Mercury 150HP on my boat?

[scottrbishop]

I have a chance to get a great deal on a 1983 150HP Mercury Engine w/ Tilt & Trim. The boat in question is a 1973 16 foot Glastron GT-150 that currently runs an 85HP Mercury. The boat only gets up to about 33mph with a single person in the boat with calm waves. Add the weight of a few passengers or a skiier and that top speed goes down considerably. You constantly feel like you want to go about 5-10 mph faster while slaloming. I know tthat 85 to 150 is a big jump in power, and I'd rather find a 135 or so. My question is, what are the consequences of such a big upgrade? I know bond ran his GT-150 with a 135 evinrude on it, and I've read of people putting 150s on their GTs. What type of problems am I setting myself up for?

Thanks,
Scott

 

[SpinnerBait_Nut]

Re: Mercury 150HP on my boat?

First, is your boat rated for a 150?
Check the CG plate and see.

 

[scottrbishop]

Re: Mercury 150HP on my boat?

The plate on my boat is long gone, but it was only rated for 90HP back in 1973.

Here's a picture and some details
http://www.classicglastron.com/bondposter.htm


I know a lot of people hang large motors on them, I just want to know what I might be getting myself in to.

Thanks,
Scott

 

[SpinnerBait_Nut]

Re: Mercury 150HP on my boat?

Ok, someone will chime in I'm sure.

 

[JB]

Re: Mercury 150HP on my boat?

Don't put over 90HP on it, Scott, and then only after confirming that the transom is sound.

We all know or have heard about people who have done stupid things and some of them even surviving it, but the risk/reward analysis says it is not worth the risk. . . not by a long shot.

 

[steelespike]

Re: Mercury 150HP on my boat?

I have a chance to get a great deal on a 1983 150HP Mercury Engine w/ Tilt & Trim. The boat in question is a 1973 16 foot Glastron GT-150 that currently runs an 85HP Mercury. The boat only gets up to about 33mph with a single person in the boat with calm waves. Add the weight of a few passengers or a skiier and that top speed goes down considerably. You constantly feel like you want to go about 5-10 mph faster while slaloming. I know tthat 85 to 150 is a big jump in power, and I'd rather find a 135 or so. My question is, what are the consequences of such a big upgrade? I know bond ran his GT-150 with a 135 evinrude on it, and I've read of people putting 150s on their GTs. What type of problems am I setting myself up for?

Thanks,
Scott

Ok, I'm not familar with Glastron models but will assume we are dealing with a 15ft boat and probably a sporty one.Tell us the WOT(wide open throttle) rpm and speed.It would seem that a sound properly setup 85 would be closer to 40+mph.And propped correctly would pull a skier pretty easily.I've seen a 90hp Evinrude routinely push a 1400lb 17ft boat to 40+mph.Give the motor a compression check,be sure throttle is opening all the way.fine tune the setup.Especially the verticle height.Verticle height alone could add 2 or 3 mph.,depending on where your at now.Stay away from the 150.

 

[Silvertip]

Re: Mercury 150HP on my boat?

If you do hang the 150 on it, make darn sure you don't tell your insurance guy. And if someone does get hurt or you have an on-water incident (your fault or not) I hope you have deep pockets as someone else will own all your stuff.

 

[deejaycee_2000]

Re: Mercury 150HP on my boat?

150 should be fine, I have a 200hp yamaha on a 16ft raven speed boat .....

 

[tashasdaddy]

Re: Mercury 150HP on my boat?

i have scrapped several of those where they were over powered. one had a 1350 merc on it, that i had to remove before towing home. bought it for the motor.

 

[Dhadley]

Re: Mercury 150HP on my boat?

The GT150 is a 15' boat. I had a 125 on mine (back in the day) and those in the movie had 135's on them. HOWEVER, the transoms were beefed up. A lot. Especially the one that did the jumps. (Yes, it took more than one try to get the shot. A lot more)

 

[SpinnerBait_Nut]

Re: Mercury 150HP on my boat?

Have to concur with Silvertip.
Rated for a 90 and you want a 150 on it?
Asking for more problems than just if the transome will hold it, IMHO.

 

[guy74]

Re: Mercury 150HP on my boat?

Scott,
I now run an over powered boat, I hung a 100hp motor on my boat that is rated for 85hp. When I rebuilt the floor and stringer I beefed up the rearend of the boat by tying the stringers, floor, transom, and splashwell together with tall verticle stringers all the way to the front of the rear cover. Probably made it into the strongest made v156 around, but that doesn't fix the rating problem. The main problem with going over the rating is that I now have a boat that was designed to go 40mph that runs over 55mph, it doesn't handle well at that speed. I had no problems with my insurance company, I was upfront with them and my agent signed off on it. He said that he saw no difference in that, and people that put larger motors into cars that weren't designed for them. If you over power your boat, be careful, it opens you up to alot of risk. I didn't put on the bigger motor to go faster, just to pull up skiiers easier. I now will not let others operate the boat though. I also don't plan on operating it this way for very long, just until I can find a bargin on a bigger boat to hang the 100hp motor on. I see overpowered boats around here all the time, and I have never heard of it causing a problem. There is a 1982 Glastron GX 150 here with a 150hp Evinrude on it, it's been around for years, but I'm not sure I would ever go that far on overpowering a boat though. I think you should give it alot of thought, and check for other options before you take that step.
Sincerely,
Brian

 

[scottrbishop]

Re: Mercury 150HP on my boat?

Thanks for the responses all. I am very conflicted. I could get this motor for practically free (after selling my old one), but then I'm left with the task of reinforcing the transom and possibly replacing my current problems with a new set of them. Everybody says I should be getting more power out of a 85HP motor but it's had a fresh tune up, and a new 19 pitch prop. The motor looks like it hasn't changed position since the factory installed it 35 years ago.


But what's a free motor if it'll force me to spend a grand configuring it, mounting it, tweaking it, etc.


I feel like I'm going to need a new motor one way or another, because once a few people get into that boat, slalom skiing is not an option.

 

[scottrbishop]

Re: Mercury 150HP on my boat?

Maybe I'll see how low this guy will go on the price, with the full intention of walking away unless it's a steal. If he doesn't sell it to me he has to take a 250 mile road trip up north to put it in storage.

 

[scottrbishop]

Re: Mercury 150HP on my boat?

For the crew who are against over-powering for the sake of legallity...

If I were to get into an accident with this boat with a 100HP engine (as opposed to a 150), wouldn't I be in the same amount of trouble since it's only rated for 90hp? It seems to me that half the gt's I see are over 90 hp.

 

[Solittle]

Re: Mercury 150HP on my boat?

Lawayers would love to represent the plaintiff if you have an accident even if your insurance company dosen't object. You're call - - you're risk - - you're stuff.

 

[Scaaty]

Re: Mercury 150HP on my boat?

Stuff the motor on. I raced OB's in the 70's in 16/17 footers.
EVERY GT I saw had a 150 Merc on it..came stock with the 90's. The 70's..that was the time they (INS)...were ending the the Muscle Car..high HP ..a no-no..might hurt ouselves.....
Boats built like a freaking BRICK!..(just ice pick the transom..lousy storage will have a soaked hull/transom connection somewhere)....and if ya find a "SIDEWINDER"..,16 ft..(rated 90hp too..we all stuff 150's on'em..(lousy goofy colors in Metalflake..go for BIG bucks..solid boat..like The GT..
PT+T on the wheel..foot throttle REALLY worth it..get that puppy up to 60/65 plus mph...watch the hull start flying....ya will wonder why ya think women are that good after all..FREAKING RUSH!!
That figured, ...do a 2 blade SS Prop, 13/14 ..figure 26/28 pitch..cupped..slow hole shot, but when it comes up on plane..feather the throttle...it will ventilate 'till it grabs..(you only..passengers might have to do a "Hands up" on the bow 'till planeing..then HOLD ON!
Had a 150XS on a 17 footer in the 70's...14x28 Surface prop..did 73mph..a GT with a stock 76 150, ..most lower unit in the water..slowly went by me. ROCK SOLID...while I was doing a little "sawing" at the wheel to keep chine walk at bay..
Don't let the old farts scare ya..GO FOR IT!!!!!!!!!!!!!
I just put together a "Crank up rebuild..".Merc last winter..70's 135 SS..16 foot FlatBottom..12 inch flat chine..deck same hight......12 inch "Pad"..SSprop..12x26 cup...(GOD, the rush of hitting 4000rpm...prop bites..gone!!!!!!!!!!!........jumps....God...llke an old SK boat drag boat!...Jet sleds with punks..HA!..blown off Accel..or WFO..still got then grin from summer.....

Both sides 1 inch drop at the chines.."Air Ehancement"..boat 350#'s, motor 300#'s..my fat butt 200+..next Bday is 58...
NEVER growup...not worth it..!!!!!!
PS...click my name ..search recent posts..there's pix of my old Switzer at speed.., and my new built Flatty..think in "10 best good looking small outboards"..(I kinda fudged..what was big then, is SMALL now..!..and I still have TWO old 3hp "Weedless" old Johhnys..one adapted to a straight
shaft..later L/U... and one Belgium Rude..pristine..and more ..been at it 50 years....(then theres the 6 bikes..3 old pristene Harleys..then the "sportbikes"...with triple HP of any HD!..............Rock on..go fer it...ya only have one "envelope" in life..look fer the edge!..if not, yer taking up space..!!!!!!!!!..

 

[SpinnerBait_Nut]

Re: Mercury 150HP on my boat?

For the crew who are against over-powering for the sake of legallity...

If I were to get into an accident with this boat with a 100HP engine (as opposed to a 150), wouldn't I be in the same amount of trouble since it's only rated for 90hp? It seems to me that half the gt's I see are over 90 hp.

Yep and I don't care what your insurance company says, it's what the Government(Coast Guard) says that makes a difference.
Have an accident with the oversize engine on and watch how fast the insurance company does a 2 step.
Don't care what anyone says, they just have not had one to find out.

Had a pal that has just about lost everything because of it.
He fished tourneys a lot and was restricted to 150HP in these.
He had a 200 so he put a 150 cover on and fished them for 2 years, n/p.
One he was in and a non tourney fisherman was coming out of a cove and came out in front of pal.
He hit him broad side and now that man can not use his limbs from the waist down.
His insurance company sued the pants off my pal and the investigation showed he was running the wrong cover on his engine and he should have not been in the tourney.

So be very careful. The insurance companies will tell you anything to sell a policy.

 

[rndn]

Re: Mercury 150HP on my boat?

Maybe you'll come to the right conclusion and decide the boat and motor package do not work for your needs. Look around for a boat setup that will work for your needs.

 

[Frank Acampora]

Re: Mercury 150HP on my boat?

Scott: The boat in my avatar is a 153 or 156--I forget the numbers. Glastron 15 foot deep vee--15 foot 9 inches long. It has a 90 on it and does 42 with just myself and 12 gallons of fuel. in the avatar it is going 36 or 38 with 3 people. So: I think you are just not getting the proper performance out of your 85.

You will have several problems with the Merc 150 -- The GT150 is relatively narrow and low in the rear so:
1. The added weight of the engine will make it ship water over the transom when you slow down rapidly
2. skiers will need to re-enter the boat over the side, not the rear, so as to not swamp it.
3. Feeding the beast! You can only fit so much gas in that boat and you will be surprised at how thirsty a 150 can be while skiing.
4. Rub rail is only screwed into the wood backer--not bolted, so you may start to loosen the rub rail and compromise the connection holding the deck to the hull.


But if you like speed, It sure will be fun.

NOW. One of my boats is a 14 foot flat bottom rated for about 35 HP. I have a 90 on it and it does 55-56 MPH. I just bought a cleaver prop and I am going to try to get it to 60 MPH. At that speed, it will not turn. Straight is the only option. I do not run that boat when there is appreciable boat traffic, and I always WEAR my PFD any time the boat is moving. AND--I have connected a deadmans switch. Yes! In the past I have flipped boats. Some of us old farts have fun in the air.

BTW: I have gone into the water off a slalom ski at about 60. Ripped the vest and, let me tell you, that's not an experience I want to repeat. Not even time to say, "Oh, S**T!" It's like UH! Oh, take me home.

I built up the transom 5 inches higher and specially re-enforced it. It is rock solid and I could probably hang a 250 on it with no problems. The hull also has special all fiberglass stringers and the deck is fiberglassed to the hull. After running a while I needed to install extra cross members--the floor would flex up 1-2 inches while running over wind ripples. See? It's not just the transom you need to worry about.

However I carry 9 gallons of fuel and that runs me about one to two hours. I drive the boat for 2 hours. Then I take it home and re-glue it for 8 hours. It was never designed for that amount of horsepower and eventually, something gives. I accept that as part of the cost of running that boat.

You may find that you will need to re-floor and re-stringer your Glastron. Then again, you may not--won't know until you do it.

If you want to see how I re-enforced the transom, go to The Chrysler Crew, join, go to photo albums and look for Frank's boats. It won't cost much to do the transom properly--couple of pieces of .080 aluminum--aircraft grade, NOT diamond plate, and a couple of dozen SS screws in various lengths. Way less than 100 bucks.