Correct height on the jackplate?

[Theoutdoorsman]

My friend has a Stratos 201 Pro that he just installed a new HiJacker manual 6" jackplate on. The motor has been mounted and we are ready to water test. Can anyone confirm via this photo if we are in the ballpark for the initial test? Or, should the motor be lowered more? Better yet, where on the actual boat hull, should the cavitation plate line up? Many thanks!

 

[JB]

Re: Correct height on the jackplate?

With a 6" setback typical EV plate height tunes to 3-4" above the keel, BUT for any particular boat/engine/balance combo it is unique to that boat and has to be found by trial.

 

[Theoutdoorsman]

Re: Correct height on the jackplate?

So, you would suggest we lower the motor just a bit for the initial water test? Just trying to ballpark this thing prior to testing. Call us sissy's, but it's cold ....

 

[emdsapmgr]

Re: Correct height on the jackplate?

I'd agree-test it the way it is. You are probably not that far off. Keep in mind all you need to insure is that all 4 of the water inlet holes are covered when test running. This will occur soon as you float off the trailer. Take a buddy with you and have him drive, while you go back and watch the lower unit. When you start to get the boat up on plane-be vigilant. Watch the water flowing from under the transom. You only need to go a 150 feet to know. If you see a problem, (top water intake hole becomes exposed) immediately pull back on the throttle and idle back to the ramp, load it up and make your adjustment in the ramp parking lot. It's also possible you have it mounted too low. When planing you want the water flowing from under the transom to flow just under the anti-ventilation plate-just above the prop. If that plate is buried (water flowing over it), you'll get excessive drag, significant water spray. That's too low.

 

[Theoutdoorsman]

Re: Correct height on the jackplate?

Ok. Many thanks for the tips! Any last minute advice before heading out, such as what to do if the boat porpoises and what not? Also, in what increments should the adjustments be made. Sorry for all the questions, but we have no experience in setting up an outboard mounted on a jack plate.... ;-) ... BTW .... The boat is a Stratos 201 Pro w/200hp Evinrude (Renegade 13 1/2 X 25P four bladed prop). For those familiar with this setup, and just out of curiosity, what WOT speed should we expect to see?

 

[emdsapmgr]

Re: Correct height on the jackplate?

That's a good prop for that engine/boat combination. If your 200 engine has an "S" after the "200" in the model number, it's a high perf engine. XP/GT type. Probably makes about 220 hp at the prop. I'd think you would be in the 65 mph range, plus or minus.

 

[bob johnson]

Re: Correct height on the jackplate?

I have a 10" set back hydraulic jack on my boat and I found you don't gain near as much as some people suggest. I have seen it written on the bass boat forums where guys regularly use the jacks to tune their boats and they have posted that you gain about 1" of height for each 6" of setback you add...and my experience backs this up...now the boats hull has a LOT to do with it, and I don't know much about that hull....but...id say you might be a little high.....I am thinking you will blow out at some speed..below your top potential at the setting you are on...but since its adjustable...it is no big deal where you start!! does the owner have a base line rpm and speed, before the install to compare to?bob

 

[Theoutdoorsman]

Re: Correct height on the jackplate?

The owner says the boat does, in fact, have a tendency to porpoise ever so slightly at full trim and WOT. It is also a bit difficult to steer to the left. More so than before the jack plate installation. The boat has new steering cables. Any ideas with these concerns? Heading out in a few hours to water test again.

 

[kfa4303]

Re: Correct height on the jackplate?

It's not uncommon for boats to pull to starboard due to the rotational torque of the motor. As a result, while turning to starboard can be quite easy, it can make turning to port more difficult, especially at speed. There are a few things you can try. One is to get a zero feedback steering system which compensates for the pull to starboard and/or trim tabs which can be used to help the boat track true and should also help reduce/eliminate the porpoising at high speeds (LENCO is probably the best known brand). As stated before, trial and error will serve you best. It helps to write down performance numbers before/after a mod to what effect, if any it had. Just try not to get too OCD about it all. Once you start adding jack plates, trim tabs, etc... it's easy to get caught up in the numbers and forget about the fun of actually using the boat. Good luck.

 

[Theoutdoorsman]

Re: Correct height on the jackplate?

... it's easy to get caught up in the numbers and forget about the fun of actually using the boat.

If it were used primarily for pleasure boating, we wouldn't have even considered the jack plate. This boat is used as a tournament fishing rig, where performance is absolute. Unfortunately, 58 mph @5800 rpm WOT is where we sit currently. We were really hoping for 60 mph + .... :-/ .... We do plan to make some minor modifications to the height of the outboard in hopes of improving performance just a bit. As soon as this weather breaks, we'll make some minor adjustments, and give it another go. If anything comes to mind, feel free to voice your ideas. We're open to suggestions. Many thanks!

 

[emdsapmgr]

Re: Correct height on the jackplate?

Work on your setup. At 5800, that's not bad. This big bore looper will still make good hp up to 6000 rpm-it's max factory rpm range, so you have room to fiddle with your setup. I'd make sure you have the engine running as high on the transom as possible. Less lower unit in the water-the faster it will go. You can increase the engine height somewhat by filling in the top water intake hole on each side of the lower unit. It will cool just fine with only the 3 bottom holes. This will permit running the engine higher on the transom. Probably pick up a mile per hour each inch you go higher on the transom. When you get into this height area, best to consider adding a dash-mounted water pressure gauge to make sure it is being cooled properly at WOT. See this pic of a Johnson V6 lower that has been converted. Also, I'd consider going to composite reeds. They idle great, have great midrange and you may pickup 100-200 rpm's ontop.

 

[Theoutdoorsman]

Re: Correct height on the jackplate?

After much tinkering, we managed 60 mph at WOT (5800 rpm). We found the best all around outboard performance height to be approximately 3 1/2" off the transom. The rig steers much much easier now. The AV plate is "skimming" the waters surface at WOT, with water pressure holding steady at 22 psi. We have access to a 14 1/4 X 26P Raker prop. What performance gains/losses should we expect to see should we swap the two?

 

[emdsapmgr]

Re: Correct height on the jackplate?

That's what it's all about. Test and re-test to determine optimal setup. You may need another forward thrust hub. The hub is not interchangeable between the two props. (not a big deal, just be aware.) The raker is considered a "top-end" prop, even with the exhaust bleed holes for improved holeshot. You will probably see it's a little slower out of the hole than the 4 blade. Since it's only 3 blades, perhaps a little more efficient at WOT. Expect your rpm's to go down maybe 100-150 rpm's. Top end maybe a little higher. Both props are great bow-lifters. Both of them are high cup and high rake blades. They like to run high on the transom-they will both maintain bite if the top of the upper blade slightly pierces the water. Sounds as if your engine could be mounted one hole higher on the jackplate. You are getting to the point where you are tweaking your setup. Experimenting with engine height and props will yield maybe another 1-2 mph.

 

[Theoutdoorsman]

Re: Correct height on the jackplate?

Fortunately, we'd NOT made any changes to the setup for three consecutive trips. However, the boat has dropped from 58 to 50 mph at WOT. What we have found is low compression in two cylinders; numbers 3 and 6. Surprisingly, compression in both holes are dead even at 75 psi. Suggestions?

EDIT: I should also note that all other holes are approximately 90 psi.

 

[emdsapmgr]

Re: Correct height on the jackplate?

Powerhead compression issues become an issue when there is more than a 10% variance between cylinders. You're just beyond that point. Hopefully it's just a head gasket-that would be the easy fix. When you get the heads off you'll be able to get a good look at the cyl walls on #3 and #6.

 

[Theoutdoorsman]

Re: Correct height on the jackplate?

Assuming there is any light scaring on the walls, what then? Would you recommend honing and new ring kits for the suspect holes? 75 PSI seems, although low, not too terribly bad to me. It tells me the damage, if any, is minor. Your thoughts?

EDIT: We plan to pull the heads tomorrow for a visual inspection. Can you advise as to the correct torque specs, and sequence, for the head bolts? We're pretty certain it's a 90 model Johnson GT200. We'll get positive identification tomorrow on the year. Where can we locate a part number for the correct OEM service manual for the outboard?

 

[emdsapmgr]

Re: Correct height on the jackplate?

You can get an original factory manual from the original publisher, in Milwaukee. Check out this website: outboardbooks.com I wouldn't get too far ahead, thinking of scuffed cyl liners yet. Wait till the heads are off.

 

[Theoutdoorsman]

Re: Correct height on the jackplate?

OK. Now for the good, the bad, and the ugly. Here are the results of the head removal. First, here are the compression results prior to head removal: (head gaskets are in good shape)


Port Top > 90 Starboard Top > 90
Port Middle > 90 Starboard Middle > 60
Port Bottom > 70 Starboard Bottom > 89


Can these two holes possibly be honed and re-ringed, or are they subject to boring?
Opinions?

Photo's: (first two pics are "port bottom", last two pics are "starboard middle"):





PORT:













STARBOARD:

 

[bob johnson]

Re: Correct height on the jackplate?

looks like the bad cylinders all had extra carbon deposits on the piston domes....you might have had a rich condition in those carbs... MIGHT , its just a computer picture guess... doesnt look like you broke a ring yet...my thought...once you tear a motor down that far..... why risk returning and putting it together half baked.... for the cost of a piston and bore.....I wouldnt fool around with trying to hone and rering those bores

bob

 

[emdsapmgr]

Re: Correct height on the jackplate?

Most of the cyls may take a light hone, but the first pictured cyl may not clean up well. You can use some muratic acid to gently remove any alum that has transferred to the cast iron cyl liner. Then see what the liner wall looks like. You will need a new piston. 6 new ringsets. I'd be concerned about the reason for the scuffing. You might want to pull the carb apart that feeds that bad cyl (especially) and lay the jets on a table. Visually check them for any restriction. Likely that cyl was running lean (and hot) and carb problems are a likely culprit here.