Reply
 
Thread Tools Search this Thread
 
Old 23 May 2018, 14:55   #1
Member
 
Country: UK - England
Town: SIDMOUTH
Boat name: Honwave
Make: Honda
Length: 3m +
Engine: Honda 2 Stroke 20hp
Join Date: May 2018
Posts: 18
Sib with 20hp

Hi all I have bought a second hand sib with a Honda 20hp outboard, it starts without problem every time but when Iím on full throttle it sounds like itís been knocked into neutral and revs high, as soon as I ease of the gas it recovers and is fine but I canít run at full speed as it keeps doing this .....any ideas ?? Thanks
__________________

__________________
CHRIBS is offline   Reply With Quote
Old 23 May 2018, 15:08   #2
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Mariner 9.9 2018
Join Date: Nov 2007
Posts: 4,206
Which Honwave did you get?

BTW no need to ask the same question in two places as it confuses which thread to answer.
__________________

__________________
Fenlander is offline   Reply With Quote
Old 23 May 2018, 15:16   #3
Member
 
Country: UK - England
Town: SIDMOUTH
Boat name: Honwave
Make: Honda
Length: 3m +
Engine: Honda 2 Stroke 20hp
Join Date: May 2018
Posts: 18
Oh I’m sorry I’m new so forgive me...it’s a 3.5m with 20hp Honda
__________________
CHRIBS is offline   Reply With Quote
Old 23 May 2018, 15:19   #4
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Mariner 9.9 2018
Join Date: Nov 2007
Posts: 4,206
Hey it's fine... no way of saying without it sounding like a grumble but it does help if all replies are together. In the other thread Poly has wondered about a slipping prop hub. Another possibility is it is an effect you can get with SIBs if they are underinflated particularly the keel (I assume you have the alloy floor model with sausage keel under?).

Even when everything is spot on certain OB and SIB combos with certain loading balances in certain sea states can do this due to the prop losing its grip.

This happens with SIBs due to the flexible nature of the hull.
__________________
Fenlander is offline   Reply With Quote
Old 23 May 2018, 15:28   #5
Member
 
Country: UK - England
Town: SIDMOUTH
Boat name: Honwave
Make: Honda
Length: 3m +
Engine: Honda 2 Stroke 20hp
Join Date: May 2018
Posts: 18
That’s really kind I will check all the pressures and see if this helps I will also get the prop slip checked ...they both sound sound advice and thanks so much
__________________
CHRIBS is offline   Reply With Quote
Old 23 May 2018, 20:03   #6
Member
 
Lee1's Avatar
 
Country: UK - England
Town: South East
Make: Waveline V SIB
Length: under 3m
Engine: Mercury 25hp
Join Date: Sep 2017
Posts: 384
Sib with 20hp

Your cavatating, try moving your position in the boat to balance the weight, as above if it's a V floor this is one draw back of the v floors
__________________
Lee1 is offline   Reply With Quote
Old 23 May 2018, 23:59   #7
Member
 
Country: UK - England
Town: Lincolnshire
Boat name: Mousetrap
Make: Zodiac Cadet 310S
Length: 3m +
Engine: Mariner 4 stroke 9.9
Join Date: Sep 2014
Posts: 297
Based on the limited information, my first thought is that once the engine reaches a critical speed, the prop is sucking in air, meeting less resistance, and therefore allowing the engine to spin faster. I had this on my 9.9 when I tried a different tilt setting as an experiment.

This sounds more likely than a mechanical problem with the engine.

Try the tilt one notch lower and if that doesn't work, try 1 notch higher.

It may also be the trim of the boat. Where you sit, and where you put any heavy kit can affect the trim, raising or lowering the transom by an inch or two.
__________________
My novel, "Bridge of Otherwhere" 2018 by Michael Wilkinson, now available for download on Kindle.TinyURL.com/Bridge-of-Otherwhere
Mikefule is offline   Reply With Quote
Old 24 May 2018, 03:38   #8
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Mariner 9.9 2018
Join Date: Nov 2007
Posts: 4,206
>>>Your cavatating, try moving your position in the boat to balance the weight...


Cavitation is often spoken of in these situations but it's not the correct term... no big deal though as we all know what someone is trying to describe. Cavitation is a sort of boiling of the water adj the blade surfaces usually due to prop damage or the wrong prop for the boat. It can be felt as a vibration and can eat the paint and prop surface away with pitting.

If it's not hub slip but the prop taking air as Mike describes it's called Ventilation. This can be due to the wrong OB height or trim and in hard boats set up correctly is only usually found on tight turns. But as I explained above the flexible nature of SIBs can (can, not will) trigger this far more easily if some set up factor is wrong... or just down to a particular type that is very prone.



>>>if it's a V floor this is one draw back of the v floors


No that's totally wrong... it has nothing to do with V floors.

The most prone SIB design to triggering ventilation is the flat air floor with a low pressure sausage keel. In certain makes/setups it's really hard to stop this happening.

Better but the next most prone are the shallow V air floors like Honwave (and your Waveline Lee). Usually but not always the longer the model the more likely the problem can be.

Less prone to ventilation is a well set up alloy floor SIB with low pressure sausage keel.... like the OPs... and that's why I think we can quite easily talk him through sorting it.

The SIB very least prone to ventilation is the Aerotec as it is a true V hull for its whole length which by its design doesn't trap dollops of air under the hull. In all Nm we have covered at sea in our Aerotecs ventilation and the associated prop slip has never been an issue.
__________________
Fenlander is offline   Reply With Quote
Old 24 May 2018, 13:34   #9
Member
 
Country: UK - England
Town: SIDMOUTH
Boat name: Honwave
Make: Honda
Length: 3m +
Engine: Honda 2 Stroke 20hp
Join Date: May 2018
Posts: 18
Hi thanks for This I have looked at the prop today and the castle nut was loose enough for me to turn with my hand ! I wonder how much to tighten and see if this helps as well as the other suggestions . I will also look at the outboard angle as it’s currently set on the pin nearest the boat
__________________
CHRIBS is offline   Reply With Quote
Old 24 May 2018, 14:35   #10
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Mariner 9.9 2018
Join Date: Nov 2007
Posts: 4,206
Obviously good to tighten the prop nut correctly... to lose the prop would be most unfortunate! But as it's on a spline it won't help the "spinning" effect.

Yep try all the things we've advised and I hope you can report a cure.
__________________

__________________
Fenlander is offline   Reply With Quote
Reply

Tags
sib

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 22:49.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.