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Old 13-04-2015, 09:18 PM   #1
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Join Date: Dec 2014
Posts: 11
Prop query Mercury 150 4 stroke

Hi guys, wondering if anyone could offer any suggestions re correctly propping our new outboard?

Weve just re-engined our 6.5m Coded RIB (Ocean) from a 150 Optimax to the new gen Mercury 4 stroke 150....

Firdt run out today and very pleased generally.... Couple of differences i'd like to address though /if anyone can help with suggestions before we start experimenting......

The new unit is 8kg heavier than the old unit (ish) but despite this is sitting the sponsons lower (in water at rest where they weren't previously) as IMO the weight is set slightly further back on the new engine....

Upshot is the sponsons are sitting deeper when planing....i'd like to lift the hulls planing pad higher...with propping if poss....

The boat is used for a variety of uses and we propped according to need on the Optimax..... a 15 pitch 4 blade for heavy work (loaded up with water samples etc) and a 19 pitch laser 3 for the rest.....

Tried the laser 3 today and was surprised that the boat has the potential to rev out too much (past 6k rpm i reckon)....

Anyone have any suggestions what prop i might try to reign the revs in and give lift at the arse end?

Thanks in anticipation :thumbs up:

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Old 13-04-2015, 11:09 PM   #2
Frenchbruno's Avatar
Country: FRANCE
Interests: speed on water/technics
Boat make: INVADER
Engines: MERC 250XS/SM 1.62
Cruising area: south Britany

Join Date: May 2007
Posts: 526
prop choice

Hi, you're speaking about the mercury 150EFI 3.0liter isn't?
can you tell me what's your rpm with the laser 19 on the 150 opti at top speed light load.
Can you tell me what's the four blades prop reference for heavy duty services and rpm you reached with the opti when loaded?
After this I can suggest you some pitch choices if you want to use the same propeller style.
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