Am I plowing?

[91rr]

Does this look like the bow is plowing? I am at WOT at this point and it just seems like the boat should be going a bit faster. I'm not sure of the weight, it is a pretty heavy boat though. I have a brand new 5.7 with an OMC Cobra I am only getting 4400 rpm @ 35 mph with a 17 pitch prop. I added smart tabs right before the pic was taken and helped tremendously on the low end. It definitely feels like I am up on a plane but looking at the pic now I donno. Here is another shot with the boat just sitting.

 

[americaneagler77]

Re: Am I plowing?

looks to me like you are, heres my boat at about 3/4 throttle 34 ish mph properly trimmed on calm water.

 

[ziggy]

Re: Am I plowing?

yer planing, but yer bow down to the max. ya got power trim on that omc... ya need to bring the drive up/out. lifting the bow out of the water more.

 

[91rr]

Re: Am I plowing?

It is trimmed out all the way. Any more and the prop will come out of the water. Maybe an adjustment is needed on the smart tabs?

 

[guy74]

Re: Am I plowing?

It's plowing, I would guess you need to lighten the tension on the smart tabs.

 

[geneseo1911]

Re: Am I plowing?

How big is that boat? It looks like a 16 or 18. I would think with a 350 you should be able to run 50. I have a heavy old 18' deep vee with a 260 Merc. and it runs 47@4100 with a 21 pitch. I'm not sure if it's normal for deep vees to plane like that. I can't seem to get the bow of mine to come up with the trim, but I haven't seen it from the outside either.

 

[ufm82]

Re: Am I plowing?

Are you looking at a trim gauge or do you know the L/U is fully trimmed up? Even with tabs if the L/U is up that far it would be obvious in your picture. AND the boat would be porpoising like mad. You're not getting any of the hull out of the water. Something's amiss here. If the tabs were pushing up hard enough to stuff the bow while the prop was up far enough to be "almost out of the water" the boat would be unmanageable.


Add to that a 5.7l properly running on a 18'-19' boat like that should be hitting 50! Either that or running a ton of RPMs at 35mph. While the engine is new is it running properly? I could run almost 50 mph in a 21' cuddy with a 5.0L I owned several years back. It weighed more than your boat does. That thing should scoot with a 350 Mo-Sheen in it.

I'm suspect...

 

[Don S]

Re: Am I plowing?

It's really a simple to find out if you are plowing or not.
Get up on plane like that, then start bumping the trim out to bring the bow up. Watch your speed and rpm. If they both go up, you were plowing. Keep bumping the trim up until the speed starts dropping and the rpm's go up. You are now trimmed out too high. Trim back down a bump at a time until you have best speed and best rpm and the boat does not porpoise, then you are at best trim. Don't waste your time looking at the gauge, it changes with weight and loading, speed, wind and wave conditions. It's just something you constantly check and adjust for.

PS: Once you get used to this, you don't even look at the tach and speed, you feel it and hear it. It becomes something you do without even thinking about it.

 

[jigngrub]

Re: Am I plowing?

What year model boat is that?

Have you checked it for waterlogged foam?

 

[ma glastron]

Re: Am I plowing?

I would also try a 19 or 21 pitch prop.

 

[Cincyrunner]

Re: Am I plowing?

Looking at the photo, it does seem that the bow is too far down into the water. Do you get a lot of water spray in that condition? Since you have smart tabs, I'd look at those first.

 

[nlain]

Re: Am I plowing?

From my personal experience, I ordered Smart Tabs with the 80 cylinders, I could not get the boat bow out of the water, I called Nauticus, they sent a set of 60 cylinders and with a couple adjustments all is good. Just a thought.

 

[91rr]

Re: Am I plowing?

I definately think the bow issue is related to the tabs. I can trim it out all the way until the prop comes out of the water without really changing the bow height. Before the tabs I could trim it out nicly. I just never saw a picture of it before so I really don't know how it looked. I can say that my top speed has only dropped a couple of mph with the tabs. I am at over 5000 ft and have the high altidude gearing in the outdrive if that makes a differance in my top speed.

 

[90stingray]

Re: Am I plowing?

Disconnect tabs and see what she runs... like stated earlier, you may need the 60# actuators. Boat should run closer to 50mph.

 

[southkogs]

Re: Am I plowing?

I don't know if this helps the conversation any, but this past weekend we were out on the lake and saw a boat running along looking roughly in the water like your photo. I thought he looked low, but he was outrunning me at 35MPH. Never saw the make of the boat, but maybe it's just the hull design?

 

[ponchoman]

Re: Am I plowing?

My 93 Glastron looks exacly like that. For me I'm thinking it's a prop issue since mine has no cup and little rake. I would remove the tabs and take it from there. They just force the bow down.

 

[jdlough]

Re: Am I plowing?

I would also try a 19 or 21 pitch prop.

I may be wrong, but I think this is exactly backwards. At WOT you're only getting 4400? I'm guessing you should be between 5000-5500?

If so, you need to lower the pitch, to a 15 or less.

Probably the bigger deal is that your Smart Tabs are set too stiff, as guy74 says. Move the shock rod in to the closest hole on the tab to the boat, to lower the stiffness. Your tabs may be too big for your boat. Call Nauticus for advice. They're great.

Oh, and re-read Don S's post a couple of times.

 

[smokeonthewater]

Re: Am I plowing?

Don't change pitch up OR down unless you find more rpms somewhere .... You are right where you should be at 4200-4600 rpm
ALSO guys, he said he only lost a couple mph with the tabs so he won't be hitting 50 by adjusting them.

 

[tswiczko]

Re: Am I plowing?

Aluminum or Stainless prop?

My boat plows with the tabs up all the way when I use an aluminum prop and drive position doesn't make a difference.

The ss prop gives me good bow lift.

 

[kahuna123]

Re: Am I plowing?

Why did you add the tabs???