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scottskis
04-27-2009, 12:43 PM
1st post – great site! I’m loving all of the tower of power stuff!
I should state 1st that I have owned this boat and engine for 19 years and that it is used for skiing, tubing and cruising around.
I need to keep a set up that allows for that reality as well as the fact that my kids are now old enough and may be taking it out on their own this year.
So it has to have SAFE, predictable handling.
Also, I am a divorced dad with one in college and we have other expensive hobbies like skiing and motorcycles, so keeping down the costs and spending money wisely are critical – I cannot afford experiments that don’t work!
My questions are about repairing and/or making some changes to my steering.
The boat:
1971 Glastron GT160
1971 Merc 1150
19p SS thru hub exhaust prop (no name, nothing special, has some dings)
Cavitation plate is about ½” above the bottom of the V.
Stock splash well steering system
Teleflex NFB steering system
The problem:
1) The splash well steering plate after 38 years has rusted out.
2) The boat generally runs, planes and handles well, but it porpoises at what seems like very low trim angles (I do not have a trim gauge).
The motor has been re-ringed and has had some new bearings, but that was 10 years ago and it is a little tired, but the boat still runs mid to upper 40’s.
The bottom of the boat is very flat on the starboard side and 1/8” or less of a depression (hook) on the port starting 2’ or more forward of the transom.
Maybe 10 years ago I replaced the transom and tied that all in to the stringers. I should have taken the top off of the boat and completely replaced all the wood, but trust me the transom and stringer systems are very, very solid.
The work I did also allowed me to place an eighteen gallon fuel tank in the hole and created a bench seat under which I place the battery and the trim pump (the boat did not come with power trim originally and I was tired of carrying extra fuel tanks on the floor). This is the only way I could hold 18 gallons of fuel and still have a place for the battery and trim pump. The keel at that time was in perfect shape so I did not do anything with it.
So now that I have the fuel tank, battery and pump out, I see where the hull delaminated from the keel and believe this to be responsible for the hook on the port side and have plans to reinforce and repair it.
While the boat generally did not porpoise before repairing the transom and stringers, I have checked many times and I did not introduced a rocker, but I did move the CG rearward by adding the equivalent of about 3/4 sheet of marine plywood (3/4”) and disposing of all the wood trim used in the interior as well as rotted flooring and water logged foam.
Even with a couple of good size guys up front, it will still porpoise, so I do not believe moving weight forward is the answer.
So, back to the steering which is what is preventing me from using the boat.
I see my choices as;
1) Buy a new splash well plate for $130
2) Move the steering to the tilt tube. This will require drilling a clearance hole and booting it somehow on the port side of the splash well as it is too narrow for the steering to clear.
3) Buy a 6” transom jack. 2 piece = $135 plus shipping, 1 piece with on water adjustment = $185 plus shipping.
Advantages/disadvantages;
1) Simple one for one replacement, known handling outcome.
2) Lowest cost option and safer steering, known handling outcome, but I’m not sure I like the splash well mod required.
3) Sexiest option, most expensive option and the most work, but may eliminate the porpoising. It may add some speed (especially if I change props – 22-24” chopper?), I already own a longer steering cable, but it would either have to come out a hole in the transom (sealed of course, but the idea worries me), or out the top deck or side – not as pretty of an option as on a sidewinder or other boats because of the “ducks ass” turn up at the rear of the deck.
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So what do you guys think?
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scottskis
04-28-2009, 08:09 AM
Ok, sorry if my post was too rambling or too much info. Let me break it down;
Should I put a jack plate on my GT160?
If so, how should I run the steering cable out of the hull?
If not, should I replace the splash well steering plate or make a hole in the splash well to accommodate the steering arm?
Extra points if you have a detailed picture of a clamp mounted inline Merc on a jack plate!
Thanks,
Scott

oldskier
04-28-2009, 09:30 AM
Scott, I guess we are a little confused, sounds like you are trying to fix porpoising with a steering change? Shouldn't affect porpoising. The jack plate will require the engine to have a little more setback, which I understand will increase the porpoising problem. I would concentrate on getting the hook out, but owning a Viper I am an expert at porpoising, not figuring out how to avoid it. Mine got way worse when I put a plate on it and raised the engine up. It had very little porpoising with the prop 4 inches under the pad and the motor bolted to the transom.

scottskis
04-28-2009, 10:37 AM
Thanks for the reply O.S.,

Sorry if my post(s) are confusing!

Yes, I will fix the hook and hope that it helps with the porpoising, but I don't believe hooks to generally cause it - rockers generally do right?

Yes, I know that a jack plate on some boats does lead to porpoising, but I was thinking that if I move the CG further back with a jack plate that it (the CG) would stop getting ahead of the center of lift and therefore would stop the porpoising or at least allow the hull to free up more before the onset of porpoising.

Ok so that is one conversation, now forget it for a minute and assume the hull is handling fine.

The 2nd conversation is that I need to rig the steering and have the 3 options listed above.
Which makes the most sense for my type of boat, use and budget?

thanks,
Scott

oldskier
04-28-2009, 12:22 PM
I always try to choose the simplest option, if the steering plate is available, I'd put one on it. My best friend since I was 4 yrs old owns the same GT160 we skied with when I was 16 (1971) and the rig works best with the original setup. Never had a porpoising problem and I'm still confused as to what made yours start if it isn't the hook in the bottom. I've driven it for hundreds of slalom runs and it never had a porpoise problem. Just don't know hydrodynamics well enough to diagnose your problem.

Good luck, Bernie