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Old 10 July 2006, 12:31   #1
Country: UK - England
Length: no boat
Join Date: May 2006
Posts: 133
Trying to find rpm

Fairly new to ribbing but find this site extremely helpfull, fingers crossed someone can help with this one.
Since using my rib I,ve noticed that my honda 90 never gets above 5000k at full throttle(Honda state 5k-6k).I thought I would look under the bonnet and investigate.Noticed that the throttle linkage was only at the 3/4 position/usage also the carbs were not fully open.So I thought it was a simple task of adjusting the throttle cable.
Next trip out WOW 5800k rpm and a lot faster great I thought!
Not so, as I went into neutral the idle speed was 1200rpm and subsequently could not get it into gear.Back under the bonnet back to original everthing ok.
What am doing wrong?
Why cant I find that extra rpm?

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Old 10 July 2006, 12:35   #2
Andy Moore's Avatar
Country: UK - England
Town: Cowes, Isle of Wight
Boat name: Ditherer
Make: Avon Adventure 620
Length: 6m +
Engine: Optimax 135
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I am no expert, but what about a different prop?

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Old 10 July 2006, 12:54   #3
Country: UK - England
Town: I.O.W/Bristol
Boat name: HotShot
Make: shakey
Length: 5m +
Engine: 70hp Tohatsu
Join Date: Jul 2003
Posts: 1,543
if its anything like my tohatsu...

There will be an idle adjustment screw located by the carbs which adjusts the rpm at idle. It should be about 900 ish out of gear and 800 ish in gear i think. It sounds like you need to adjust the throttle cables as you did but then adjust the idle screw to calm her down.

Failing that, props wrong
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Old 10 July 2006, 13:23   #4
Country: UK - England
Town: Leatherhead
Length: no boat
Join Date: Aug 2001
Posts: 907
Originally Posted by Andy Moore
I am no expert, but what about a different prop?
Sound about right. When we changed the props over on our Suzuki the rpm went up by over 600rpm.
Peter (nick, nick) T

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Old 10 July 2006, 16:41   #5
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Country: UK - England
Town: The wilds of Wiltshire
Boat name: WhiteNoise/Dominator
Make: Ballistic 7.8/SR5.4
Length: 7m +
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MMSI: 235090687/235055163
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If the throttle isn't opening fully then that's where the problem lies- WOT means the butterflies at fully open position. I doubt it's a prop problem.

How does the linkake work between the cable end and the throttle butterflies? Could it be a slightly bent linkage bar or similar? I'm not familiar with the setup under the cowl on Hondas.
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Old 11 July 2006, 05:59   #6
Country: USA
Town: boston
Boat name: Miss bad 61
Make: Crapko, AKA Mako
Length: 5m +
Engine: OMC Mod50
Join Date: Apr 2006
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you needed to adjust the carb linkage, not the cable, put the cable back.
should be a cam that drives the carbs, depending on what flavor moda ya got.
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Old 11 July 2006, 07:23   #7
Country: UK - England
Town: Northampton/Devon
Boat name: Cormorant
Make: Southern Pacific
Length: 4m +
Engine: Mariner 40HP O/B
Join Date: Jun 2006
Posts: 5
Sorry to disagree but my first check would be to see the amount of movement on the throttle cable, it sounds as though you are not moving the linkage far enough, ie adjust for full throttle and the cable then does not retract far enough for tick-over.

If you check inside the gear/throttle lever on the console you should see several different positions for attaching the throttle cable, each giving a different amount of cable movement between tickover and full throttle. Just chose the one that suits the amount of movement that the engine needs.

Hope that this helps.

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