Top Speed and Trolling with a 20hp 4-stroke on a 12' SIB?

Slayer33 · 14 March 2017, 22:23

I have a Nissan 9.8 2-stroke right now, great motor, but it stinks... literally when trolling..

I'm looking to upgrade my 2-stroke to a 4-stroke 20hp Merc.

Does anyone have this motor or a 20hp 4-stroke on a 12' SIB? I am wondering if it'll troll slow enough with 2 ppl in the boat w/gear...

The 9.8 was ok, it was hard to dial in a decent speed and it wasn't a pleasant experience compared to the 5hp 4-stroke I had previously.

I am wanting more top end speed to get me where I want to fish and to be able to troll... I can get a good deal on a 20hp Mercury 4-stroke here so I am trying to decide if its worth the $$...

I topped out at 15mph with my Nissan 9.8 with me and my fishing buddy last year, 17mph solo. What kind of top end speed can I get with a 20hp 4-stroke?

nicksharpe · 14 March 2017, 22:52

I have a 3.8 SIB with a 20hp 4 stroke Mariner. I've only had it about a month and it goes pretty quick. I'm told about 22mph.

Your problem might be trolling. Even at tick over I'd say it goes 2mph, so you might be on and off the throttle too much.

Get the 20hp and an electric motor for the trolling?

Fenlander · 14 March 2017, 22:53

Very similar thoughts to Nick above re speeds...

My 20hp Suzuki 4-stroke (2016 fuel injection model) idles at 850rpm and with its 10" prop idle trolling speed is 2.14mph. It will go all day like this in near silence and smoke free obviously. The Mariner should be broadly the same but has to be said the Suzuki with ECU controlled EFI has an advantage in that the idle/trolling is controlled by the ECU at that figure with no variation for hot/cold engine or load (within reason).

I'd guess top speed for a 20hp on your SIB would be around 23mph.

chipko · 14 March 2017, 23:02

I had both a 9.8 Tohatsu 2-stroke and a Suzuki DF20A 4-stroke on 3.5/3.8m sibs. Not into fishing so no requirement for long term trolling.
However the Suzuki would happily tickover all day long in gear if required. The Tohatsu being 2-stroke would soon foul up the plugs if left on tickover all day long.
Speed wise....20mph*for the 9.8 and 25mph* for the 20 one up.
*on a good day

kaman · 15 March 2017, 00:28

Howdy.

I've got a Honwave 3.5ae (aluminium floor) as well as a Honwave t3.8 (air floor).

I own a Tohatsu 20hp 4 stroke (same as merc / mariner) and a Suzuki 2.5hp 4 stroke as well as a Suzuki 2.2hp 2 stroke.

The little Suzuki 2.5hp 4 stroke is the mutts nuts for trolling. The Suzuki 2.2hp stinks when trolling ' give me a sore head after a while so I get where your coming from.

The Honwave 3.5ae with 20hp Tohatsu 4 stroke idles along in slack water at around 2 - 3 mph. Speed varies greatly upon tide / wind etc. Sometimes idle won't push against the tide where I fish.

2 up the Tohatsu 20hp pushes the Honwave 3.5ae along at around 19 mph. 1 up around 23mph.

The T3.8 Honwave airfloor is a little faster and you can add 2 - 4 mph on that quoted above for the 3.5ae aluminium floored version.

In summary I'm happy with the 20hp. Can be used for trolling and has a decent turn of speed to cover some distance as well.

Slayer33 · 15 March 2017, 14:19

Thanks for the replies!

I think what I'm going to do is buy the mercury 20hp, they have an extended 5 year warranty offer right now til the end of the month and Basspro just has all other manufacturers beat in terms of pricing.. by about $1000 minimum.

I think I can get a different prop also to slow things down, but it sound like the trolling speed will be right around where I want it so that should be good.

Fenlander · 15 March 2017, 15:14

If you are OK with lifting the Mercury it sound the best deal for you. Yes you could prop down in pitch at the expense of possible over-revving when flat out lightly loaded.

Slayer33 · 15 March 2017, 16:19

its heavy, but its between the Suzuki and Yamaha in terms of weight.. +/- 10lbs...

Slayer33 · 15 March 2017, 21:46

Well, I pulled the trigger.. unloaded my Nissan 2 stroke in the basspro parking lot to a nice gentleman and walked in and bought the Mercury 20hp.

Pick it up tomorrow! thanks everyone for their input!

dave3235 · 15 March 2017, 23:19

Quote:

Originally Posted by kaman

Howdy.

I've got a Honwave 3.5ae (aluminium floor) as well as a Honwave t3.8 (air floor).

I own a Tohatsu 20hp 4 stroke (same as merc / mariner) and a Suzuki 2.5hp 4 stroke as well as a Suzuki 2.2hp 2 stroke.

The little Suzuki 2.5hp 4 stroke is the mutts nuts for trolling. The Suzuki 2.2hp stinks when trolling ' give me a sore head after a while so I get where your coming from.

The Honwave 3.5ae with 20hp Tohatsu 4 stroke idles along in slack water at around 2 - 3 mph. Speed varies greatly upon tide / wind etc. Sometimes idle won't push against the tide where I fish.

2 up the Tohatsu 20hp pushes the Honwave 3.5ae along at around 19 mph. 1 up around 23mph.

The T3.8 Honwave airfloor is a little faster and you can add 2 - 4 mph on that quoted above for the 3.5ae aluminium floored version.

In summary I'm happy with the 20hp. Can be used for trolling and has a decent turn of speed to cover some distance as well.

Hi all

I run a 13p Ballistic prop and get consistent 24 mph at 5680 Rpm 2 up , with 30 stone plus .I would like to try a 15 p but funds.Not sure how the 17 inch leg has different gearing , as it is an ex M L i engine

berat · 16 March 2017, 07:55

Quote:

Originally Posted by Slayer33

Well, I pulled the trigger.. unloaded my Nissan 2 stroke in the basspro parking lot to a nice gentleman and walked in and bought the Mercury 20hp.

Pick it up tomorrow! thanks everyone for their input!

This is going to be a nice configuration, it has a great voice like wishpering when trolling.