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Trimate II - Merc 2.5 175 - Comfortable Setup?

cbattles

cbattles

Member
I just rebuilt a LOT of my Trimate II.

New transom, floor, etc. I copied a lot of what I saw on here with the transom - ended up doing 3 sheets of 3/4" ply, put in some knees, etc. So, there's definitely some extra weight in the back compared to what would have been there originally.

Also, as of yet I haven't put anything back in the front besides the floor, so there's no seat, extra wood panels, or passengers to weigh the front end down.

I have a jackplate with 6" setback, the prop shaft as of now is about 2.5" below the centerline. I'm running a 24" Trophy+ on my Merc 2.5 175.

In terms of just raw performance, it's great. Trim all of the way in, if I get into the throttle, it'll stand the nose right up, jump out of the water onto plane, and just run.

Problems:

1. If the lake is anything but completely smooth, it's downright scary. At 40-45 mph plus, it's always about one decent ripple from hopping off of the water.

2. It doesn't like to plane off (or stay on plane) at lower speeds - I think this is because of how stern-heavy it is - it wants to either run fast or not at all. As soon as it's not going at least 30 mph, the stern just starts to set down in the water and the nose just starts to stand up (quite a bit) until you're back in the throttle.

If you put a tube/skier behind the boat and try to run at a reasonable speed (not overly fast), it doesn't take much to make it start (what I assume is) porpoising. In fact, it's difficult, but at certain throttle positions/speeds I can reproduce this without pulling anything.

Overall, it's just uncomfortable to run in and I'm really kind of scared to let anyone else drive it.

I've thought about some transom wedges, I think negative trim might help keep the stern up some and the nose down. I've also thought about just tossing some extra heavy stuff (like a couple sand bags) in the front or overbuilding whatever seating I put up there. I would really rather not resort to just weighing the boat down though. Any suggestions?
 
Your on the right track, go with the transom wedges, I've had them on 3 different boats that were all over powered and stern heavy, they work great, totally eliminates porpoising and you can stay on plane at a much lower speed, also faster out of the hole for water sports.

IMO no use carrying dead weight around up front, maybe if the wedges still didn't do enough you could move the battery up front but I think you'll be fine with just the wedges.

One example I have is I had a 15' stingray with a 150 Johnson and it would porpoise so bad that the only way we could pull a tube or skier was to have someone sit up on the deck at the very front, kind of dangerous I know, any way I put a set of negative trim wedges in and problem solved.
 
My lil ski mate (16'3") hull should be the same bottom as yours, just different top/interior. I run a 175 Evinrude, 4blade 24p (cupped) prop with transom wedges set back 4" prop shaft is sitting at 3.250" below the bottom of the boat. Low on fuel and 1 person on board run in the very low 70's. The transom wedges are necessary, this will take care of your planeing issues, ski/tubing and assist in rough water handling. I recommend dropping your prop shaft to 3 inches below the bottom of the boat. You should not be squirrely at 40/45mph, I'm thinking your bow is too high, the trophy plus assists in bow lifting, so the porpoising you’re experiencing is attributable to the lack of negative trim, and lowering the engine a bit should calm this down.
 
Thanks guys. I've got some wedges ordered up and I'm hoping to get them on by this weekend so I can go try her out.

Pretty short season here in Ohio but I'm really hoping to get this dialed in before the end of it.

Thanks for the feedback.
 
One other minor thing that may help with the proposing while pulling a tube is too hook to the back of the boat instead of a ski pole (if you are using one). It will change the angle of attack and settle the boat down. It will also improve your hole shot.
As far as the scary part if you haven't had a lot of seat time in it, it may take a little getting used to. Once you get her figgured out it will probably be a non issue unless there is something really wrong with the setup.
Just remember... if it doesn't scare you anymore ,it aint fast enough, and when it aint fast enough your gonna have to spend more money. :):):)
 
if it doesn't scare you anymore ,it aint fast enough, and when it aint fast enough your gonna have to spend more money.

You said a mouthfull there!!!:thumb:
 
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