95 16" glastron setup help

[95glas]

hi i have a 95 glastron 16' bowrider with a 88hp johnson outboard.. - my issue is i have to run the motor adjustment all the way in and the trim all the way down ( currently has a hydrofoil which i want to remove- have had numerous people tell me they cost performance) in order to keep the bow down enough so doesn't porpoise ...this can't be right! tried a apollo s/s 13 1/4 x 17 prop- no noticeable improvement... would a jackplate help in my case or just make things worse? have had some one tell me on my boat i would lose performance, told a jackplate wouldn't help me ( they sell them- though gave me no reason why wouldn't help)
any way to elimitate as a possibility? measuring something perhaps?
need new control cables? just want to be sure this would help/ notice it as probably end up having to pay someone to install for starters..only other option i can think of is trim tabs...any other suggestions?

 

[NHGuy]

Re: 95 16" glastron setup help

There are many considerations when outfitting a boat for outboard operation. Your cavitation plate height is the thing to get after first. Once you have the hydrofoil off take a side view look along the bottom of the hull. You want the plane formed by the bottom of the hull to be followed by the cavitation plate above the prop. Later if you still aren't satisfied a jackplate can be used. Jackplates can be used to finely adjust the height of the propeller in the water to maximize your speed or control. They also benefit by getting the lower unit farther back from the boat. The water is less turbulent there, giving better bite for better propulsion. And the drive can be run even higher to further reduce drag. The really fast outboard guys have improved raw water pickups way down low on the lower gearcase because they run the drive so high the normal spot can suck air!
edit: Once you get to the point of raised jackplates and very high speeds you need to relearn driving the boat. Boats act very squirrelly when you get them way up past their designed hull speed. Hydrodynamics and aerodynamics start to take over. You get things like chine walk, and air can get under the hull, a very scary bad thing. I don't think your 88 will get you into that kind of trouble unless you are a really talented tuner. Check out the speed junkies at the scream and fly forum. They go real fast.

 

[steelespike]

Re: 95 16" glastron setup help

Has this boat had the stringers/floor/transom rebuilt?
If you put a 3 or 4 ft. straight along next to the keel from the transom forward
the bottom should be straight along the straight edge.no hollows or bulges causing the straight edge to rock.If there are any bulges in the bottom ahead of the transom it will cause porpoising.If the transom is too vertical, doesn't lean rearward
a little, you won't be able to trim in enough.

 

[95glas]

Re: 95 16" glastron setup help

trying out a different hydrofoil this week. looks like motor doesn't go in enough- was thinking of either transom spacers or jackplate to correct...also not sure but i think the motor is too high. any reason why u think i'd be told a jackplate would cost me performance on this boat?

 

[steelespike]

Re: 95 16" glastron setup help

Purpose of a jackplate is to get the motor in "cleaner" water and give easy
more precise height adjustment.I can't think how it would hurt performance. Don't know that it would solve trim in unless it adds clearance for trimming in.A foil is a bandaid covering a problem.At times they work well but can damage the motor,cause squirrly behavior.And almost without exception reduce top end.Tabs ,active or passive, are a much better choice.

 

[PWH1]

Re: 95 16" glastron setup help

I have a 16' Glastron outfitted with a 90 Johnson SPL. I recently changed to a 13.25 x 17 Solas prop with excellent results. That prop should work well with your application. I would lose the foil and give it another try...

My boat is a little rocket with the solas prop, jumping on plane in seconds and has gobs of low end torque. My WOT is around 5400 with a top speed of 42 MPH (GPS).

 

[95glas]

Re: 95 16" glastron setup help

tried with the apollo prop no foil...porpoises more. anyone know rpm that the 88 is supposed to be at?

 

[PWH1]

Re: 95 16" glastron setup help

RPM Range - 5000 - 5500

 

[95glas]

Re: 95 16" glastron setup help

thanks hopefully want to try again in next day or 2.. wasn't exact sure what my rpm was..i know with aluminum it reved less

 

[95glas]

Re: 95 16" glastron setup help

gotta go over my wiring the tach/ fuel gauge are giving erratic reading..actually only functional gauge i have is the trim..pilot tube broke ...always something!

 

[usskydvr]

Re: 95 16" glastron setup help

Just to ask the 'dumb' questions. You don't have, say, 3 or 4 6 gal gas tanks in the rear of your boat, do you? Also I'm a Merc guy, so I don't know if your engine may have the same setup, but Mercs have an adjustable tilt pin that can limit trim if not set correctly.

 

[95glas]

Re: 95 16" glastron setup help

just the factory gas tank thats built into the boat- has pin currently all the way in

 

[usskydvr]

Re: 95 16" glastron setup help

I tried. Any way you could post a pic of the transom/engine taken from the side at about cavitation plate level?

 

[TWIN_ZJ'S]

Re: 95 16" glastron setup help

Like USS says please post a side view pic of the boat and motor out of the water with the trim all the way down. It sounds like it may have been mounted wrong.

 

[79Merc80]

Re: 95 16" glastron setup help

I had the same boat and Smart Tabs did the trick. Before that I actually placed a big rock under the front seat to keep the bow down and eliminate the porposing. The Smart Tabs also eliminated the boats issue with steering in reverse. Here are a few pictures of the setup I had.

Hope this helps.

Craig

 

[95glas]

Re: 95 16" glastron setup help

I had the same boat and Smart Tabs did the trick. Before that I actually placed a big rock under the front seat to keep the bow down and eliminate the porposing. The Smart Tabs also eliminated the boats issue with steering in reverse. Here are a few pictures of the setup I had.

Hope this helps.

Craig

dam that is the same boat! just a heavier motor i believe? should be more prononced..had to ditch swim ladder? was thinking of tabs as well - but up to now couldn't get any feedback on them ..happen to know where can get replacement seat hardware for bow seats? dealer says unavailable

 

[95glas]

Re: 95 16" glastron setup help

side pic if any others needed please ask, thanks

 

[usskydvr]

Re: 95 16" glastron setup help

Can you take a pic looking straight across the back of the transom and down lower at the cav plate level with the engine set to steer straight ahead?
Is the skeg hitting the floor? it appears that you can't get the cav plate to be parallel with the bottom of the boat and that would cause a problam.

 

[79Merc80]

Re: 95 16" glastron setup help

95glas:

I'm not sure if that inline 6 was much heavier then yours is. Yes I ditched the ladder on the back after my parents bent it (Not sure how they did that). The tabs completely changed the way the boat performed (In a good way). Before the tabs, I was able to go 14MPH, if I increased the RPM's by 200, it would jump on the pad and go up to 33MPH, if I decreased the RPM's by 200, it would them come off the pad and back to 14MPH. With the Smart Tabsw, I was able to have control of how fast I went inbetween those speeds.

But, the BEST improvement of all was something they never claimed it would do. Before the tabs, I had very little steering control in reverse. It would start out fine, but within 10-20 feet, it would start turning (Either direction) and end up pivioting around the engine like the engine was nailed to a stationary place on the ater and the boat turned around that point. If I tried to correct it, the boat would travel sideways. With the Smart Tabs, I had complete steering control in reverse.

The tabs you see on that boat were actually wider than they needed to be, but it really did the trick.

As for replacement parts. I would try boat reacking yards, E-Bay, Craig's List. The plastic latches they used on the bow seats broke within the forst month on mine. I ended up putting hinges on them.

Craig

 

[95glas]

Re: 95 16" glastron setup help

thanks ... i think this is the route i am going to go..i think smart tabs even guarantees performance increase? just trying to decide composite over stainless? sent email to them - no response yet..part of problem imo is my boat is a bowrider and as of yet haven't use it as one. the jackplate i am thinking about would MAYBE help includes more tuck under but not crazy about adding more setback..longer cables, more pressure on transom,etc and with smart tabs can elimitate the hydrofoil i have less stress on lower unit, less drag, etc