SIB not planing

[rivrunner]

Hi beamishken....tried in all 3 holes same result....perhaps hull and inflatable floorboard not inflated to max. it def. is a short shaft as transom is for short shaft.

[rivrunner]

fenlander....agree .....hard hull will def. perform better but with 380 lbs. on board i think i should be able to plane even with an inflatable hull floor board...no? .....just something not right when i engage the throttle and the engine pulls down the transom to the point where a bit of water comes over the transom.

[willk]

Originally Posted by Mikefule

JUST a thought - and don't ask me how I know this, I just do, right? - if you have transom wheels, they don't half make it difficult to plane if you forget to raise them.

My though as well

That said - I don't think an 8hp has a much hope of planing this load.

My tuppence is:

• Make sure the wheels are up
• Check the inflation of all sections with a gauge
• Trim the engine to lowest position but one
• Use a tiller extension
• Sit well forward while solo
• Keep all kit well forward
• Test
• Report back

[Fenlander]

>>> engine pulls down the transom to the point where a bit of water comes over the transom...

Yes that seems a bit excessive.

So to get a start point adding all the advice together. Outboard trim pin one of the positions from near the transom to the mid one. Tubes and floor 100% to pressure... rechecked when its been on the water a few mins. Two folks maximum with you at tiller and other in/near bow.

See what that does then work from there with the third person.

[Mikefule]

Good advice. First, see if the engine will plane the boat with only 1 person in it. If you have checked everything (tubes, floor, keel) and the boat won't plane with only 1 person, it points to a different problem such as the engine losing power, or the gear box slipping, or the prop being in appropriate or damaged, or something sinister like that.

If it does plane with 1 person, try it with 2.

If it planes with 2, try it with 3.

If it planes with 2 but not 3, then it is the wrong combination of boat, engine and crew.

Good luck.

Incidentally - there is more to SIBbing than just planing. You can have a lot fun chugging around and exploring.

[rivrunner]

mike, fenlander and willk....thks for the advice. I will def try all these next time out. If same result ....will hydrofoils work?.....stingray xpi?

[Mikefule]

Originally Posted by rivrunner

mike, fenlander and willk....thks for the advice. I will def try all these next time out. If same result ....will hydrofoils work?.....stingray xpi?

Rather than gimmicks and gizmos, you'd probably need a bigger boat and or a bigger engine. (Or a lighter crew.)

[rivrunner]

If 8 hp 4 stroke mercury with 10 hrs on it can't plane a 73 lb inflatable with 380 lbs on board i'll be shocked1

[jeffstevens763@g]

i agree with Max you need more horses 8 is very borderline and no reserve power

[Last Tango]

How about a photo of your transom/engine.......you've not put a 21" shaft on a 15" transom....

[beamishken]

That boat will definitely plane with an 8hp we can get a 9ft to plane with a 5hp 1 up ! pump it up take all the excess kit and passengers out and give it a run to prove the engine, then start adding the junk back. If it won't plane light properly inflated then there's either something wrong with the engine or the prop

[rivrunner]

Hi beamishken....I agree... it should def. plane with 8 hp. 73. lb sib and 400 lb's or less total weight onboard. Manufacturer claims it can plane with 1 on 4 hp. i hope to test again this wknd....this time i'll make sure hull and floor mat are totally inflated...... i starting to really believe that the reason the engine was pulling down the transom when i throttled up was because hull and floor were not totally inflated......we'll see if we are right......engine sounds fine and has maybe 15 hrs on it....

[Mikefule]

Just to illustrate how much difference the trim pin can make:

The other day I was out on the river with my 9.9 hp engine. It comfortably got me on the plane, but at certain speeds it was splashing quite a lot of water up.

Yesterday, as an experiment, I moved the trim pin 1 notch, from 1 (lowest) to 2. With this adjustment, the boat wouldn't get on the plane and it sounded like the propellor was "skidding" - presumably sucking in air. I moved the pin back to 1 and it was fine again.

That is, 1 notch difference on the trim pin made the difference between comfortably planing and not getting anywhere near planing.

[Poly]

Originally Posted by rivrunner

.i don't think weight was a factor.....

it is.

[rivrunner]

weel beam...i took it out again and it didn't plane with 1....had 2 in and had no power. someone had a 10 ft inflatable also and he was flying around with a 9.9....he told me I should be doing the same and said i need to inflate it to the max and also told me my props might not be the right ones......any ideas?

[Fenlander]

A video would be a great help to us giving advice so we can see what's happening.

[rivrunner]

Hi Fen....wish i had one but i don't. when i throttle up ...i don't get any umph...guy told me thr props might not be right. i have had trouble planing and going up river against 3-4 mph current is very difficult..tried the trim in many positions and it's the same.

[Fenlander]

It's frustrating trying to help at such a distance when it still doesn't go right.

There are many of us on here who could take that outfit for a quick run and tell immediately if it was boat, engine or some other problem.

I think you need to find someone local to you who could do that.

[rivrunner]

I agree fen....and thks for ur help.....it frustrates me too when i see someone in an equilivant boat zooming around while i struggle against a 4 mph current.

[Mikefule]

Just a thought - and some of the more experienced here may say I'm talking nonsense. It seems unlikely that an engine would have such an inappropriate prop that the symptoms were as bad as described: not planing with only 1 on board, and struggling against a 3-4 kt current. An 8 hp engine is not a very specialised engine and is likely to come with a generally suitable prop - unless it has previously been fitted to something completely different like a 20 ft river cruiser.

Therefore, is it possible that the prop is slipping on the shaft? Many engines have a sheer pin which can snap to protect the gear box if the prop hits an obstacle. This is something I have never had to deal with personally, so it is wild speculation and I invite correction.