New Guy trying to go fast!!

[79Formula]

I recently purchased this 1979 Formula F18. It has a 24* deadrise and is 18ft long, has bennett trim tabs, and weighs 2600lbs. I replaced the transom and motor mounts. I also converted to center rise exhaust. I got her all back together and it ran as follows. With a no name 21p prop it ran 49-50 mph on gps at 5500rpm and the revs would have kept climbing if i let them. I tried it with a no name 23p prop that also had no cup. If anything the prop looked like it has negative cup. Anyways with the 23p I got 53mph at 5200rpm. trimming up raised rpm but not speed past that point. I know the prop choice is not ideal. I would like to put it in low to mid 60s. Where should I start and also what should I expect out of my hull?

 

[jestor68]

Re: New Guy trying to go fast!!

Not sure what a "no name" prop is. Assuming that your motor is of a similar ('79?)vintage, the max sustained operating rpm of the 260 is 4600 rpm.

If it's able to spin the non cupped "no name" prop to 5200 rpm, a quality SS 23" cupped prop will pull that rpm down several hundred rpm and gain several mph. A good prop should get to the high fifty's range, but I doubt that you will push that hull design to 60-ish without more horse power. Since your Alpha drive is limited to 300 hp, that is your real limiting factor.

I'd bet that '79 boat was designed(and powered) to do mid fiftys. Trying to make it go 60+ is going to get expensive, as in lots more power and an up graded Bravo drive. All this is doable if you're willing to spend the money to go a few MPH faster.

 

[79Formula]

Re: New Guy trying to go fast!!

The motor is in excellent condition. Sounds extremely healthy. It has an edelbrock carb and intake on it. I also updated from log to center rise manifolds. I feel as if the motor should be making at least its rated hp (260). From what I have read on other forums is the F18 hull chine walks real bad at 65. I also noticed that all the props I have are all dinged on the edges. I guess when you are talking about getting maximum performance, prop condition is crucial.

 

[jestor68]

Re: New Guy trying to go fast!!

From what I have read on other forums is the F18 hull chine walks real bad at 65.

That's because you're trying to push it past it's design speed. The F-18 is a runabout. It is not a go fast boat.

A quality SS prop will get you into the high fiftys. Trying to go further is going into dark territory; where bad things can and do happen.

 

[emoney]

Re: New Guy trying to go fast!!

I agree with the 2 above posters, trying to push that current set-up into the mid 60s may result in a "short-term" ride. There are tons of hulls out there built for speed, and then there are others built for family-style-boating. Yours seems to fall into the latter and forcing it into the former may result in some very bad memories. Kinda akin to taking a fully dressed bagger to the round track bike races. OH, you could probably work hard enough to get it to compete, but that first corner is probably going to be a doosy for you. Good luck and I hope you safely reach your goal (although, I hope it's in a different boat, lol).

 

[Bondo]

Re: New Guy trying to go fast!!

The motor is in excellent condition. Sounds extremely healthy. It has an edelbrock carb and intake on it. I also updated from log to center rise manifolds. I feel as if the motor should be making at least its rated hp (260). From what I have read on other forums is the F18 hull chine walks real bad at 65. I also noticed that all the props I have are all dinged on the edges. I guess when you are talking about getting maximum performance, prop condition is crucial.

Ayuh,.... Right up there with Road Racin' on flat tires...

 

[Bamaman1]

Re: New Guy trying to go fast!!

I had a boat of another brand that looked like this one. It would chine walk @ 47 mph and higher. Every boat has its limitations, and you've just about hit it with your full hulled V-hull boat.

My best suggestion is to go to a prop shop and talk to the owner about what would be your optimum propeller. His expertise is free--especially if you buy from him. You might get a couple of mph--but not into the mid 60's.

You'd need to be running a lower profile boat--like an old Checkmate or Baha--to get into the 60's. But they ride like rocks.

 

[79Formula]

Re: New Guy trying to go fast!!

Do boats gradually become unstable or is it quick like hi-siding a motorcycle? At wot in the low fifties it feels like the boat is deep in the water still. I feel like there is alot of speed to be had IF I can free it up.

 

[Frank Acampora]

Re: New Guy trying to go fast!!

The boats I had that chine walked would start at a given speed then go into a feedback: if I did not back off it got worse. I never had the guts to see if it would disappear at higher speeds.

With a deep vee hull, the general consensus is that as speed rises, the hull lifts and at one point there is not enough hull in the water to support it. It falls off to one side (on the chine) then rises and flops over to the other.

 

[tpenfield]

Re: New Guy trying to go fast!!

Get a Formula 292 instead . . . probably will do 70 mph.

Prop selection is not going to get you to 60 mph, sorry to say.

 

[79Formula]

Re: New Guy trying to go fast!!

I would go bigger if I could afford it. The little boat fits in my garage and uses little fuel. I would love a twin engined formula. There is a guy on offshore only that had his F18 going 65 with a close to stock 350.

 

[jestor68]

Re: New Guy trying to go fast!!

This and a good 26" pitch prop should get you going.

 

[Bondo]

Re: New Guy trying to go fast!!

View attachment 171370 This and a good 26" pitch prop should get you going.

Ayuh,.... for a few seconds anyways....

 

[steelespike]

Re: New Guy trying to go fast!!

Your trim tabs are very helpfull getting on plane and improve ride/handling but the fastest setting is usually all the way released.
Look up bass boat crash on you tube. You'll see the kind of thing that can happen even though sober and apparently not at full speed.