208 Adventure Top end

[jason808]

Hi All,
I just purchased a used 2020 Adventure 208. It is a beautiful boat, and super stoked to have found it. It is the biggest 20 foot boat I have seen so far

I took it out today with a full tank and only my wife and kids. It struggled to get on plane and I could not get it past 30 mph. It has a Yamaha F200XB with a three blade prop with a 14 1/4” diameter 17 pitch prop. I played with the trim tabs a bit, and the engine seemed like it was struggling the whole time.
The winds were blowing a good 15-20, so that might have been it.

Do you all have any recommendations on what I could change or adjust?
I do not care about going past 25mph, but would be nice to have more pickup at lower speeds.

 

[HookUp]

A 208 with a 200HP motor should have NO problem getting on plane with only 2 adults and kids. Despite a little breeze
Something aint kosher -
Wrong prop?
Water in the bilge (weight)
Tabs in wrong position.
My 208 with a 175 gets up on plane instantly with 3 adults and all their fishing gear for the day

 

[trapper]

jason, I have a 2006 208 with the same outboard WOT 42 mph running a Reliance 141/2 x15p blade. Also have T8 kicker on the transom.

 

[kirk a]

What RPM's was the motor maxing out at?

 

[Doc Stressor]

You definitely have a problem. Your engine should be able to turn at least 5500 rpm with that prop and get you a least 40 mph with that prop. GW performance data tends to be a bit optimistic, but here is what they got with your setup minus the hardtop and bow pulpit:

208 Performance Data

A hardtop can slow you down, particularly with a headwind, but you should be able to pop right up on plane.

Start with the obvious:

1. Look for excess weight such as a flooded forward of aft bilge.
2. Check how the engine is mounted. If it is too low and the anti-ventilation plate is underwater when on level plane, the engine will need to be raised to a higher position for proper performance. Boats are often sold with engines mounted too low.
2. Forget about the trim tabs when getting on plane. Tuck in your engine trim when starting out and trim out and as you start to get up. Some hulls will struggle to get on plane with the engine trimmed all the way in. You need to find your sweet spot.
3. As mentioned, you need to record your rpm with the boat on plane at WOT. You should be getting at least 5500 rpm. If everything else checks out, you could benefit from going to a 15" prop.

How does the engine sound? If you are missing on one cylinder, you will have poor performance. You can often see evidence for this by inspecting the spark plugs. All 4 should look the same. If one is cleaner or dirtier than the others, suspect an ignition problem that could be due to a bad coil or wire.

A fuel flow is the next thing to suspect but eliminate the simple stuff first.

 

[DennisG01]

Aside from possible machanical problems with the engine (yes, you should be able to run better than you experienced)...

-- Has the boat been sitting in the water? Does the bottom have ANY growth on it... even just a thin layer of slime?
-- Did you start out with the engine trimmed FULLY down and then bring the trim up to get better speed?
-- When you went for full speed, did you have the throttle fully pegged?
-- What were the max RPM's?
-- Lastly, are you relying on the boat speedo or GPS?

 

[luckydude]

This is perhaps not that helpful, but Grady claims a top speed of 47mph for my 228 with a 250. I've had it at 45mph on the Pacific (it was a very flat day). I could easily imagine that on a flat lake, no wind, you could hit 47. I said the Pacific was flat, flat is relative. It's never flat like a calm lake.

 

[jason808]

Thanks all,

It maxed out at 4000 RPMs
There was no water in the bilge
The engine sounded loud, but I did not hear knocking.
The engine has less than 20 hours on it, and no faults.
The hull is clean and looks brand new.
The speed was gps speed, I did not see another speed in command link box.
I adjusted the trim a little, but could probably do more.
The throttle was all the way down forward.
I have attached pictures of the mounting height.

 

[MA208]

Will it tuck in all the way with the trim all he way down?

 

[jason808]

Will it tuck in all the way with the trim all he way down?

Yes it will, on the trailer can’t get it lower or it cuts into the ground.

 

[seasick]

First thing to check is that the throttle linkage on the motor is moving all the way to open throttle when the lever is pushed forward. Do that with the motor not running.
4000 revs WOT is way too low for that motor.
Many possible causes but some more common than others. Assuming the motor isn't surging when it maxes out, the issue is probably not fuel flow. It could be a wrong prop or loss of spark. You can test spark with an inexpensive tester from harbor freight. Note that some motors turn off certain cylinders at lower revs so check spark one by one at the dock if possible with boat tied off and in gear .Check for spark at about 2,000 revs.

I am not sure of the LU gear ration off hand. I need to check but regardless it should be revving higher. How did you determine the pitch? The number stamped on the outside of the hub may not be the specs , especially if it is a single number like 17M.

If you start from a stop and jam the throttle way forward, do the revs increase uniformly or do that increase rapidly without a corresponding increase in speed?

Did the boat ever make more than 4000 revs at WOT as far as you know by experience.

 

[jason808]

First thing to check is that the throttle linkage on the motor is moving all the way to open throttle when the lever is pushed forward. Do that with the motor not running.
4000 revs WOT is way too low for that motor.
Many possible causes but some more common than others. Assuming the motor isn't surging when it maxes out, the issue is probably not fuel flow. It could be a wrong prop or loss of spark. You can test spark with an inexpensive tester from harbor freight. Note that some motors turn off certain cylinders at lower revs so check spark one by one at the dock if possible with boat tied off and in gear .Check for spark at about 2,000 revs.

I am not sure of the LU gear ration off hand. I need to check but regardless it should be revving higher. How did you determine the pitch? The number stamped on the outside of the hub may not be the specs , especially if it is a single number like 17M.

If you start from a stop and jam the throttle way forward, do the revs increase uniformly or do that increase rapidly without a corresponding increase in speed?

Did the boat ever make more than 4000 revs at WOT as far as you know by experience.

The prop has
17-M
14 1/4”
Stamped on it , is the Yamaha saltwater reliance series.

I will work on checking the throttle linkage today.

Thanks!

 

[DennisG01]

Gotta keep trimming to up to get a realistic top end speed. W/O doing that, it causes more guessing.

What about my second question?

Are you POSITIVE it's GPS speed? I don't know your head unit very well, but just because a speed is shown digitally, doesn't mean it's sourced by GPS. Given the 4K RPM's, 30MPH sounds about right - but it would be good to know for sure, one way or the other.

 

[jason808]

Gotta keep trimming to up to get a realistic top end speed. W/O doing that, it causes more guessing.

What about my second question?

Are you POSITIVE it's GPS speed? I don't know your head unit very well, but just because a speed is shown digitally, doesn't mean it's sourced by GPS. Given the 4K RPM's, 30MPH sounds about right - but it would be good to know for sure, one way or the other.

The speed was from the gps in the navionics app, which i have verified to be pretty accurate and also on the onboard humminbird.

I trimmed up some but could have done more, the boat really seemed like it was struggling.
Spoke with one of the local Grady Adventure owners, and he mentioned the same. Looks like I need to get more hours on the boat in some other conditions, and write down the speeds at different rpms to get a better idea of what is happening.


Does anyone else have any pictures or know what hole their engine is on?
My engine is on the second hole from the top

Thanks again!

 

[DennisG01]

OK, that's definitely GPS. The reason I was double checking is that "pitot" hole speed can be converted to a digital number on a display - yet the data for the speed still comes from the pitot.

What about my second question... especially the first part? You are fully reading our questions, right?

Your engine appears to mounted correctly. The anti ventillation plate looks to be slightly higher then the keel. That looks good.

 

[seasick]

The speed was from the gps in the navionics app, which i have verified to be pretty accurate and also on the onboard humminbird.

I trimmed up some but could have done more, the boat really seemed like it was struggling.
Spoke with one of the local Grady Adventure owners, and he mentioned the same. Looks like I need to get more hours on the boat in some other conditions, and write down the speeds at different rpms to get a better idea of what is happening.


Does anyone else have any pictures or know what hole their engine is on?
My engine is on the second hole from the top

Thanks again!

More important than the hole (2nd is the rigging default I think) is where the anti- ventilation plate sits when on plane which in your case may be an problem maintaining.
Experiment with the motor trim with no trim tabs applied as a start. While on plane or there abouts, take a look over the side and see where the spray is coming off the hull. If too far forward that would mean that the bow is plowing and the motor needs to be trimmed up ( of some other motor angle issue).
Since this problem may have been there before you purchased the boat, it might be a bit harder to narrow down the cause.
I looked up the specs and the LU ratio is 1.86
With no slip (impossible) at 4000 rpm theoretical peed would be 34.6 mph. Add 10% slip and you will get 31 mph approx. Your speed is in that range for the revs, so the issue is why the low revs?

The motor should have an SDS prop according to Yamaha description but I don't know if that makes a difference on speed or just shifting.

 

[jason808]

OK, that's definitely GPS. The reason I was double checking is that "pitot" hole speed can be converted to a digital number on a display - yet the data for the speed still comes from the pitot.

What about my second question... especially the first part? You are fully reading our questions, right?

Your engine appears to mounted correctly. The anti ventillation plate looks to be slightly higher then the keel. That looks good.

@DennisG01 thanks for confirmation it is mounted correctly.
I thought I answered your second question.
I had the motor fully trimmed down, and then raised the trim while at full throttle. I did not raise it too much because the boat was not responding as I have experienced with other boats.

I have to put it in the water tomorrow, and will take better notes of the response.

I greatly appreciate the help, this place is awesome

 

[DennisG01]

@DennisG01 thanks for confirmation it is mounted correctly.
I thought I answered your second question.
I had the motor fully trimmed down, and then raised the trim while at full throttle. I did not raise it too much because the boat was not responding as I have experienced with other boats.

I have to put it in the water tomorrow, and will take better notes of the response.

I greatly appreciate the help, this place is awesome

Different boats respond differently to varying amounts of trim. Sometimes quite dramatically different. Some boats plane better than others, some run through chop better. Get some time on the boat and hopefully the problem you're having is simple "user error"... which is a good thing since the "fix" is a freebie

I will mention, though, that if you had the engine trim all the way down AND you had the tabs all the way down AND you feathered the throttle to full (or close) there should have been VERY little bow rise. You should have absolutely zero issues getting on plane. Really, with a light load, you shouldn't even need the tabs. Let's see what happens after you play around some more

Not sure if it was mentioned above... but pull your spark plugs and "read" them. Label each one and then put it back in the same hole.

 

[Doc Stressor]

Yep. At this point, a dropped cylinder is becoming more likely.

BTW, isn't the engine under warranty? Why not let an authorized Yamaha mechanic take a look at it?

 

[enfish]

Yep. At this point, a dropped cylinder is becoming more likely.

BTW, isn't the engine under warranty? Why not let an authorized Yamaha mechanic take a look at it?

Yep, I'm in agreement with Doc. 4000 RPM WOT is way too low and is about the top end drop I'd expect with a cylinder not firing... Could be something simple like a bad spark plug or loose spark plug wire.

FWIW, I have a different motor, but many years ago I had just had the motor serviced which included new spark plugs. With less than 10 hours on the plugs, we were cruising along and the motor all of a sudden lost power and we couldn't get more than 4200 RPM at WOT (normally it is 5300). Back at the dock, the first thing we did was put the old spark plugs back in which solved the problem. So whether it was a bad plug or a wire wasn't popped onto a plug properly at the shop, I will never know. I just bought another set of plugs and swapped them out since I didn't want to waste the time trying to figure out which plug was bad, if any.