Lithium batteries and lost speed?

[ZRT600]

I just switched to all lithium batteries, this weekend fishing a tournament I could only get 60mph@5800 rpm. I was running 65-69 same load before the battery swap.

2012 nitro z9 with a 250 pro xs and 8inch hyd jack plate, 1 talon, 25 pitch tempest 3 blade. I can get an inch or 2 up on the jackplate and I start to loose speed. Trim is maxed and rooster is about as high as the motor. I am at 25ish psi water pressure.

I want to get this prop worked but I want to have my set up right before I do... Before I put the lithium in I was maxed on trim and almost at the bottom on the jackplate. The motor is mounted as low as possible.

I will try to measure prop to pad tomorrow, but in the meantime any suggestions?

[John Jackson]

Are the lithium batteries the only change? IF so, you have other issues that just started. The only way this could slightly happen is if the batteries are behind the pad so you lose some bow lift. Even then, it wouldn't be a 5 mph loss.
Getting lighter will not slow a boat down (unless you are too light and running 120+ MPH)
You water pressure does indicate you need to come up with the motor. Check your prop for any damage and lower shaft for runout. If everything is OK, get your motor checked out.

[ZRT600]

Batteries are the only change and batteries are right at the back. This boat has always seemed like it needs more bow lift. I've never been able to bring the jackplate up to the point of getting below about 20psi. Prop is mint.

I have a feeling I don't have enough bow lift as it seems like it's riding with the nose to low.

[xb03fs]

Boat could be out of balance now that you have less battery weight.

[pmgoffjr]

Taking out weight will never slow you down.
Raising the motor too high will lose bow lift, not increase it.
As summer temps rise, your performance will decrease, cold air is more dense than hot.
Might be a good time to investigate trim extenders, if it's running that flat with a 250. I've seen nitro's with whacked out transom angles. *IF* your holeshot is good enough to allow that change.

[xb03fs]

If I take 50 lbs of lead shot out of the left side of my Allison when running solo, it will not fly straight. I will abosolutly only be able to run 83/84 instead of 89/90.. The alternative would of course me losing 50 lbs. But right now solo, the lead shot stays on the left and with a passenger the lead shot goes on my side and the boat is happy.

[pmgoffjr]

Which has nothing to do with a nitro.

[xb03fs]

Won’t all benefit from good balance. The more balanced the less steering corrections the straighter the sleg runs the faster it rolls

[ZRT600]

This picture is where I end up full trim. I trimmed up part way and took off, came out of the water no issue and right up on plain.

_20180604_145814.jpg

[pmgoffjr]

Let the boat tell you what it wants. If it's throwing a big tail and you're running flat at full trim, bury the motor some and see if you get some lift at full trim, if it's wanting more a $20 set of trim extenders will give you a quick test, if THAT works, then look at some transom wedges for a permanent fix.

[ZRT600]

Yeah that's about where I'm at right now. I'm about 4 inches below pad. Any higher and I have basically no bow lift and can't get any better than 55mph or so. I'm going to call around and see what I can find for wedges or extenders, see what's stocked locally.

Thanks :)

[gonnabe]

Try thinking of a bass boat as a see saw. The farther you put back that merc 250 the more lifting leverage you will have. I would buy some Bob's 2" spacers to add to the jack plate. You would be surprised what the outcome would be.

[ZRT600]

Hmm, I like that idea better than wedges.

[pmgoffjr]

Careful,
You can easily have too much setback. As your hull moves through the water, it creates a swell behind it, all are different length and height. You want to be just at the top, or just in front but never ever behind the top of the swell.

And it's apples and tomatoes, trim angle and setback distance, two inches of setback will maybe give you some lift, four degrees of positive trim will give you a lot.

[lpugh]

Less weight = less draft...… try dropping the motor a half inch. Losing 150 lbs on the back of the boat would have the same effect as raising the motor I think

[ZRT600]

It's already all the way down. I can go 1 hole lower on the motor but I don't know if the steering system will clear. I'll probably attempt that while adding wedges.

[lpugh]

Measure the P to P and report back
When checking it use a level on the pad and adust the tounge height to get the pad level Then put the level on the cav plate and level the motor. This asures better accuracy when checking

[ZRT600]

Measure the P to P and report back
When checking it use a level on the pad and adust the tounge height to get the pad level Then put the level on the cav plate and level the motor. This asures better accuracy when checking

4 1/2, but I've tried running it everywhere up to the point where I was down to just below 15psi waster pressure. At that point water spray is coming from in front of me.

[jt c]

Maybe before you start adding wedges and such try a different prop?

[ZRT600]

Maybe before you start adding wedges and such try a different prop?

I'm going to try my fury but before the battery swap it has worse bow lift than the tempest. That's why I picked up the tempest.