive the faster you go. This is false.

Drive height is determined by hull design, drive design, power, prop, weight distribution and many other factors. If any one of these is changed it can require a drive height change.

The goal is to have the prop shaft traveling through the water parallel to the direction of water flow. All the thrust from the prop is being used to push the boat forward. Of course no two boats are alike and this can vary a little but as a general rule it works.

A drive spacer kit comes with a flat machined plate that mounts between the upper and lower drive units. It also includes proper length studs and a coupler to transfer the power from the upper vertical shaft to the lower vertical shaft. It's a fairly simple installation which requires draining the drive oil, dropping the lower unit, replacing the studs, put the spacer on the lower and then install the lower to the upper.

Cost of the spacers varies by manufacturer, about $400 to $1100. We will carry a line of spacers and will have spacers available for testing. We don't have pricing on the spacers we will carry yet.

I would start with a 1" spacer and see what the results are and then go from there.

Matt

bbladesprops

Reed

Since the late 1990's manufacturers have continued to raise their drives heights more and more. Fountain, although an awesome boat co., have been a leader in this trend. Heck, even Baja started to do this 3 years ago. Not really a good thing to do with those hulls. The theory is true, less drag you go faster. However, there is a point of diminishing returns and the efficiency actually goes in reverse. With a proper C.G. and a overall light wet weight, plus a boat that carries the bow well, higher "X" dimension's do reap big speed rewards.


Just to clarify, you don't need a longer drive shaft. The kit comes with a coupler that will mate or connect the upper and lower drive shafts.

I would still consider trying 5 blade propellers. Let us know if you're interested.

Spacers can be purchased in 1/2" increments. I believe IMCO has them starting for about $350.



One other thing

restabr

As promised here are pics of the blade in question - any thoughts are greatly appreciated.

Reed

restabr

Last One

throttleup

Has the burned blade ever been repaired in the past? Did it ever have a bend in it that was repaired?


Matt