Aerotec performance

[Kernow Buoy]

Aerotec 4.2 with a 30 hp Mariner, what sort of top speed should I be expecting, had it out twice and made sure floor pressure is good but am guestimating only about 18 knots, was expecting more?

[Max...]

You should get more than that for sure but guestimating speed is really impossible - check it with a GPS.

[Kernow Buoy]

there were two of us onboard and I'd be surprised if we were more than a couple of knots out, what's the consensus on predicted top end?

[paddlers]

I'd expect more speed. I get 18 in my Honwave 3.5 AE with a 20 hp Tohatsu 4 stroke with 5 of us in!

[Nick Hearne]

I can do 18 to 20 in my 3.8m with 15hp 2st with just me, I don't think you will see much over 20 with 2 up in yours! Not having a flat bottom like most sibs means it is not going to be as fast!

[C-NUMB]

Originally Posted by Kernow Buoy

Aerotec 4.2 with a 30 hp Mariner, what sort of top speed should I be expecting, had it out twice and made sure floor pressure is good but am guestimating only about 18 knots, was expecting more?

I had an Aeroteck 4.2 and a 25HP tohatsu, topped 26-27 knots when loaded very, very light and flat conditions. On the otherhand did a few longer trips with me and 2 teen girls + camping gear, then the speed was about 21 knots , not WOT but at maybe 90% throttle.

The 4.2 is pretty hard to get running fast as the shape of the V before transom is kind of wrong. I lifted the transom height about 40 mm as the 2ST Tohatsu L rig is longer than standard engines. It was surprisingly seaworthy but think the hull design works better in speed slower than 20 knots. What pitch prop do You have?

[Mollers]

Originally Posted by Kernow Buoy

Aerotec 4.2 with a 30 hp Mariner, what sort of top speed should I be expecting, had it out twice and made sure floor pressure is good but am guestimating only about 18 knots, was expecting more?

WTF have you bought now?!

You need help sunshine. Is there a self help group? Boatsandoutboardsanon?

"Hi, my name is Jeff and I cant stop buying........

[Kernow Buoy]

Originally Posted by Mollers

WTF have you bought now?!

You need help sunshine. Is there a self help group? Boatsandoutboardsanon?

"Hi, my name is Jeff and I cant stop buying........

Ah, enter the storm bringer
s'pose I was lucky to get this far without being rumbled, right, I had a genuine need for a good size quick launching quick Sib so there, simple.

I may however struggle to explain the the 'other' one

[Kernow Buoy]

Originally Posted by C-NUMB

I had an Aeroteck 4.2 and a 25HP tohatsu, topped 26-27 knots when loaded very, very light and flat conditions. On the otherhand did a few longer trips with me and 2 teen girls + camping gear, then the speed was about 21 knots , not WOT but at maybe 90% throttle.

The 4.2 is pretty hard to get running fast as the shape of the V before transom is kind of wrong. I lifted the transom height about 40 mm as the 2ST Tohatsu L rig is longer than standard engines. It was surprisingly seaworthy but think the hull design works better in speed slower than 20 knots. What pitch prop do You have?

Cheers guys, interesting, I was thinking mid 20's or so, prop wise I don't know the pitch, there's not a mark anywhere on the current one, on the top trim hole if I open the throttle it just rev's merrily away and spins without planing, third hole down it planes very quickly but wot looks to only about 4200-4400, engine height looks OK. If I was replacing the prop I'd be after something like a 13"?

[Mollers]

Originally Posted by Kernow Buoy

I may however struggle to explain the the 'other' one

Leave it to me.

[C-NUMB]

Tohatsu has a 1:92 gear ratio and think the standard prop was 11 pitch wheras the Rascall had 13. Tohatsu was better but had pretty high revs at WOT lightly loaded.
I did had ventilation issues unless boat was evenly loaded an airfloor pumped to absolutely max pressure. I think the pvc flor was slightly stretched on my boat, might be a part of the issue.

[Mollers]

Originally Posted by C-NUMB

..with me and 2 teen girls.

Oh my lord!! Don't tell him that!

"Honestly Fran, these Aerotecs won't run properly without them."