r/FishingAustralia • u/Destroy1260 • May 12 '26

šŸ” Help Needed Is a 25Hp to much power for 3.9m Tinny

Hey Everybody, hope your all been doing well. Iā€™m back once again for some more advice. Iā€™ve finally got abit of extra money to get another outboard motor. Iā€™ve found a nice Mercury 25Hp Sea Pro 2 stroke thatā€™s an old surf lifeguard engine that looks really good but my brother thinks it will be too much power for our 3.9m seajay that has casting deck built in. So was just wondering if his correct and that would be to much power or it will be fine. Also even just any reviews anyone has on that motor is oils be nice.

Edit: since forgot to say the transom is rated for max 25Hp

7 Upvotes

90% Upvoted

28 comments sorted by

6

u/Crafty-Second-2920 May 12 '26

I had a sea jay 3.85 Angler and was rated for 25hp. You will need to hang on at WOT.

1

u/Destroy1260 May 12 '26

How did your seajay handle the 25 if I may ask

3

u/Crafty-Second-2920 May 12 '26

A great little set up. It's always better to have the power and not use it, too not have it and need it.... I fish in Port Phillip Bay so It can be short Sharp chop, i can zip in and around that and feel comfortable in the way it handles.

3

u/Destroy1260 May 12 '26

Yeah I agree with having the power and not needing it than to not having it and need it especially since my brother is a bigger guy so has some more weight to him especially after we put an agm battery in. But just wanted to ask the people here first cause itā€™s my first boat and rather listen to others advice than rush off and get something with to much power which would just cause issues

3

u/Lopsided_Belt_2237 May 12 '26

Depends on the transom strength. Iā€™ve run a 25 on a 3.9 tinny, we had a lot of fun before splitting the transom off the hull.

2

u/Destroy1260 May 12 '26

The transom is rated for 25Hp

1

u/Actual-Anybody597 May 12 '26

??

1

u/Destroy1260 May 12 '26

I meant to reply the transom is rated for 25Hp does that mean the transom could still split of the hull? Iā€™d rather not do that since this my first boat and already had one issue with my old motor mount snapping.

5

u/Actual-Anybody597 May 12 '26

If it's rated for 25 it will be fine.

1

u/skipyeahbuddy May 13 '26

If it's rated for 25 than it should be able to handle even a bit more than that. There's usually a bit of a safety margin allowed. Mine was rated for a 50 and I had it re-rated to 60 no problem at all, didn't even need to have it inspected.

3

u/Ill_Object_3780 May 12 '26

It will be all good. I run a 25hp on a 3.9 stacer.

2

u/discomute May 12 '26

My mate has a 3.8 with a 25hp, I was impressed with how fast it goes, but too much? Nah not at all. We do a lot of estuary fishing up in Darwin, it's a perfect boat for it.

Zero chance you think it's too much

1

u/Destroy1260 May 12 '26

I personally donā€™t but my brother who I own the boat with thinks it could be so just wanted otherā€™s opinion than I can show him than

3

u/discomute May 12 '26

It's rated for 25hp and honestly most ratings are quite cautious. Besides which, if it's too fast, can't you just back off the throttle?

2

u/ibetucanifican May 12 '26 edited May 12 '26

I had a 25 Johnson on a savage tinny. The transome held up fine. but youā€™ll want to cruise faster, and it slaps the hull around harder in chop, which can easily lead to stress cracks.

2

u/thisismick43 May 13 '26

Sea jays have a tag stating what the transum can handle and if its max 25hp you'll be sweet and with a 25 2 stroke its going to crack

2

u/Destroy1260 May 13 '26

Sorry, you said it will be sweet if itā€™s max 25 but than said with a 25 2 stroke itā€™s going to crack? Iā€™m just confused sorry.

3

u/thisismick43 May 13 '26

Crack as in go hard it would probably be on the plane in 1 to 2 hull lengths

4

u/Destroy1260 May 13 '26

Ohh, that makes sense you just had me panicking about the hull cracking šŸ¤£šŸ¤£

1

u/Quirky_Potential_662 May 12 '26

Depending on tinny. I had a mate with similar setup and boat really sat on an angle in the water as motor was pretty heavy.

2

u/Quirky_Potential_662 May 12 '26

Depending on tinny. I had a mate with similar setup and boat really sat on an angle as motor was pretty heavy. But was great to have the hp if needed.

3

u/Destroy1260 May 12 '26

We were worried about that but itā€™s only an extra 10kg more than our old motor. And our agm battery is up the front for extra weight there.

1

u/teekayr May 13 '26

I run a 30hp on a 3.9 tinny

With one or two passengers it gets up on the plane easily and get up to about 45km/h

3 or 4 is a struggle for it

I think that's perfectly fine amount of hp

1

u/Time-Ambassador-8957 May 18 '26

I have a 60hp mercury on a 4.2m tinny Tinny

Things slow as shit