New to me Livingston not performing at its best

[Horned Toad]

Just purchased 2012 12' Livingston (240 lbs) with 2011 Yamaha F15SMH (126 lbs) with 9.25 X11 -J1 prop. First outing with all gear and battery/fuel tank in stern and passenger mid., bow was high and could not get on plane. I figure total weight around 950 lbs. Moved batt. and fuel tank forward helped lower bow a bit but slow to plane. Installed Whaletail, much flatter out of hole and planes quickly. Still not getting RPM into the WOT range (5-6K). Getting to a max RPM around 4600. Boat had been sitting for 6-7 years in a garage unused. Rebuilt carburetor prior to use as engine would not idle.

Question is would a prop change help or should I look at a carb. re-jet or change out to a 20hp carb.?
Mike

 

[briangcc]

Going off what I'm finding elsewhere...max load (including people, gear, and motor) is 900lbs. So overloading it isn't helping anything. I'd confirm the total load and see if you can shed some excess weight.....

As for the motor, it looks like you'd need to drop the pitch some to get it into the WOT range. That might help with the planing.

As for the 20HP, again from what I'm finding thanks to Google, it would need remote controls - ie steering wheel and throttle on a side console. If you have that, it should be gtg for the swap. Just be mindfull that the 20HP may weigh more than your current 15HP so you need to take that into account with your max load.

 

[Horned Toad]

My numbers were including boat's weight. Could be weight, but I think I will try to decrease the prop pitch. Picking one up tomorrow. HP difference, from my research is jet size and maybe 3mm larger bore on carb. Was not talking about engine swap.
Thanks,
Mike

 

[Scott06]

My numbers were including boat's weight. Could be weight, but I think I will try to decrease the prop pitch. Picking one up tomorrow. HP difference, from my research is jet size and maybe 3mm larger bore on carb. Was not talking about engine swap.
Thanks,
Mike

You are low on rpm so need to go down in pitch like a 9" pitch should get you another 400 or so rpm which is still kind of low. If they make a 7" pitch do that as it should raise you 800 rpm vs the 11"

Yes it is common that manufactures use the same power head with smaller carb or restrictor plate and other changes to derate an engine. The old eveinrude/johnson 9.9 &15 hp engines are a similar example - difference was carb mainly. So if you can get 5 more hp with carb swap do it. It wont be a jet change likely the bigger bore carb for more airflow. Possible the carb has different jetting but that should come with carb

 

[Horned Toad]

You are low on rpm so need to go down in pitch like a 9" pitch should get you another 400 or so rpm which is still kind of low. If they make a 7" pitch do that as it should raise you 800 rpm vs the 11"

Yes it is common that manufactures use the same power head with smaller carb or restrictor plate and other changes to derate an engine. The old eveinrude/johnson 9.9 &15 hp engines are a similar example - difference was carb mainly. So if you can get 5 more hp with carb swap do it. It wont be a jet change likely the bigger bore carb for more airflow. Possible the carb has different jetting but that should come with carb

Thats what I have done, hope to try out the new prop this weekend. Still mulling the carb swap since it seems the intake is different also.

Thanks, Mike

 

[airshot]

You sure your motor is running up to par?? Had a 14' Starcraft with a 15 hp Evinrude that jumped up on plane easily, little slower with two guys and fishing gear but still got up. I would be sure your motor is running its best...try doing a compression test to check its health.

 

[Horned Toad]

You sure your motor is running up to par?? Had a 14' Starcraft with a 15 hp Evinrude that jumped up on plane easily, little slower with two guys and fishing gear but still got up. I would be sure your motor is running its best...try doing a compression test to check its health.

Yes, compression is good. Mine catamaran hull gets up slowly.

Mike

 

[Scott06]

Yes, compression is good. Mine catamaran hull gets up slowly.

Mike

Ok this is a power cat then ? You may check the motor height. My brother has a 17 ft Twin Vee Power cat w/ 60 hp yammaha- original dealer set motor way too low cav plate was buried

 

[airshot]

Yes, compression is good. Mine catamaran hull gets up slowly.

Mike

Ahhhh...didnt know it had a cat hull, those take extra power to get up and get going !!

 

[QBhoy]

Sell the 4 stroke and get a good late model 2 stroke. All will be well.

 

[Horned Toad]

Sell the 4 stroke and get a good late model 2 stroke. All will be well.

I like the 4 stroker. Problem solved. finally got a new 4 blade, 9.25 X 8 and RPMs are 5700 at WOT, motor sounds so much better. On plane within 8 seconds w/o the whaletail. Wife even commented the engine is much quieter. Thanks for the comments.

Mike