Another HP rating thread

[reedjj]

I have a 2002 1756 G3 Center Console (the regular one NOT the Jet tunnel model) with a 40 hp prop Yamaha. Jumps on plane in 1 boat length and runs WOT at 31mph on GPS, and can run on plane at 15mph, it can run on plane in about 18 inches of water.... I would like to do a re-power while the current motor is still in good enough shape to sell and make a little $$$ off of. I do want to put a jet on it regardless of what the people around here say about it. Its rated for up to a 70hp. SusqyG3 has the same boat with a 90/65 jet which is still within the rated HP for the boat and would be more than enough HP for me. BUT!

My question is when I see boats like the blazers and allwelds with 150's and 250's on them I get to thinking... Why can't I go bigger? I looked at the Alweld 1756 JC (basic jet boat) its just a bare bones hull the same size as mine and its rated for 130hp?

Nevermind what the rating is for the boat or if its legal or not.... I am seriously thinking of putting a 115/80 Yamaha fourstroke Jet on my G3. the weight difference between the 90 and the 115 is only 11lbs and it's a 15hp gain.

If I do this I would be replacing the current factory center console with a fwd setup like the factory G3 jets come with and mounting both batteries under the console to offset the weight a little. that would leave only my fuel in the back. I currently run one 6gal tank and one 3gal tank. Without the batteries back there I could run two six gallon tanks (a 12 won't fit its too tall). I figure that either the 115hp or the 90hp fourstroke would get similar range and fuel consumption to my 40hp 2 stroke.

I would also be adding a jackplate to get the height set right.

Since no one on the east side of FL has a jet outboard I need help and suggestions from you guys here at tinboats. I really don't need the jet here in Northeast FL but the Gulf side and some of the rivers in central FL and southeast Ga are pretty shallow. Every time I have to slow down and trim the prop up in less than 1.5 feet of water I know I should have got a jet.

SusqyG3 please weigh in on this since you have the same rig. Since no one on the east side of FL has a jet outboard I need help and suggestions from you guys here at tinboats.

my boat can be seen here https://www.tinboats.net/forum/viewtopic.php?f=3&t=20508&hilit=2002+g3+1756+cc+dlx

Thanks
james

 

[Lil' Blue Rude]

I'd say the blazer and alweld are rated for the bigger motors because the transom are taller and dezined for the jets. Could be tellin you wrong but that's what I figure anyway.

 

[Johny25]

I am always on board for putting more HP on a boat but there is a point where you start to flirt with disaster. Your boat has a HP rating for propeller driven motors. So look at it this way, a typical 70 hp propeller drive weighs around 250-270 lbs and the Yamy 115 jet you are thinking about putting on your boat weighs 416 lbs. That is a significant increase in weight on the transom and you could be asking for problems. That is 145-165lbs more weight on the transom :shock:

Research I did shows the 90 jet coming in at 390 lbs and the 115 at 416 lbs. My guess is the 90 is pushing the limit already and the 115 may be the straw that breaks the camels back sorta speak?

 

[crazymanme2]

I'm a welder, fabricator by trade so its easy for me to talk but I would beef up the transom & put what you want to put on it & never look back.You can never have too much HP.
In beefing up the transom the corners are just as important as the rest of the transom if not more.

 

[Lennyg3]

I am always on board for putting more HP on a boat but there is a point where you start to flirt with disaster. Your boat has a HP rating for propeller driven motors. So look at it this way, a typical 70 hp propeller drive weighs around 250-270 lbs and the Yamy 115 jet you are thinking about putting on your boat weighs 416 lbs. That is a significant increase in weight on the transom and you could be asking for problems. That is 145-165lbs more weight on the transom :shock:

Research I did shows the 90 jet coming in at 390 lbs and the 115 at 416 lbs. My guess is the 90 is pushing the limit already and the 115 may be the straw that breaks the camels back sorta speak?

If you are concerned with weight, you can get a standard 115hp 2 stroke merc that weighs in at about 350lbs, and the 115 optimax comes in at 375. I'm sure that the 2 stroke yammy's are close weight wise. I don't imagine you plan on trolling with this boat, so why get the 4 stroke. It's heavier, slower, ect...

 

[susqyg3]

One thing I would consider is what type of water you will be using it in.. In rough conditions crabbing in the bay I have had water splash up over the transom, due to how much the boat squats.. Having said that though, I have a 21 gallon fuel tank and when I'm out on the bay I have the tank much more full.. My 90/65 pushes the boat great, and to be honest I don't know how much more I would get from a 115/80.. I get about 35 (gps) by myself with no current/wind.. I've had 4 people in it and gotten 32, and with 2 guys, boat blind, guns, decoys, etc, we got 33-34.. I can run on plane about 22, I forget the exact rpms.. In my opinion the 90/65 is plenty of motor for that hull.. If you were able to find a two stroke 115/80 it wouldn't be a bad idea.. You also want to figure out what the gas consumption would be, and if it will be enough of a tank for where you're running.. I don't know if the previous owner of my boat got a custom tank made, but it extends up under the rear deck a little bit. If you do decide to go bigger, I would build up the transom.. I wish mine was on a riser plate.. It seems sturdy and hasn't caused any issues, but coming off plane it always looks like the back of the boat is going under..

As far as the console placement, it can certainly help, but I don't think it would be necessary... I imagine most of the shallow water you're running is sand/gravel, and not the limestone boat eaters we have up here in PA.. You'll get more speed with a rear console, and more cavitation with a forward console.. Just a thought, but it may be alot of work for very little gain.. I don't know an exact depth that my boat runs at WOT, but I've taken it through some very shallow areas without an issue..

 

[reedjj]

Thanks guys.. I am always thinking of stuff to do to my boat. I don't think I will ever be done/satisfied with it. LOL thats part of the fun of it though.

I understand what you mean about the added weight on the transom with the 115hp fourstroke and even the 90hp four. At some pt the weight of the motor outweighs the benefit of the increased HP on a hull as small as mine. I had planned on adding the jackplate to get the height right but not really increasing the transom height to 25/27 inches like the Alwelds or blazers or strengthening it in any way for that matter.

Maybe just going with a 80 opti or the 90/65 yamaha is the best option. I sure would like to find a 2002 or newer 2 stroke yamaha 90hp with a jet unit for a good price.. I was looking at the specs online https://www.boats.net/outboard_motor/Yamaha/90HP/parts.html and the 2002 90hp 2 stroke yamaha and only weighs 261 lbs (prop version). The F70hp that my boat is rated for weighs in at 260 (prop version). That would keep everything with in weight limits and technically legal. Im guessing the 90 would pump out about 65hp or 70hp just like the fourstroke 90hp does!

SusqyG3, yours is a hefty 390lbs with the jet!

I really want to move the console fwd even if its not needed. Mainly just because I like the way it looks. But it would be expensive with new steering cable, and some of the added wiring that would need to be done, not to mention the console itself. I would also need to get a seat from G3 or get one fabricated.

 

[susqyg3]

Yup! I have plenty of weight in the rear.. My trolling motor batteries are up front.. I have 2 plastic battery boxes fastened to the floor right behind the deck to help with the weight a little, but there is still a cranking battery in the back... I love my four stroke though.. I know they have their disadvantages but it runs like a champ.. Starts up with a quick turn of the key even after sitting for a couple months.. The weight saving would be nice on a 2-stroke but oh well.. If you can find a 90/65 yamaha 2-stroke at a decent price I would definitely jump on it.. I can't imagine my boat with 150 pounds taken off the transom.. would be nice!

 

[Seth]

Most of these jet boats with those big engines are commercial certified so they don't have to abide by the horsepower limits. I'm not sure otherwise how they could legally put those big engines on boats like that. My buddy just got a 1956 blazer and it has a sticker saying it's a commercial boat. I know of other guys getting there boats commercial certified so they could put on a bigger engine that what the factory rated it for.

 

[Johny25]

Man I like that pic of your boat and motor Seth That thing looks like its kickin *** just sitting on the trailer =D>

 

[Seth]

Man I like that pic of your boat and motor Seth That thing looks like its kickin *** just sitting on the trailer =D>

Thanks! I kind of like it myself, but there are times I wish I had an 1856 or 1860 hull for the extra room. It's great for just two people though. I need to upgrade the troller to a 24v 70# model and add some decent electronics and I will be good to go. :mrgreen:

 

[River Rider]

Just to chime in on the the idea of beefing up the transom. I am in the process of doing the same thing. The motor weight isn't the only problem with going big, but the tourque on the hull itself with that much horse power. I have been running my 70 horse on my allweld for a couple months now and haven't had any issues with hitting rocks, but I have had some welds crack. The gussets in the back that attaches the top of the transom to the top of the gunnels keep cracking. Talked to a marine welder and found that it must be from the stress of the motor when turning and manuvering. To remedy I will be raising the transom up and then attaching to the gunells again basically like the true jets sleds. That I am told will strengthen the hull as well as raise it to keep the splash over effect when letting off the motor at higher speeds. But of course this is my 2 cents, and I hope to have photos of that progress soon on my thread to show the progress.