boat running too flat

[drbobp]

I have a 1996 Stratos 285 Pro-V with a 150 hp johnson fast strike. I bought it used and have been having problems getting it to run right. My tach is still not working but I had the engine checked on a dyno and it is producing plenty of power (more than 150 hp). Here is my problem:<br /><br />When I run wide open, it seems too flat. The spray starts just behind my seat. When I let up on the throttle (foot-controlled), the bow lifts and the boat jumps up on the last pad. When I add gas, it drops back down.<br /><br />With full gas tanks and two people (I weigh about 200 and my partner weighs 300 pounds), it will run about 52-53 GPS mph. With just me, it will run about 54. The factory (and others) say this boat should run about 62-64. <br /><br />I think, that if I can keep it on the last pad, it will speed up. I have a 10" jack-plate and have moved the motor up as high as it will go (26 pounds of water pressure).<br /><br />I know that I have some nicks (not too bad) on the prop so that may be part of the problem. I have been told that a "hook" in the hull may cause this type of problem. <br /><br />How do I find out if I have a hook? I sent my old prop to be reworked and it looked beautiful when it came back but a friend showed me that it was "out-of-round" - that is, it wobbled a small amount when it turned. (the shaft did not wobble). I would like to get the one that came on the boat rebuilt, but don't want it to come back the same way.<br /><br />Suggestions? Thanks!

 

[Dhadley]

Re: boat running too flat

If the shaft is straight and you had the hub replaced in the prop then it may just need to seat. I wouldnt worry too much about that anyway. Just run it and see what happens. <br /><br />Your type of prop has a lot to do with it. Since you didnt tell us what you have lets look at the hull.<br /><br />We're not really sure what you mean by "the last pad" but it sounds like it noses over when it tries to get on the pad. The 10" jackplate suggests that this has been a problem for a while. <br /><br />Put a straight edge on the pad. Look at it from the back of the pad to at least 4' forward. If it has a hook there will be a gap from the pad bottom to the straight edge in the last few inches. With pad bottom boats we want the pad straight. We look for the hook to be in the hull but not in the pad. The further out from the pad, the more hook is OK. The closer to the pad, the less hook you want. 1/8" is a lot.<br /><br />Also you didnt mention if there are any type tabs. Is there anything aft of the transom where the jackplate is mounted?

 

[drbobp]

Re: boat running too flat

Thanks, Dhadley. The hub wasn't replaced...the blades were reworked to get rid of dings. The prop is a 24 pitch Raker. The bow jumps up when I let off the gas (while at full throttle) and drops back down when I add throtle. I don't have any trim tabs. I can still get about 50 mph with 4 good size adults in the boat.<br /><br />I'll look at the bottom and see if I have a hook. What can you do if there is one?

 

[Maximerc]

Re: boat running too flat

Interesting, sounds like your Bimiki top is a sail! Do you have a Tachometer in the boat?, wondering if your prop is not giving you any lift. Your boat being that new I would be hard pressed to say its a hull problem unless it was a factory defect. I have been fighting hopping at high speed , some one suggested that my engine was causing the hull to bow at speed. My hull is now being rebuilt and the stringers are bad and everything is soaked. So it is possible things are warping under power (the hull is flat on the trailer). Though simple the extra water in the wood/ foam is most likely the culprit. I tried a lot of things to correct the problem, trim tabs being one , but I kept thinking .. This boat did not perform like this brand new. I was pretty sure deep down what the problem was. No bandaides fixed it. <br /><br />I guess what I am saying is , look at everything.. overlook nothing. I hope its something less sinister than I am dealing with. Sure does drive ya crazy though.

 

[drbobp]

Re: boat running too flat

Maximerc, I hope you are'nt right....but, I'm afraid you may be. I had a leak under the rub-rail. It would take on water when coming out of the hole. Fixed it..but maybe the floatation is wet. Extra water and/or rotting. Yikes!!!!

 

[Dhadley]

Re: boat running too flat

Well, I was hoping we didnt have to go that direction but we may have to. Yes, when stringers become rotten or soft the boat will flex and do exactly what you describe. The key is going to be WHEN this started. If its been since new, we're probably kooking at a straightness issue. If it started when the boat was a couple years old or so, then we may be back to stringers.<br /><br />The Rakers have good lift and the 24 Raker has the most lift of all the Rakers. Good choice.<br /><br />Trailers play a big role too. A pad bottom boat should be supported by bunks that contact the hull but not the pad. If the pad sits on rollers the pad will become wavey and the boat will do all sorts of wierd things.<br /><br />So to start with lets look at the pad and then go from there.

 

[CalicoKid]

Re: boat running too flat

I don't want to insult anyone by suggesting the simplest of ideas, but are you trimming the motor out at speed? If it's tucked in you'll plow the bow down under power. Is everything tight and sound where your jackplate attaches to the transom and where the outboard attaches to the jackplate? Is there any kind of play back there? With the motor trimmed out and the boat on the trailer, can you bounce the motor up and down? That is, does something allow your motor to tuck back under when leverage is applied?

 

[Tom2697]

Re: boat running too flat

Calicokid,<br />I was thinking the same thing...<br /><br />This just came to mind...what HP is your jackplate rated to? It sounds as though you might be overpowering the hydraulic unit when you throttle down. Reducing the gas allows the jackplate to return to the normal position. Many jackplates are rated for "under 150 hp" and for over 150 hp". 150 hp is almost always the "magic number" with boats...<br /><br />Just a thought...

 

[drbobp]

Re: boat running too flat

The jackplate is a new one-piece rated for over 150 hp. I trim the boat through its full range and still have trouble keeping the nose up. So far I have come up with 3 possible problems<br /><br />1. the prop is dinged too badly and needs to be fixed (I will do this, but it really isn't dinged too much)<br /><br />2. the boat was taking on water (under the rub-rail) for some time before I figured out where the water in the bilge was coming from. The floatation may have gotten waterlogged. <br /><br />3. while water was getting in, it may have softened (rotted?) the stringers.<br /><br />I think my best course of action is to get the prop reworked, have the boat weighed to see if it is way too heavy, or (last resort) separate the top from the bottom to see if the stringers are rotted.<br /><br />Does anyone see anything else I could do? Thanks, all!

 

[drbobp]

Re: boat running too flat

By the way, my boat repair guy says that I don't have a hook in the hull.