prop for better fuel consumption

[johndeerenut]

Re: prop for better fuel consumption

gotch i moved the motor a notch up but it just seemed to bounce up and down to much i dont have power trim so it seems to run best all the way down. i think the prop i have is a stock size and this boat when you crack down on it stands up and comes right out of the hole with no problems thats why i was thinking i could go up a size or 2. and i will post some pics in the starcraft section i love this old boat it is my catfishing caddilac!

 

[Silvertip]

Re: prop for better fuel consumption

I give up.

 

[ezmobee]

Re: prop for better fuel consumption

gotch i moved the motor a notch up but it just seemed to bounce up and down to much i dont have power trim so it seems to run best all the way down.

I think you're a little confused. We mean raise the motor on the transom.....as in actually remove the mounting nuts and raising the motor a hole or two. From your post I am gathering that you just tilted it and moved the tilt pin. But get a tach to make sure you're able to hit the recommended WOT RPM range.

 

[Bondo]

Re: prop for better fuel consumption

I give up.

Ayuh,.... I know the feeling,....

 

[johndeerenut]

Re: prop for better fuel consumption

oh i see what you are talking about yes sorry im new to boating this is my first boat so dont know alot about it so take it easy on me if it was an early 1930,s john deere i could tell you everything about it and build it from the ground up but im new to the boats i did notice that it seems the motor does set a little lower than most i have seen.

 

[ezmobee]

Re: prop for better fuel consumption

Pics would help. You want your cav plate about even to an inch above your keel.

 

[steelespike]

Re: prop for better fuel consumption

Don't look for a specific demension just raise it to a point just before venting(cavitation)becomes a problem.I probably mentioned careful prop selection can help gain the best height.

 

[johndeerenut]

Re: prop for better fuel consumption

another new guy question what is the cavatation plate and my motor is not new enough to have the tale tale for water. i have read a little on cavatation but never heard of the cavatation plate my prop size right now is a 13-1/4x17
and its a brp cause i put a new one on since i ruined my old one early in summer

 

[kenmyfam]

Re: prop for better fuel consumption

another new guy question what is the cavatation plate and my motor is not new enough to have the tale tale for water. i have read a little on cavatation but never heard of the cavatation plate my prop size right now is a 13-1/4x17
and its a brp cause i put a new one on since i ruined my old one early in summer

The cav plate is the flat plate above the prop.
Tell us more about how you trashed the other prop.

 

[steelespike]

Re: prop for better fuel consumption

Modern day reference is not "cavitation" plate but "antivent" plate.
Ventilation used to be called cavitation even in factory literature.
Cavitation is actually the boiling of water in the low pressure areas of a prop.
All props experience a certain amount of cavitation.Severe cavitation can cause premature damage to the prop.You don't feel cavitation you see its effects on the prop.
Ventilation is when a prop injests air causing it to lose its grip on the water.
Ventilation can be caused by too high of a motor position,to much trim out,
damaged or poorly designed prop,water disrupted water flow to the prop, weeds or trash in the water.
Pontoons are prone to venting because the water around the prop is so disturbed.
Your motor may not have a telltale but usually there is a relief hole that water come out of in some form.

 

[GeneH]

Re: prop for better fuel consumption

Get an accurate tach. The engine you have must be propped to run in the upper rated RPM range at full throttle. (Example: If the engine is rated at 5200-5800 RPM, you want to be close to the upper number at wide open throttle with normal load. If you are down around the lower number, the engine is working too hard) If you lug this engine, you will destroy it like putting a 4 bottom plow on a 630 John Deere and trying to plow in 5th gear. You cannot prop a boat without an accurate tach and overloading this engine will burn it up. My guess, and guessing is almost worthless without accurate information, is that you are propped about right. Do some internet searching on how to prop a boat. There is a ton of info up there. Good luck!

 

[johndeerenut]

Re: prop for better fuel consumption

i trashed my other prop by fishing an area on the ohio river that i have fished a hundred times before only this time it was 2 weeks after some good flooding and i guess where i was had silted in from the flood and when i went to leave i felt something and saw mud so shut the engine down and pulled my motor up and sure enough bent the blades. i went back to the doc dad bent it out but i got a new one the next day cause i didnt want to ruin my seals. i see what yo all are saying i know a 2 stroke has to be wound out and not lugged just the same as a diesel or it can cause damage.yeah i would like to see a 630 pull a 4 bottom in 5th you could get some plowing done for sure.