Boat Won't Plane

[MGuckin]

18' Starcraft aluminum. 150 hp Evinrude.Full throttle launch achieves 51 mph @ 5000 rpm in 7 seconds (yup it's fast scared the s*** outta me), but the bow won't come down for about 3 minutes. Got it trimmed all the way down. Motor is mounted at the correct height. No jack plate. Spinning a 14 1/2 x 19 which should be the correct prop as it is not over reving.<br />I believe max hp is achieved at 5000 with this motor.<br />Already installed a Doelfin. <br />Any ideas?<br />Mike

 

[Capt DHD]

Re: Boat Won't Plane

Hello;<br />It should go like H**l! Sounds powered well.<br />Is there a tilt pin in the midsection? The Fast Track mid sections have about 7 settings. Check it you may be able to lower the angle. If you are out of tuck you may want to consider adding a set of wedges to increase your trim range. Not an expensive fix.<br />A little additional weight in the bow may help as well. Adjust & test, Adjust & test. <br />Good Luck...Capt DHD

 

[MGuckin]

Re: Boat Won't Plane

Not quite sure what you mean by wedges but I will try adding weight. <br />Thanks,<br />Mike

 

[Rex]

Re: Boat Won't Plane

CHECK YOUR TILT PIN. MAKE SURE IT ON THE <br />BOTTOM. ONCE ON TOP THE WATER SHE COME DOWN FOR YOU.<br /><br /> REX

 

[MGuckin]

Re: Boat Won't Plane

Pin is already in the bottom.<br />Thanks anyway.<br />Mike

 

[yensid]

Re: Boat Won't Plane

Well, trim tabs would help, but you shouldn't have to install them to get better performance than that. You could try using wedges to make it so you can trim it further down.<br /><br />Just curious, but how do you know it's mounted at the correct height? Just double checking, I don't really know about this one...

 

[yensid]

Re: Boat Won't Plane

*side note*<br /><br />Dhadley, how do you figure that out? By my math, it seems that 5000RPM with a 19inch pitch would be about 90 mph with no slip, which wouldn't be over 100% efficiency. But, I've never tried to calculate it out before so I may have screwed that up.

 

[Dhadley]

Re: Boat Won't Plane

This is interesting. It goes 51 in seven seconds and hangs the bow in the air for 3 minutes? How high are you talking about? Does anything else happen when the bow finally drops? <br /><br />The Starcraft is a very good (and light) boat but you should be turning well over 5000 RPM with a 19. At 5000 RPM it figures out to be over 100% efficient at 51.<br /><br />Keep us informed. Good luck!

 

[Dhadley]

Re: Boat Won't Plane

yensid -- you are correct, it would be 93 mph with a 1:1 gear ratio. Factor in the stock V6 gear ratio and we get back to almost 49. If we use the stock V8 ratio the speed goes to about 53 and slip changes to 3%. It would be very unusual (although not impossible) to see a V8 gearcase on a 150. But with that ratio I wouldn't think the acceleration would be as good as reported.<br /><br />Good luck!

 

[yensid]

Re: Boat Won't Plane

Thanks! I knew I was forgetting something, the gear ratio.<br /><br />Good, now I know how to figure that out

 

[suzukidave]

Re: Boat Won't Plane

You may be overpowered so the bow can't drop but the boat is eventually being jolted or bounced onto proper trim by a wave or something. I used to get the same thing on a light 12' aluminum rated for 8 horse with a 15 horse on it. Waves about six inches high would bring the bow down and then it would stay down. Weight in the bow definitely helped.<br /><br />If you can't adjust the trim any more on the motor have you thought about trim tabs? Nauticus makes automatic "smart tabs" for a boat that size that are fairly cheap. There are several positive reviews on the web (search "nauticus smart tab" on google.com). They sound like they might fix your planing problem (and make you go even faster!). By the way, is it possible your speedo is wrong on the mph you are achieving. 0-51 in 7 seconds is pretty nuts.

 

[MGuckin]

Re: Boat Won't Plane

Lets see if I can answer all questions.<br />Speed was clocked by an officer with radar.<br />Speedo on boat is not working yet.<br />Maximum rated hp for this hull is 150.<br />Michigan Prop says prop is a good size for this hull but pitch is a little much.<br />There were 2 people in the boat.<br />The plate (not sure what it is called, I'm just a backyard mechanic) that the doelfin is mounted on is even with the lowest point on the bottom of the boat which according, to what I have read and done in the past, is correct.<br />I think the boat should be faster but don't care.<br />Boat motor package weighs 1188 lbs. (Weighed on truck scale on trailer than trailer weighed and deducted).<br />Bow stays up too high for me to see when seated.<br />When bow comes down, finally, it approaches the 60 mph mark and smooth.( had a friend clock me in open water).<br />I also launched starting at 2000 in 500 increments to find its favorite spot.<br />Will not plane but is comfy @ 2800,could not check speed, but bow angle is such that I have to stand.<br />Sorry if it doesn't fit in formulas but I no nothing about formulas.<br />If you can make it do as fast as the Formula says, I will be scared but gratefull. I just am looking for a descent speed and comfort level. As the previous owner told me when I bought it, put on a seat belt.<br />Thank you,<br />Michael<br />ps: tach does work as far as I could tell and did not go over 5000.

 

[MGuckin]

Re: Boat Won't Plane

After reading the rest of the posts to my topic, I elected to delete it. Forum will not allow me to do it.<br />Thank you very much to the few posts that did attempt to help me and not ridicule me.<br />I am very sorry that my boat did not fit into your formula. I don't understand it either.<br />I told you what I had and what it did.<br />I thought it was a constructive query.<br />Yall take care.<br />Michael<br />

 

[markg]

Re: Boat Won't Plane

Mike,<br />Sounds like a great rig. Personally, I'd get rid of the doel fin because it just creates more drag in water (IMHO). Try rising onto plane with less throttle and more time. Three minutes is a long time for the stern to be squatted down. I agree with the writer who indicated the boat bounces onto plane. A 150 should have PT&T, I'd adjust that for different RPM and see if there's improvements. I can't see trim tabs on an aluminum hull unless you're running in some very angry water. I wish I had this problem.

 

[nickster]

Re: Boat Won't Plane

MCuckin!<br />Question, What are the water conditions and are you going with the water or against the water?<br /><br />Nick

 

[Dhadley]

Re: Boat Won't Plane

MGuckin -- what I wanted you to think about was your tach. Starcrafts are great boats and a lot of fun. If you are really turning more than 5000 (which you should be with a 19) everything falls into place. As a matter of fact you should be able to turn a larger prop than a 19. We usually run a 19 or 20 on the 21' Starcraft with a 150 and a 21 on the 18 with a V4. I have no doubt about the speed and believe you can safely get more. What brand of tach do you have? If it is the correct tach make sure it's set on position 6. A tach set wrong will do exactly what you describe. <br /><br />Let us know. Good luck!

 

[Fitch]

Re: Boat Won't Plane

Sound like a lot of good replies. Did you get it working yet? The foam in the floor isn't waterlogged by chance?

 

[clanton]

Re: Boat Won't Plane

Your first post indicates that you do not trim up. Try trimming up, bow should go down.

 

[MGuckin]

Re: Boat Won't Plane

Dhadley,<br />Can you explain why I would have to be reving over 5000 with this prop? I checked the tach as you suggested, set @ 6, and compared readings to my bench tach. It was close.<br />I do now have a speedometer installed and I put (3) 40lb. bags of sand in the bow. <br />Am trying tomorrow. I can always move the bags around and use PT&T to correct bow height if it drops to low.<br />After measuring where console sits (12' from the transom in a 18' boat), in relationship to the rest of the boat, I believe I do have a weight transfer problem.<br />Most of the weight is aft of the centerline of the hull.<br />If I understand the geometric priciples of tilt, to lower the bow, motor must be closer to the boat (perpindicular to the hull as opposed to parallel). Increasing the angle of the motor, aft of the boat, would actually put more force to lifting bow and, if too much, would porpoise or not plane at all.<br />I can't get any closer without a jackplate. Stop pin is in bottom hole and I am on it.<br />No foam is not waterlogged.<br />Thanks,<br />Michael

 

[Capt DHD]

Re: Boat Won't Plane

Hello Mike;<br />You sound a little "past" frustrated. Techs <br />here are just trying to give a few friendly suggestions. Chill.<br />Wedges are angled aluminum plates shaped like wedges (hense the name) that go between the engine mount bracket & transom. Allowing additional tuck (assistance lowering the bow)<br />Pretty simple fix, not expensive. <br />Try companies like TH Marine, Cooks Mfg. Land & Sea Inc. Your local dealer should know of these companies. <br />With the right amount of wedges you could bring the bow down low enough to make a "Starcraft Submarine" if you choose. <br />Try it, it will work.<br />Good Luck...Capt DHD.