Help with atypical motor setup

[thill]

If I recall, my Starcraft was rated for 140 HP.

 

[thill]

You are using a 50 HP as your main motor and a 25 as a kicker, right? I tried that years ago, and found that the big kicker motor didn't push the boat much faster than the 9.9 High Thrust Yamaha 4-stroke I ended up with. The 25 wouldn't plane the boat, and when I turned it up, it made a lot of noise and vibration and threw a lot of water around, but didn't make any speed. In fact, if I pushed the throttle too much, it cavitated badly and made LESS speed until I backed off. But that was a bigger boat, so maybe it will work better for you.

If I had it all to do over again, I would put either a 70 HP or a 3-cylinder 90 HP on the back with a 9.9 kicker next to it. But that is me. You have your own journey to explore. Maybe you will find a great combination in the 25 and 50.

Please let us know how it runs for you.

I also have a bolt-on ladder/platform, and I love mine just like Jethro. I got mine on Amazon for @ $120, if I recall.

 

[MrGiggles]

You are using a 50 HP as your main motor and a 25 as a kicker, right? I tried that years ago, and found that the big kicker motor didn't push the boat much faster than the 9.9 High Thrust Yamaha 4-stroke I ended up with. The 25 wouldn't plane the boat, and when I turned it up, it made a lot of noise and vibration and threw a lot of water around, but didn't make any speed. In fact, if I pushed the throttle too much, it cavitated badly and made LESS speed until I backed off. But that was a bigger boat, so maybe it will work better for you.

If I had it all to do over again, I would put either a 70 HP or a 3-cylinder 90 HP on the back with a 9.9 kicker next to it. But that is me. You have your own journey to explore. Maybe you will find a great combination in the 25 and 50.

Please let us know how it runs for you.

I also have a bolt-on ladder/platform, and I love mine just like Jethro. I got mine on Amazon for @ $120, if I recall.

That's my thinking as well. A 25hp isn't going to plane it so you are limited to displacement speed. The difference between a 25 and a 9.9 might be 1mph.

The good thing is that OP already owns the 25hp so it's certainly worth trying out before scrapping the idea.

 

[thill]

True. The 25 will work, it just won't be able to rev much. A big-diameter, low pitch prop may help it work better as a kicker.

I would try to sell or trade for a setup that will work better. Canada might be a different market, so it might not be so easy up there.

I just saw a 2003 Yamaha 90 on FB Marketplace for $2,950, and a Yamaha 9.9HT for $950 I wonder what he could sell his current motors for?

I wonder if that 50 will plane the boat? With the right prop and weight balance, it might. Might end up being perfect for what he wants and needs.

 

[PunkR0ckz]

Thanks for the replies guys.

Unfortunately, I will not go back to the "different outboard" discussion as it is pointless for me. I will say this however; The reason for which I bought the 25hp 4-stroke Mercury is because, as mentioned, there are some places that restricts me to a 4-stroke and 25hp is the maximum they will accept (or 40hp with a turbine) and originally, before finding this deal, I was planning on buying a 14' aluminum V-hull that was rated for 25hp as well. It would've been my "4-stroke dedicated boat", but things happened since I bought the 25hp and I can no longer buy the 14' V-hull for it. Therefore, I am stuck to putting it on this Starcraft Offshore hull for now, and only have 1 boat.

I've been sleep deprived for the last couple of days... and my mind's playing tricks with me... I'm starting to contemplate the idea of putting a sea-doo engine in the boat as I have access to a very cheap (100$CAD) 650cc sea-doo in working order. I believe that I could put the 25hp 4-stroke Mercury centered in the hull, on a manual jack plate, so that it clears the turbine of the sea-doo engine. Any ideas?

Yes, that sounds weird... but I'm exploring a lot of ideas. That specific 650cc Rotax engine was rated as a 70HP back in the days.

 

[thill]

That is an interesting idea. In the mountains not far from me, many guys will fabricate tunnels and use jet ski engines. They love them. That would certainly use some of that space under that giant splashwell area, and you can run shallow with one of those.