Help with Honwave

[dave gregson]

Hi,
Having recently bought a 2nd hand Honwave 3.5 with an 8 month old Honda 20hp I was eager to get out and give her a blast.
We launched in the Menai Straights, had a play around to get used to the boat and then ventured out in to the bay.
All was well and we had a great day until we started our cruise back.
When travelling back up the straights we started to encounter a few problems.
The engine started to struggle to get the boat on the plane. It started to what I can only describe as oscillating ( I think this is what it was doing similar to what my jet ski used to do?) Like a car wheels spinning!
There also appeared to be a fair amount of water in the boat but when we recovered it there wasn't too much??
We where travelling against the considerable tide run of the straights but the boat had performed really well at the mouth of the straights where the tidal rush is at its strongest?
We did manage to get her on the plane a few times but only at a slow speed and it would then start slipping again and drop off?
Hope this makes sense??
Thanks Dave

[dave3235]

Hi Dave

Was your boat correctly inflated .25 for the tubes and .35 bar for the keel topped up after you put your boat in.

[Fenlander]

Do you mean it was like this the whole trip but the return conditions showed it up... or did it struggle to plane the whole trip?

How many folks (heavy or light) and what amount of kit is important to know. Then you have to consider boat or engine problems.

As dave3235 says lack of pressure is the possible boat cause... particularly if the sausage keel had gone soft.

Re engine a 20hp should give good performance with that SIB assuming your load was reasonable. You would not expect running or reliability issues with an 8mth old Honda. A failing prop hub where the motor was powering but prop slipping could be the cause on an older motor but so unlikely on yours.

Do you have a Tinytach type device to know the revs and a GPS to know at what speed this problem was happening? Do you know your prop pitch? If it was too large and the engine struggling to drive it you could get this sort of problem... and if it were massively under pitched you could be bouncing off the rev limiter (assuming the Hondas have one).

[Poly]

Originally Posted by Fenlander

A failing prop hub where the motor was powering but prop slipping could be the cause on an older motor but so unlikely on yours.

A slipping prop can happen at any time if its encountered a solid object or rope like a lobster pot. I agree though that that wouldn't be my first thought.

Was it struggling/labouring like a car in too high a gear on a steep hill then "racing" when it got enough oomph or was the engine spinning away happily but the boat speed not corresponding?

[knube1]

If the trim on my 3.8 honwave with the BF20D is not set correctly I get prop slip as it planes.

[Poly]

Originally Posted by knube1

If the trim on my 3.8 honwave with the BF20D is not set correctly I get prop slip as it planes.

Oh that reminds me I have experienced an issue where the boat seems to surge (slip-grip-slip-grip) and fail to get on the plane if I have left it in shallow drive mode coming off a beach (essentially massively trimmed up). Its the sort of thing you can easily do with a small engine on remotes and is disconcerting until you realise what causes it. Not sure how likely it would be on a tiller.

[knube1]

Also experiment with the trim pin if not set correctly for the load in the SIB the prop can become aerated giving the feeling of slip.

[dave gregson]

Hi guys,

Thanks for all your responses.

We were out for approximately 6 hours fishing in different spots. The boat performed well until the final journey home?
I will check the pressure levels as this had crossed my mind but again it was fine for most of the trip.
I'm not sure what the prop pitch and do not have a rev counter. I had no problem at all getting it on the plane until the journey home?
There was only 2 of us in the rib with a bit of fishing tackle so weight shouldn't be an issue.
I had the trim set on the last but 1 setting? I will have a play around with this and see what it makes the difference?
The rib has a non return valve with a push in bung on the inside and a screw type attachment on the outside but with no bung? Is this correct and if so do you travel with the push in bung in or out? Forgive my ignorance but if it is a non return valve why do you need a bung??

Thanks for all your help

Dave

[sonicoid]

Regarding the bung, it's designed to drain water when on the plane. The bung is to ensure water doesn't leak back in when you are moving slow or are stopped in the water. So mine stays in unless I have water in the boat and I'm on the plane.
I experience the same issue with the same boat and engine at times.
I find the prop suffers from cavitation. Reasons are incorrect weight distribution, sea state and pressure in air floor. The temp of the water can really affect the air pressure. So its always best to pump the last bit of air when the boat has been in the water for a few mins if possible.
I'm sure that you don't have any issue with the equipment. Just a little trial and error required.

[jeffstevens763@g]

A soft keel will allow air to get trapped then it releases causing surging as the prop slips. Check the keel for leaks and the valve for dirt causing it To go soft over 6 hours

[Fenlander]

>>>I find the prop suffers from cavitation. Reasons are incorrect weight distribution, sea state and pressure in air floor.

Yes quite common in most air floor SIBs but much less so in an alloy floor model like the OPs.

Dave if it was fine all day until the return home then something changed... and keel pressure is the most likely factor. For next time out I'd get a small £10 tach so you can be sure what the revs are doing.

[dave gregson]

Thanks for all the replies guys!
Lots of ideas to try this weekend particularly with the air pressure.

cheers

dave