front of boat is plowing through the water

[2004hemi]

I searched for an answer but never found one. I have a 1648 alum. flat boat with a 40hp yamaha outboard. The boat plans off real quick and rides good up to about 3/4 throtle, but when I open it all the way I can trim till it blows out but the front just plows through the water and I can't get it up enough. But if I back it to 3/4 again the front raises up and goes fine. So what could the problem be?

 

[calwldlif]

Re: front of boat is plowing through the water

If properly weighted, ect<br />Props can lift the stern. <br />Cupping, rake in a prop will give <br />lift.

 

[studlymandingo]

Re: front of boat is plowing through the water

What is your weight distribution like? Do you have a lot of weight in the bow???

 

[2004hemi]

Re: front of boat is plowing through the water

I have a trolling motor in the front and a battery both are on the oppisite side of me and I also extended my deck with wood but it never add to much more weight to the front. I had another motor on this boat before but it never had power trim and it wasn't as fast as this one but it was the same size motor, and it never did it with that motor.

 

[LubeDude]

Re: front of boat is plowing through the water

Here is my take.<br /><br />Your boat is a flat bottom and maybe still be underpowered so when you trim a bit, it actually helps, but when you trim too much, the boat is flat enough that you dont get porposing, it just settles back down into the water and plows. Its falling off its fulcrum. Just trim it untill it starts to fall off, and then back it off a click or two and leave it there while WOT. Thats your sweet spot so to speek. A better prop with some cup may help you out some.

 

[2004hemi]

Re: front of boat is plowing through the water

Thanks for the help I think I will try a different prop and see what it does when I bought the motor which was just a few weeks ago they told me if I didn't liek the prop I could bring it back for another so I think that will be my next step

 

[Boatist]

Re: front of boat is plowing through the water

How far out have you trimed the motor? I do not like batteries up front or for that matter anything heavy. Batteries do not like the shock and vibration of the bow either. Trolling motor has to be up front.

 

[deejaycee_2000]

Re: front of boat is plowing through the water

set your trim, one clip higher or two, keep your fuel tank and battery right at the back ....

 

[2004hemi]

Re: front of boat is plowing through the water

I already have one battery in the back and two 6 gallon gas tanks so I do have more weight in the back thats why I didn't know what the problem was.

 

[Jdeagro]

Re: front of boat is plowing through the water

Do you have a hydrofoil on the motor?

 

[2004hemi]

Re: front of boat is plowing through the water

no I don't have a hydrofoil on it I was going to put one but when I tried the motor out it plans off real quick so I never got one.

 

[KCook]

Re: front of boat is plowing through the water

Try setting the motor mount at different heights (change the hole).<br /><br />Kelly Cook

 

[2004hemi]

Re: front of boat is plowing through the water

I have the motor on the highest hole it will go on, and at that level the plate is sitting where it should be

 

[KCook]

Re: front of boat is plowing through the water

Even so, I would drop it one hole and see what difference there is.<br /><br />Kelly

 

[nevd]

Re: front of boat is plowing through the water

What is the height of your AV plate (separate readings for both front and back) in relation to the water when you have the operating problem and what is your speed?

 

[2004hemi]

Re: front of boat is plowing through the water

I don't know my speed I dotn't have a speedo but I plan on getting my buddys gps to sheck it real soon. I went run it again today without changing anything to get an idea of how it ran, now tomorrow I will try it with my spare prop which is a 14 pitch and the one I have one it now is a 15 pitch Ballastic.

 

[steelespike]

Re: front of boat is plowing through the water

carefully check the bottom for a hook. maybe just a slight oilcanned area near the transom it might be just enough to cause your problem.<br /> You might try a long straight edge 5 ft or more along the bottom to see if it a slightly hogged.( a long gentle hook)

 

[Boatist]

Re: front of boat is plowing through the water

To raise the bow you trim the motor out, away from the transom. If what you mean by the "motor blows out" is that it cavitates then the motor is mounted too high. The prop need to be pushing water up and pushing the transom down to raise the bow.<br /><br />A hook in the hull can also cause the boat to not ride right.<br /><br />Too much weight up front will also cause the bow to ride low but with 40 HP if you trim the outdrive out away from the boat the bow should raise up even out of the water. If the props slipping when trim all the way out then you have the motor mounted too high.<br /><br />This should be very simple adjustment. I would not mess with the prop until you get your boat trimmed correctly and know you WOT RPMS.

 

[2004hemi]

Re: front of boat is plowing through the water

ok so I looked for a hook in the hull and didn't see anything, so I lowered the motor one hole today and went try it. Its a little better but still not like it should be, so I went to the dealer where I got my motor from to bring the prop back and they didn't have a 14pitch in stock so they gave me a different style 15pitch to try it lifted the front but the motor just didn't sound right at mid range so I guess I will wait till they get the other prop in next week.

 

[studlymandingo]

Re: front of boat is plowing through the water

What do you mean it did not sound right at mid-range? Do you know what your WOT RPMs are? That is the determining factor for prop sizing ultimately. If the engine got into the recommended range at WOT you may not need a different pitch.