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GBPackerNut

Four Stroke planing problem???

28 posts in this topic

Ok took the new boat out for the first time last night. Had some problems planing.

This is my first 4 stroke, so maybe the way it sounds and operates is different, I don't know for sure. I tried about 6 or 7 test runs, at different trim levels to make sure that wasnt the culprit. It is a Alumacraft Yukon 165, with a Yamaha 40HP four stroke. I tried to look at the prop but I cannot figure out what pitch it is.

When I go to open it up, she lifts the bow like its trying to pop up on plane, but just short, the motor sounds like its almost dogging a little bit as the rpms slowly increase the speed ever so slowly increases also until after about what feels to be 30 seconds or more finally she pops on plane and boom its like the after burners kick in and the motor finally starts winding up, and were moving along at a really good clip. But I cannot tell if were getting up to full operating RPM's though, this motor sounds so different to my ear its hard for me to know.

Does it sound like I just have too much prop, and need to change pitch? or is this normal for the newer 4 stroke motors?

Also does anyone know how to connect a tachometer so I can check the operating RPM's?

I will bring a stopwatch and gps along on the next outing to get actual speeds and times.

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Without being there its a little difficult to diagnose but two things come to mind. First, your trim angle. You did not say if it was power trim, I will assume it is. You want to start out with the motor trimmed all the way in (down). This "forces" the back end up and front down which pops you up on plane quicker. Once on plane, you will want to trim your motor out (up) until (absent a tach) the steering get's light and neutral - you will be close then. In waves or making a sharp turn, you will want to bring the motor in (down) a bit. If no power trim you will have to compromise - in this case I would set the cavitation plate so it is about parallel with the bottom of the boat. The second thing I would look at is prop pitch. If too big a pitch, your hole shot will not be good and you will lug the motor (it's like starting your car in second or third gear). This is hard to correct without a tach as you want to run at the max RPM's for your motor with your normal load. That way if you add a person or gear you will only drop down into the min range. I.e. - if motor is 5500 - 6000, with normal load shoot for 6000. Absent a tach there are prop folks who could probably get close based on the boat type, weight, etc. Hope this helps. Paul

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Good post PT!

I will agree in that from the description of dogging while trying to get on plane, then taking off and winding up, that it sounds like the motor is trimmed or set too high. Try trimming or setting the pin in (closer to parallel to the bottom of the boat, as PT mentioned) and see if it planes off any easier. If it works it's an easy and cost effective fix!

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Yeah it has power trim, I tried it all the way down, and several other angles just to make sure,

I was loaded pretty normal for how I am going to use it, maybe the boat is propped for the previous owner. I added one more passenger (225 pounds) and another trolling motor (45 pounds) plus I probably weigh about 50 pounds more than the previous fella.

Here are the boat specs

2006 Alumacraft Yukon 165

16'6" length, 76" Beam, 725 pounds dry

2006 Yamaha F40TLR

Weights

195 Motor

55 Fuel

150 Batteries

20 Charger and wiring

45 Vector trolling motor

45 PowerDrive trolling motor

25 Anchor

75 Misc Gear

450 People in the boat

====

1050 Weight of all items not including the boat

+725 Dry weight of boat

====

1775 pounds total weight.

So I don't think I am loaded too heavy, as I am still 400 pounds under its rated capacity, and the boat doesn't seem sluggish once I am on plane.

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If you tried starting out with the motor all the way in and still not getting on plane easy then you may need to look at propeller pitch. Your "normal" load does sound quite a bit heavier than the previous owners - it also sounds like you may have added a significant amount of that weight more to the back of the boat (additional passenger, your add'l 50#'s, not sure on the trolling motor or batterie(s)). This is also not going to help you pop on plane quickly. For context, I hit my max RPM's for my normal load (me, 1 livewell (30 gal), all my gear and full tank of gas) - if I add 2 people and their gear I am about at my min. Depending on what RPM the previous owner was running at - you may need to go down pitch angle or even two on the prop. You may also want to try to shift some of that weight forward (if possible). Owning two props is not the end of the world, one for lighter loads, one for heavier loads - use the other as a spare in case of trouble. One thing I can say for sure - you definately do NOT want to keep lugging the motor (if that is what you are doing), eventually you could do come damage that will be expensive. Good Luck. Paul

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Well I went home, I think I am pretty sure its over prop'd

Pulled the prop off and its a 10" diameter x 15" pitch, which is pretty aggressive for my boat combination.

Most of the reviews I have seen are guys using a 12" pitch prop on a similar style boat.

so now I need to figure out if I want to step down to a 12 or 13...

Darnit, I was hoping I wouldn't have to spend more on a boat I just bought 2 weeks ago...

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See if the dealer will be willing to swap it out since they should have given you a little more direction in this area. Hopefully you haven't found any rocks with the prop yet.

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If you bought the rig from a private party, call Alumacraft/Yamaha dealers and ask what the right prop would be. I'm sure there are quite a few sold in that combo. Dealers might be a little testy right now---the week after opener can be kinda crazy.

However, there is no substitute for having a tach in the boat--you will know for sure you are propped right (being at or close to max rpms, and not overrevving). The 40 is a sweet motor but with your boat loaded, it will need to be propped right.

Good luck.

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I.e. - if motor is 5500 - 6000, with normal load shoot for 6000. Paul

This got me thinking. I have a 2007 Merc. 4-Stroke. According to my owners manual, my motors max. RPM range is at 6000. It also says that WOT should be 5500-6000 RPM. Now, I run right at 5400-5500 RPM at WOT. Would one think I need to change out my prop (I.E. to gain that additional 500-600 RPM)?

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steffanf, It sounds like you are running pretty good as is. To swap the prop in an attempt to gain a couple hundred rpm will be a costly outlay for relatively little performance gain. What performance criteria would you like to improve; top end, load carrying, hole shot, other?

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I had the same problem only with a 60 yamaha on a navigator. The solution was a different pitch on the prop and the motor raised on the transom.

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a hydrofoil works great for planing all boats including overweight underpowered rigs (four strokes). If u get propped right and it still won't plane well this would be your best option.

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a hydrofoil works great for planing all boats including overweight underpowered rigs (four strokes). If u get propped right and it still won't plane well this would be your best option.

Probably the cheapest and easyest way to fix (minor) planeing issues. A Hydro runs about $50, and is very easy to install.

Sounds like your issue is getting out of the hole. On plane your ok. I would go this route first, then worry about buying a new prop.

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Sounds like something needs to be done / changed, but I'm hoping you've done the proper break-in on this motor before all this. Good luck.

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New prop on the boat was just too much prop.

Will test this weekend hopefully, it should be here today.

Break in, I hope the previous owner broke it right also. only time will tell.

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steffanf, It sounds like you are running pretty good as is. To swap the prop in an attempt to gain a couple hundred rpm will be a costly outlay for relatively little performance gain. What performance criteria would you like to improve; top end, load carrying, hole shot, other?

That's kind of what I thought... everything seems to be OK. With the current prop I have on now, I have no problem getting up on plane. The top-end speed looks good too (no speedometer, so not exactly sure). I just want to make sure it's not running incorrectly at just the 5400-5500 RPM that I get now.

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I think you'll be ok here as well... if you dropped some prop pitch you'd get a better holeshot and a slightly slower trolling speed, but lose top end. If you're satisfied with your holeshot then I'd stay where you're at.

marine_man

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Thanks, m_m. That gives me some confidence that I'm OK...

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It seems a little under powered to me. That a good size boat for only a 40 HP motor.

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Originally Posted By: GBPackerNut
New prop on the boat was just too much prop.

What did you end up going with for a prop?

marine_man

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4 strokes have a history of not getting on plane fast. A lot of people when buy boats try to save a buck and get a smaller motor.

The first boat I bought had a 40 HP what a dog. When you have more than 1 person in the boat. I got a 50 HP and it was like nite and day. You see a lot of boats for sale with less than max. HP on them. Thats why they are for sale.

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Planing problem fixed.

New Solas 11.4" dia X 12" pitch prop works like a charm!

With full load she lifts real nice now pops up on plane, no problems. And we get about 36 to 38 mph according to my Lowrance sonar (has a little wheel sensor that is on the transom) and the RPM's sound about right.

And if I am out all by myself, and take some gear out( remove 500 pounds or so) , I am getting close to the RPM limit but not over revving it.

I understand what you are saying Charley, and yes it would be great to have a 50 E-TEC or opti (if they made one that small) but really a 40 on my boat is fine. And yes a 50 would be a 25% increase in power, it would be like going from a 100 to a 125...

I personally feel a 40 is fine on the boat I have, really no good reason to spend a bunch more money to only gain a few mph on the top end.

And anyone looking for a prop, give Jay at Soderblooms a call, he was right on, told him which boat, motor, weights and all, and he hit the nail right on the head!

Thanks m_m for getting me his info.

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And we get about 36 to 38 mph according to my Lowrance sonar (has a little wheel sensor that is on the transom) and the RPM's sound about right.

Sounds a bit optomistic on the speed, but I'm glad you got it figured out.

If you don't mind, how much did that prop cost you?

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