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Old 25 February 2012, 16:25   #1
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Country: South Africa
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6m rib merc 225hp plane out problems

hi i am new to this site

i have a 6m mono hull with a 225hp mercury blackmax

the problem is the bow is hi up in the sky and wont plane out

if i go full throttle feels like the boat wants to come right over

if i trim up boat doesn't move and revs up

if i play with throttle move to full then back half way boat moves slowly but then in any case bow goes hi in the sky feels like we gonna tip over

we where 2 in the boat mate was in front of centre console

gas tank in centre console

so what do u guys reckon, whale tale? sand bags in front

current prop size i think is 48-21p
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Old 25 February 2012, 16:42   #2
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225hp on a 6m rib??????????

i think that is your problem right there.

any pics of the rig?

cheers
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Old 25 February 2012, 16:43   #3
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yes i got some will post it right now
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Old 25 February 2012, 17:01   #4
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its not done as yet jst got the motor running so took her for a test,,,

still have to finish the stainless steel work and seating


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Old 25 February 2012, 17:05   #5
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Tail heavy and overpowered IMHO
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Old 25 February 2012, 17:08   #6
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so my there is no way my outboard can work?
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Old 25 February 2012, 17:08   #7
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that is not overpowered-that is WAAAAAY overpowered.

that is an accident wating to happen. sell the engine and buy something else is the way to fix your problem. something about half that size would probably be closer to the mark.

check the transom-it should give you a size/weight of a suitable engine.

i would be amazed if that engine lasted on the transom long due to the weight.

cheers
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Old 25 February 2012, 17:16   #8
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thks i jst had the rib made and i was gonna power it with a 60 yamaha which i had

but then the shaft was to short and the only think i could get my hands on with this mercury at the time and the people from boat shop said motor wont be to heavy

now i am stuck with this issue,
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Old 25 February 2012, 17:38   #9
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the people from the shop said that motor was ok?

what size exactly is the boat? it looks like about 5-5.5m which means a 75-115hp is usually the max. 6m boats generally are 150hp for reference as a guide.

that my friend is dangerous-take it back and see what they say.

there should be a makers plate on the transom-what size engine is on there?

cheers
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Old 25 February 2012, 17:44   #10
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Quote:
Originally Posted by Xk59D View Post
the people from the shop said that motor was ok?

what size exactly is the boat? it looks like about 5-5.5m which means a 75-115hp is usually the max. 6m boats generally are 150hp for reference as a guide.

that my friend is dangerous-take it back and see what they say.

there should be a makers plate on the transom-what size engine is on there?

cheers
thanks a lot it is exactly a 5.5m boat there is no plate on the hull what so ever

thanks, now we no bigger is not always better
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Old 25 February 2012, 17:57   #11
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5.5m your looking at about a 100hp typically is the max. there is also a weight limit you need to consider.

PLEASE do not use that boat with that engine again for your own safety.

do you have any pics of the transom from the inside? or who makes the boat?

cheers
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Old 25 February 2012, 18:14   #12
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lol i wont use the boat again!!! ill post some pics up of transom it looks pretty strong and thick fiber glass to me, i think it is a gemini not 100%, i am having endless problems with this boat it is brand new, first my motors shaft was to short, then i bought this merc which to find out had over heated so i opted to re do motor, only to find out no parts available in south africa. luckily my sister lives in miami so she fed ex all parts needed. eventually got motor running after 2 months then this morning when i wanted to test, cars drive shaft broke not of towing but jst of wear and tear. got tht sorted and then boat was driving 90 degree up in the air lol. and now its to powerful..........
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Old 26 February 2012, 03:11   #13
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So, new car, 7.5 metre hull and you're sorted - no problem
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Old 26 February 2012, 03:31   #14
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Engine is too big and transom may not be man enough to support it but rigged correctly and at the right height is should still work shouldn't it?

We were discussing overpowered tenders on ybw a while back where people are sticking massive engines on tiny tenders, even going for a twin set up on a 2.4m sib, I never tried it but it looked fun.

Massively overpowered dinghies, again - Yachting and Boating World Forums
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Old 26 February 2012, 04:59   #15
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thks but those mostly under 3m tenders ill sot some pics up of transom ect
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Old 26 February 2012, 05:18   #16
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Old 26 February 2012, 15:20   #17
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I have a 5.6m with a 200hp. It planes almost instantly even with a 25 pitch prop.

My boat was built as a commercial dive boat to carry heavy loads and that is why it was plated for such a large engine.

With the Suzuki I have, 150, 200 and 225hp all weigh about the same and you only use as much throttle or hp as you want. The way I see it having a 200 instead of a 150 is not any more dangerous if I don't use the extra power. Having said that I have major chine walk issues that I have yet to sort out.

With your boat, I would be checking engine height. With the motor trimmed so the prop shaft is on the same plane as the bottom of the boat, the cavitation plate should be somewhere close to the bottom of the transom or a touch above. Maybe post a photo if you are not sure.

Also make sure the motor is delivering full power. After a recent rebuild, it is certainly on the cards that seething may have been missed.

Try another prop, maybe the prop bush is letting go under load. A 21 prop should give you fantastic acceleration but not I'd the rubber bush starts sloping at the crucial moment.
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Old 26 February 2012, 15:26   #18
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thks so ill post a pic in the morn the motor revs up like a bomb, and it takes off very well too but like i say the nose doesn't wanna come down causing it not move
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Old 26 February 2012, 15:28   #19
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can u post a pic of your rig pls. kubcat
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Old 26 February 2012, 15:36   #20
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Pick up the engine two holes and see if you are different on the right track. Another solution is the flapper
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