Outboard Upsizing - 50 > 70 or 90hp

[hvaldezz]

I'm about to make the jump from my Tohatsu 50D to a higher horsepower motor. Can anyone tell me for certain if the bolt pattern and controls are the same for Tohatsu, Suzuki, Yamaha, and Mercury?

I spoke with a motor rebuilder today and he thought they would be but wasn't 100 percent sure.

Maybe someone out there who's upgraded motors can let me know. One thing I worry about is if they aren't the same there would have to be some drilling done on the mounting. Also, my Tohatsu controls are on the pedestal and it looks like the controls used are for a left hand side attachment rather than a standard right hand control. To explain a little further, my other boat, a bass boat has a Mercury motor with a control box on the right side of the console (along the right side of the boat). The Mac 26X has the control on the right hand side of the pedestal, which is directly opposite.

Don't know if I make much sense but just trying to find the easiest fit for my needs.

Thanks for any help you can provide.

Henry

[Night Sailor]

Better ask a mechanic or dealer for the motor you intend to use. In general I think very much bigger heavier motors have slightly different bolt patterns. Maybe going from 50 to 60, 70 wouldn't but over a hundred would.

Every side mounted remote control unit I've seen has an option for being fitted on left or right side without any change of parts. It's just a matter of how they are bolted together. Again be specific with your intended parts change and ask someone who knows exactly what you want to accomplish. Dealer or manufacturer.

[Duane Dunn, Allegro]

I have a Tohatsu 50D that I am upgrading to a larger horsepower Tohatso TLDI. I'm told the 50D was the biggest motor made that had a upper set of clamps instead of bolts. It's mounting is not the standard most midsize motors use. This also means the lower bolts will not line up as well. I'm am expecting to have to seal up the two bolt holes I have, and drill 4 new ones for the new motor.

I'm also told we will have to check that there is not gap between the transom well and the transom itself inside. Apparently it was common on X's for there to be a void there that needs to be filled before mounting the motor. Todd at BWY who will be mounting the motor with me, says these are all easy things to adapt. X's also had the lip of the deck to deal with. He says the easiest solution is to all this is to 5200 up the old holes then put on a thin piece of starboard with lots of 5200. This seals and covers the old holes and builds out the transom so you do not have a problem with the lip when mounting the new motor. You can then drill clean new holes for the new motor.

It sounds like there is a good chance I will be able to use my previous control cables. The Tohastu control may also be usable but I think I'll switch to the new one as it is already with my motor. I guess it is functionally the same, the one change being that pushing in the key no longer is the choke, it is now the switch that changes the idle RPM.

The wiring harness between the motor and pedestal will have to be changed. I also have to change the tach as the new TLDI's have a bunch of new indicators not present in the older Tohatsu's tachs.

[Frank C]

FWIW, starboard isn't a good choice for any high-torque application. These plastics have a property called Flow. When subjected to high-torque, over time, the plastic will "squish-flow" away from the pressure point. That leaves the bolts & nuts slightly un-torqued. It's much better to use plywood or plate-aluminum to back and maintain high-torque applications.

[Richard O'Brien]

Hi Henry
This might help:
I've switched from Yamaha to Mercury, and briefly looked over Tohatsu. The Yamaha and mercury bolt holes are close, but not exact. I suspect the Yammy pattern was metric, and the Merc was US? Yes I had to do a little drilling and filling. No bad! surprised me since Yamaha makes some of the Mercs.

I never got to the Tohatsu bolt pattern because their controls are entirely different and will not work on any but their own.

The Ultraflex B184 works on the Yamaha, Mercury (with adapters) and others, but not on Tohatsu's. See Mods section under motor or cockpit, ultraflex.

[BKAFER1]

So if I change from a 50 to say a 70 hp
how much faster can I expect the boat to be?

[Rich Walton]

I went from a suzuki 50 to E-tch 75 speed went from 19mph and feeling sluggish to 24mph and the feeling of being on full plane

[ChrisP and Pam]

In my searching, I was talking to a dealer who was very helpful. And he had spec books. According to his books, he said that switching from a Yamaha 60 to a Yamaha 115, the top holes were identical but the bottom holes were off the centerline by 2mm more. A 4mm wider spacing is manageable. But even with the same manufacturer, there are differences.

[shehzad]

In my searching, I was talking to a dealer who was very helpful. And he had spec books. According to his books, he said that switching from a Yamaha 60 to a Yamaha 115, the top holes were identical but the bottom holes were off the centerline by 2mm more. A 4mm wider spacing is manageable. But even with the same manufacturer, there are differences.

I was also searching the same topic, if to go from Yamaha 50 to Yamaha 115.
If you menage to go for this change, I would be waiting for your final comments.
Would there be any issue of weight ?