Boat lists,porposes while on plane.

[alldodge]

While I cannot answer that question, all I say is proposing is caused by to much weight in the stern. As the speed increases the bow comes up and then drops. The distribution of weight over the boat is the key. Moving more weight forward off the stern needs to be done.

 

[Fed]

Here's an interesting comparison to yours I pulled off their website, check the height & see how the tunnel is open to the air.


I remember reading a thread about a guy who could intentionally hit a wave to get the hull to break free & it would then accelerate up to its full potential.

I know another guy who has pods with side skirts on a sharkcat, each side replicates your hull exactly and he is currently fitting infills to make the pods a smooth extension of the hulls (he also has heavier than normal motors fitted and his problem has not come up with standard weight motors, he's working with the boat builder to try & resolve it)

Interesting thread juicegoose.

 

[Tail_Gunner]

Pocket tunnel's are different from a deep v, you cannot trim them to sit on there keel and simply gun it down the water on it's tail so to speak... it does not have a keel like a deep v...Instead it has a water cololum that has been raised allowing one to raise the motor read less drag and allow the boat to ride on its outside sponson's..The rev 4 has high rake...read high bow lift....running deep....setback...read again weight shift going towards the transom..... its trying to dance but cannot...... it simply lifting and falling off the rear pressure wave.

The answer I am sure of is to lift the engine to its maxium height and finish it with a cleaver type aka the txp..they provide overall lift and fight bow lift..... they will lift the entire boat..on the sponson's where the hull was designed to run at. and the porposing should be reduced.

Below is a pic where the boat does have a deep v and a keel to support it dancing down the water.... notice how deep the trough is about 18" deep.... the boat is balanced on the back two feet of the keel. a tunnel hull will not do that it cannot there is no support.

 

[juicegoose]

I agree guys with everyones statement. I've accepted the fact that the tunnel is just a different beast. Again I think a lot of my issues were that I was expecting it to act like a deep V bay boat. It can't as you all have stated. I know the newer nautic star tunnels have pods on either side of the hull that extend past the transom some. I'm sure this is to help.

I also had a chance to speak with another 2110 owner that has a Yamaha 200 HDPI installed. He indicated the same characteristics that I have shown but didn't think it was a problem just the limitation of the boat. Big motor, light hull, short length, narrow width. He indicated he had a 3 blade prop(was gunna check the pitch this weekend) but he could get 58-60 WOT. Now this is is different engine and I think his is a standard model without the tunnel or bottom paint so that speed seems about right. He did also say that the 3 blade wouldn't grip well in turns where ass my rev4 loves the turns.

Also spoke with my local prop guy (he's a turbo dealer). He said to run the boat again to verify top end rpms and then bring him the prop and have my needs firmly set. His advice was this.
"I can sell you or have you test props all day long but if that prop isn't slow to get you out of the water with your typical load and you like the performance of it in turns then why change. Your not going to be hitting the bay WOT very often and we are talking about chasing 2-3 mph. He also stated that placing a prop on the boat that gave me best performance with full fuel and 2 guys might be horrible with 5 adults and half fuel. He did think that we might be able to increase the pitch some if I wanted a little more speed but that the benefits would be negligible. Bottom line was to get a prop on the boat that best fit my needs.

My needs
Prop capable of getting 5 adults and 2 kids with fishing gear and full fuel around the bay comfortably. I think the rev4 is doing that I'm simply chasing perfection.
I rarely go WOT normally cruise around 3500-4500.

 

[Tail_Gunner]

Your prop guy is right about playing around with props...but what you do need to do is find where the engine starts's to pull down. So grab some sand bags fill them to duplicate your expected load....put that rev 4 on and see where your rpm come's out at..... if it still pulls to 5400 whiich it may very well do so and should do so you will have awnsered a lot of question's

Here are something's that dont make sense
1. Both the 17 and 21 run the same rpm
2. 200 hp eninge 1.75 gear's 17p rpop and that turn's only 5400 rpm on a light boat???.....Think 23/26 pitch props
3. Using a 24 would have shed light on the whole story so to speak either your tach or wiring is off or that hull has tremendous drag....which could be possible due to the suction of the tunnel i guess. Or a dirty hull will pul down a boat as much as 5 to 10 mph.
4 On higher Hp engines i found propping a enine up to it's intended WOT and calling it a day is not always the answer but propping down from the WOT will find where the engine's working hard or at peak performance. Finding where you have good tourqe and rpm

 

[juicegoose]

Thanks for the reply gunner. I'll have a full load on the boat this weekend and I plan on double checking the WOT rpms again. To answer a couple of your concerns.
1.
The 21p prop has had an 1-1/1/2 removed from it's diameter. See the attached picture. When I measured the diameter of the OFS3 it was 14.25" It is supposed to be 15.5". For reference the 17p rev4 is 14 5/8". That would explain why I was able to get similar rpms out of the prop. Heck it is possible that the 21 has been tuned to something other then 21p too. I use it as a spare prop now so it just sits in the boat.

2. It is possible that I could be off on my rpms some. My analog gauge always reads about 400rpm low and my digittach was acting up some at higher rpms. I will re-verify the rpms this weekend.

3. My boat isn't going to ever be a speed boat. The tunnel, bottom paint, and general design of a center console won't let it get going super fast. That's Okay though I'm not looking for top speed I'm looking for efficient cruise. If a 19p rev4 or ofs4 or turbo gets me the stern lift I need and performs as well as the rev4 has(hole shot, holding ability) then I'm happy.

 

[juicegoose]

prop pic

 

[Tail_Gunner]

Yes true tach rpm is critical it would place you in a whole different prop level. The turbo xp series starts at 21p and has some very big characteristic's you need.... there over all lifter's... not a bow lifter... and not stern lifter's...stern lifting is what you have now and is one of the root cause's or your bouncing and may very well be a hidden issue with your drive tourqe....Turbo lighting would be the next step...Don't let the diameter of the prop fool you..it's pitch that pull's thing's down

 

[juicegoose]

Well i got out on the water today with a 19p turbo os1 prop. Had similar loads as before. 2 men 3/4 fuel. Light winds. One thing i did do different was i had my friend raise the jackplate from full down until i felt the anti vent plate was just skimming the surface. This ended up being 4 on the jackplate. I did not go wot with the jackplate Ll the way up. I feel like it was inducing some slip and skewing my numbers. I tested both my rev4 17p and the turbo os1 19p with the same setting. Here was the results.
Rev4 17p
Seemed to lift my bow as ive stated before. Steering stayed heavy even while trimmed out. Top speed was 45-46mph at 5500 rpm.

Turbo os1 19p
I loved this prop. The boat just felt better. I was able to untuck the motor a lot more the. The rev4 and even then the bouncing was only slight. Steering felt nice and light through the entire range. There was obvious pep in the prop im asumming from the 2" more pitch. Here is the downside though. Full speed was 45-46mph(same as rev4) but could only get the motor to 4800-4900 rpm.

I think im going to swap my prop for a 17p turbo os1 i really liked everything about it but 19p was to much.