Transom mod. Have you ever done it?

I would like to strengthen the transom on my bass boat and put a more powerful motor on it. It is a 1982 Glastron HPV165 with a rating of 120 hp. I currently run a Johnson 115. It does pretty good but I would like more power. Does anyone out there have any experience with this model of boat and can this be done? How to do it and wether I should do it? Thank you for any advice you can offer.

Re: Transom mod. Have you ever done it?

Hi maryhannaj, Welcome..... Im sure some have done it, but ppl do lots of things....just remember, the rated HP isnt just about the transom strength, it has to do with the hull shape too, being able to handle safely at higher speeds and disproportionate weight aft.

Aside from the engineering, it usually negates any insurance you may have......maybe not initially, but usually when something tragic happens and there is liability.....

thats just my 2 cents and im not saying you shouldnt do it

Re: Transom mod. Have you ever done it?

I posted a similar question a few days ago. There is a "formula" that the US Coast guard has and it is in this file. It was forwarded to me by Woodonglass and jbcurt00. Another boater and my self just plugged our figures into the formula and the answer was almost the correct figure given on our boats. The formula has to do with the length of the boat, the width of the boat and the height of the transom. Since I don't think you want to go to the trouble to lengthen or widen your boat, it would seem the only option left would be to increase the height of the transom....I am really not sure how one would go about doing that and/or what the outcome would be. Hopefully the link will work for you, if not let me know and I will see about redoing it. Good luck.

http://files.dnr.state.mn.us/education_safety/safety/boatwater/backyardboatbuilders.pdf

Re: Transom mod. Have you ever done it?

Google or YouTube search:

Chinewalk

before you overpower your boat

Some people deliberately push their hulls to chinewalk to test the limits of what their boat & their piloting skills are capable of. I've pushed almost every vehicle I've ever owned to it's throttle governor, on both 2 & 4 wheels. IMHO, it wasn't particularly smart, and neither is deliberately overpowering your boat or courting chinewalking. Happy to have survived my youth...

Re: Transom mod. Have you ever done it?

Thank you all very much for the advice, information and how to research this matter further. My thoughts were to add height to the transom and build some kind of stringers spaced evenly from side to side from the heightened transom to a second transom forward, directly in front of the forward edge of the splashwell, basically cutting the bilge compartment in half and into its own independent compartment. Just a thought for a winter project. Although this idea doesn't solve the problem of length or liability. I can picture it but it doesn't mean it will work. Any further thoughts?

Re: Transom mod. Have you ever done it?

Since your boat is an '82 it does have potential for water intrusion and saturated foam which could be slowing it down if you haven't already checked for that.

I also say nay to a bigger motor, but there are things you can do to your boat and motor to increase their performance. Like making sure your hull is light and dry, precision tuning your engine, and making sure you have the correct prop size... all of the can make a considerable difference.

Re: Transom mod. Have you ever done it?

Adding tilt/trim can be equally benefitial too

Re: Transom mod. Have you ever done it?

Tilt trim and put on a jack plate, start tweaking.. Most boat motors don't ride at the perfect level for high speed. Basic formula is the cavitation plate in line with the bottom of the hull, works for most but it can give up a lot of potential if your looking for it. With T&T and a jack plate, you can tweak your motor height, and probably get more out of it. It's why many of the outboard go-fast boats run jack plates.

Re: Transom mod. Have you ever done it?

Thanks for the link. It works perfectly. And I will just say again thank you to everyone for the advice. I will also say that the motor has tilt and trim, the cav plate sits about 3/4 inch above the lowest point of the transom, its propped with stainless 3 blade 12 3/4 dia. 21 pitch, no jack plate, compression between 108 and 115 on all 4 running at about 43 mph GPS at 5500 rpm at 4750 ft elevation. As far as wet foam. A definate possibility. I need to get that figured out for sure. If there are any upgrades that can be done to that particular motor without damaging it, that would be great to hear some input on. I am new to outboards but I know my way around a motor, tool box and manual. Unfortunatly, I don't know my way around a yacht club if you know what I mean. This boat is in pretty darn good shape on the outside for its age so I am hoping that I find it dry inside when I dig into it this winter. Once again thanks for all of the advice and the welcome!

Re: Transom mod. Have you ever done it?

maryhannaj said:

If there are any upgrades that can be done to that particular motor without damaging it, that would be great to hear some input on. I am new to outboards but I know my way around a motor, tool box and manual.

Click to expand...

Might read thru the Johnson OB forum or post an OB performance thread there:
Johnson & Evinrude Outboards

They'll likely want as much info as possible:
4cyl 1982 (?) Johnson 115 OB model XZY76

propped with stainless 3 blade 12 3/4 dia. 21 pitch, no jack plate, compression between 108 and 115 on all 4 running at about 43 mph GPS at 5500 rpm at 4750 ft elevation.

Click to expand...

Post up some pix of what you're working on over this way, unless there's a problem, the OB forum won't be as pix dependant

Re: Transom mod. Have you ever done it?

I have posted here before and was tring to get more pics put up but I had a bit of a smartphone issue, and had to re-register under a different username. I tried to use the old one but it didn't work out. My old one was jwjw7108. No big deal to me, I just hope the forums are ok with it. So here's another shot at the pics I have on hand for now

Re: Transom mod. Have you ever done it?

I have no idea why the pic thing is working the way I think it should but that is what I have. It's not bad. The deck has been modified and extended. That's my boy with his wiper. He's pretty happy about it. I know that's a bit off subject but the boat seems to me to have the same type of hull design as a Bullet bass boat I watched on youtube. It had a big Merc on it and that thing was crazy fast. Great looking boat too. I dont know what that thats boat dimensions were but I do know that my boat has a 6'9 inch beam at 16ft 2 inches length and is 33 inches at its deepest point. If anyone runs a boat with similar dimensions, please let me know how you are set up and what you are running. Thanks everyone!!