Few boat related issues...help please!

MystyBlue2

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hi folks i have a 12ft seahog tardis (dory style hull) and a 25hp mariner 2cyl 2 smoke. (1980 jap model)

I bought the boat in January this year and needed ALOT of TLC, however the prop that was on the motor was a SOLAS 9.9x10 and was in very bad condition. I looked online for an identical prop and was only in Australia and £130 to buy and £130 postage! Far too steap in my opinion for a prop for this motor so i scoured flebay and found a prop that fit my motor with the extra expense of a hub fitting kit. Problem is the only prop i could find to fit had a 12inch pitch and the one that was on when i bought it was 10inch pitch. But tbh the prop that was on might have been totally wrong to begin with as they where a penny short of a pound......Anyhow prop is on and the boat feels really sluggish, will only get on plane if i strip all gear out altogether and just have me, fuel and small tool kit onboard, any load what so ever even 1 medum build passenger and she will only reach 9kn MAX and drags its back end and this is at WOT. can anyone advise weather its worth trying to get a 10inch pitch prop? Would this improve matters or would there hardly be any differance to justify the cost?

Secondly after ive been at WOT for some time trying to reach fishing spots and im stopping the boat to fish im getting alot of bubbles bubbling from under the transom/chines, best way i can describe this is like the water under the transom is (boiling) lasts for 30 seconds or so then stops. Is this just air being trapped between bow and waterline and being pushed toward the stern or could this be something abit more sinister? Or maybe contributing to my lack of planing ability?

Sorry for all the blab folks and please be patient as i havnt been boating for decades so im still a noob haha.

Looking forward to your thoughts cheers
 
Mariner Prop Style Charts by Model | Solas Propellers

choose your spline. I've assumed

25HP Japan Yamaha Origin (10 Spline) 1980 - 1984

Mariner 25hp Propellers, Japan Yamaha Origin 10 Spline - prop charts


choose pitch etc -

9.910R3211-099-10

Google search 3211-099-10 UK shopping

plenty to choose from.

e.g. Osculati 52.405.02 - Propeller YAMAHA 9.9 x 10: Amazon.co.uk: Sports & Outdoors

I'd say you are pitched too high. Go back to 9.9x10.


Bubbling sound. Check foam filled cavities havent filled with water.
 
Ah awesome thank you very much for that info il take a look at those ones and its visible bubbles i can see bubbling up from under the boat past my transducer to the surface, its like there is a scuba diver directly under my hull and his bubbles are coming up at the stern/transom. Ive recently redone the soggy floor and removed all the soaked waterlogged foam, i removed the deck inspection hatch to see if bungs where allowing water in and its completly bone dry. The bubbles has me really stumped...
 
I would say that is most likely just air trapped beneath the chines / cathedral hull. It does seem unusual though.
 

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