New Motor, boat now Chinning!

[Bisons1]

I recently purchased a 1999, 20ft Viper, Cobra. Had a 2009 Yamaha 250 Vmax, series 2. Upon test driving, the boat attained a speed of 70 mph (gps) in choppy water, with no chinning at 70. The boat has a hydraulic jack plate, setting the motor back 6"s from transom. When maxing out speed during testing, the jack plate was set about 1-2 "s above transom. When on plane, we raised the jack plate to about 5"s above transom, and trimmed up. thus attaining 70 mph with no chinning.

Purchased boat, went home. 12 hr drive. Yamaha turned out to be a lemon ( another story ).

Purchased a 2014 Evinrude 250 E tec. with a 14.25 x 23 pitch, stainless steel prop. mounted on the jack plate, ( jack plate was not adjusted ). Got it back home ( 8 hr drive ). put it on lake, with max fuel ( tank runs behind the seats, even weight distribution ). Had a buddy in the passenger seat, myself in driver seat. ( he out weighs me by about 30 lbs ). Had the motor lowered even with transom for hole shot. Got up on plane very quickly, started to trim up. started chinning at about 5000 rpm and 55 mph. slowed down, readjusted the jack plate.. started raising it inch by inch,( ended up 8"s above transom ) while trimming.. was able to attain 63 mph ( gps ) at 6000 rpm ( max throttle ). No faster, but wasnt chining. down side. when attempting to steer left or right, prop was so high up, that it would seem to come out of the water ( over rev prop ). This boat and motor should be attaining 70-75+ mph with ease. I can t figure out what the issue could be. any insight would be greatly appreciated.

thanks.

 

[jimmbo]

I don't suppose you got an owners manual? If you did, what does it say about warnings? What are your water pressure and temp readings? You bought a used engine, any info on its history from the previous owner? What prop are you running? Is it one designed for high engine heights?

In what way was the yammy a lemon?

Edit: "Chiming". Did you mean Chine Walking?

 

[Chris1956]

You were using different style props, right? Some props hold the water better when trimming or Jacking, and allow more speed. Maybe the Yammy prop on the e-TEC will work better, with the right pitch and hub.

If you do an analysis of the difference in gear ratios, between the two motors, you can determine the equivalent pitch for both motors. If the Yammy prop is a modular, and the right pitch, you maybe able to get am E-Tec hub for it.

 

[Bisons1]

Yes Chinning Jimmbo. The Lemon Yammy is not worth discussing.

250 E tec. with a 14.25 x 23 pitch, stainless steel Viper Prop.

Dont know what the Yamaha prop was, didn t stay on my boat for more then a few days...got rid of it awhile ago. I have 2 other stainless steel props that are 25 p... I'll look into whether or not they are compatible.


I did notice today on the water that the boats transom has some flex. wondering if I might have an issue with it.. and when I hit higher speeds it puts more pressure on the transom, causing it to allow the motor to walk?

 

[jimmbo]

Usually the highest time of stress on a transom is climbing on to plane. I doubt the transom flexing is causing the Chine Walk. You are trying to balance a vee. Take a 4 X4 and see if you can get it to balance on a corner. At some combination of speed, hull design, wetted area of hull, bow lift, engine trim, engine height, and a few not mentioned add up to start the back and forth tipping and fishtailing. Uncorrected it can often get severe enough to capsize the boat. Trimming in a bit and gently easing back the throttle, will often rein in the bonco. Mounting the engine higher on the transom is another option. Dual cable steering(probably already has it) adjusted to remove play/slop or Hydraulic steering may help too
If the transom is flexing, it usually means the wood under the fiberglass has rotted. It may last for a while, but it is a ticking time bomb waiting to detonate. It is repairable, just not cheap or fun to do.
Is it the transom, or are you just seeing the engine moving on the rubber engine mounts?

 

[Bisons1]

Did some measuring, the Hydraulic Jack is off center about 1/4 inch. looks like the transom might have a crack. There were two Talons on the boat prior to my purchasing the boat.. was in agreement that I would not use them for my type of fishing. So the owner kept them and knocked the cost of the talons off the buying price. the talon mounting bracket was attached the the transom, then the Hydraulic Jack plate was attached to that, then the motor. When I test ran it prior to buying, it was one whole unit. could setting the motor closer to the transom by 2 inches make much of a difference?

I can not raise the motor anymore then it is. It actually comes out of the water during turning. I have changed the weight distribution, noticed some difference. can get it to 60 with out it Chinning, but should still hit 70 easy enough. I ll take a closer look at the Transom issue..

 

[Chris1956]

Bison, (See post #3) You seem not to believe that different props (Yammy, OMC) can have vastly different performance affect on your boat. Different style props can and do affect boats differently.

 

[Bisons1]

I understand the different props, but i have know way of knowing what was on the Yammy. Where i am from, i dont have the ability to walk down to the local marine store and buy multiple props for testing.. I just dont see props as the whole issue.. yes it may have some affect on my top end and hole shots etc.. but 15 mph difference, i just dont see it.. but i am no expert, and its the reason i am on this site. So, i ll try some different props.

 

[Chris1956]

The Rake and the progressive pitch on a prop can make quite a difference in how well it holds the water during trimming, which directly affects handling and speed. Unfortunately, with the different prop designs, and different hull designs, it is hard to pick a winning design. That is why I suggested you try to reuse your old Yammy prop, since you had good performance with it,

 

[Bisons1]

Was doing some research through mercurymarine.com, was trying out their prop selector program. Says that I should go from my 2014 Evinrude 250 Etec 2 stroke, 23P prop. at 5800 wot at 63 mph. and Switch to a 14.625 x 27p 3 bladed tempest plus SS..and should get 5150 wot @ 70.64 mph. Going to see if i can test out a few props from my dealer...

on another note..
I have a 92 Champion 201 DCR, I run a 2008 Mercury 225 Optimax with a SS Temptest + 25 P prop, with performance vents. runs beautifully, not chinning, and hits about 64.5 mph at 6000 WoT... but I placed these specs in the mercurymarine.com and it says I should be running a 27-28 P SS prop, to max out my speed at 5450 RPM WoT, and attaining speeds of 81 mph.. does this sound accurate?