New F470 owner, questions

[Dkillough]

Afternoon all,

Recently picked up a lightly used F470 with aluminum hard deck and a 40hp Merc.

I have a couple quick new guy questions, and the Zodiac manual wasn't super helpful.
Inflation: as I understand it, if I turn all the valves to the middle of the red, it inter-communicates and I can fill the side tubes from one valve. Is that correct? Does this also fill the speed tubes? I've read that you need to adjust pressure after sitting in the water, and you can't get to the speed tube valves once it's in

Secondly, what I can I expect as an average cruising speed with the 40 horse? Pretty light load, say 600lbs total people, fuel, gear, etc.

I mostly plan on using the boat for crabbing around the bay, and occasionally making a 7 mile run across a stretch of the Puget Sound to my folks' house. All protected water, I know the boat is plenty capable of handling that. I suspect the Missus will keep me honest about keeping it to fair weather only, she won't like taking spray.

[909]

They will never admit it

But deep down inside

All women love taking spray

[HurricaneTender]

Hi,
Here are a couple of answers. Hope this helps.

Inflation: as I understand it, if I turn all the valves to the middle of the red, it inter-communicates and I can fill the side tubes from one valve. Is that correct?
YES Does this also fill the speed tubes? YES. As long as the connection is made from the main tube to speed tubes

I've read that you need to adjust pressure after sitting in the water, and you can't get to the speed tube valves once it's in. Correct, the colder water temperature will reduce the pressure in the tube. No, the speed tubes should be connected to the main tube

Secondly, what I can I expect as an average cruising speed with the 40 horse? Pretty light load, say 600lbs total people, fuel, gear, etc.

About 15-18kts

[Locozodiac]

Yes, need to have that nice 470 Sib fully reinflated to their factory stated working pressure after the overall pressure that was inflated to settles down soon after sitting on water for some minutes rest specially if boating in cold water.

To take the max HP out of that motor need to install an induction type tach, go for a wot run as usually loaded and report achieved max wot rpm over flat non windy water conditions. Will know if the motor is revving inside its min-max wot rpm range factory stated. If under will be lugging the motor which is bad.

Propping the motor right to run towards its max wot rpm range will achieve a faster hole shot, carry more passengers, once there can throttle at the crusing speed you feel most comfy with at reduced thottle along much less fuel consumption. 1/2 to 3/4 throttle will be sufficient for a nice cruising speed at whatever speed a GPS indicates...

Happy Boating

[Dkillough]

Thanks for all the help. I've since learned that my particular boat does not have the main tubes connected to the speed tubes, I'll have to source some parts for that.

I took the boat for a spin and found that water gushes between the outboard and the transom. I'll throw a link at the bottom with some video and pictures. I've read that this means the motor is mounted too low. It's a 20 inch shaft, but I believe the early 470s had a low transom.

Based on the pictures below, is my engine in fact too low? The anticavitation plate is well below the transom, but about online with the bottom of the speed tubes. I can't move it up without building up or replacing the transom.

Photos here: https://photos.app.goo.gl/CjkXR3zVJmpK6ff47

[909]

1/8 inch per 1 inch of set back

or 1 inch per foot

Your stern is getting "buried" , all that water gushing in is no good.

[Locozodiac]

If water gushes/splashes between the lower leg and the transom the hardened water flow at speed is probably being smashed over the small upper water deflector plate. In reality needs to pass under the small plate where the sharp edge is located to make a clean water cut. Go for a wot run on flat water, pull your head side of motor and visually check if it's happening. If so raise the motor one notch al a time till that condition is fully canceled. Report your findings...

Happy Boating

[cgoing]

Originally Posted by Dkillough

Thanks for all the help. I've since learned that my particular boat does not have the main tubes connected to the speed tubes, I'll have to source some parts for that.

I took the boat for a spin and found that water gushes between the outboard and the transom. I'll throw a link at the bottom with some video and pictures. I've read that this means the motor is mounted too low. It's a 20 inch shaft, but I believe the early 470s had a low transom.

Based on the pictures below, is my engine in fact too low? The anticavitation plate is well below the transom, but about online with the bottom of the speed tubes. I can't move it up without building up or replacing the transom.

Photos here: https://photos.app.goo.gl/CjkXR3zVJmpK6ff47

470’s were built with 15,18, and 20” transom. Yours is a 15” model . A 20” will never work well on that boat.

[909]

Temp fix :

Raise the transom with sealed marine ply 4 layers sandwiched essentially "lifting" your prop / outboard to accommodate your outboard.

Use stainless hardware to secure , with silicone or epoxy to seal .