Tohatsu 25hp vs 30hp? Repower

[Dboii]

What's up guys I'm looking into repowering my 14 foot Livingston. As of right now it's between the 25 or 30 tohatsu. The only difference I see between both of them is the hp rating and rpm range. Any advice or maybe even other engines you guys might recommend? Here's the specs on 25 and 30

• Engine Type: Tohatsu MFS25CETL Four Stroke
• Horsepower: 25 hp
• Cylinders: 3 cyl
• Shaft Length: 20"
• Steering: Tiller or Remote Mech
• Starter: Electric + Manual
• Weight: 182 lbs
• Full Throttle Range: 5000 - 6000 rpm
• Displacement: 526cc
• Induction System: EFI
• Warranty: 5 years

• Engine Type: Tohatsu MFS30CETL Four Stroke
• Horsepower: 30 hp
• Cylinders: 3 cyl
• Shaft Length: 20"
• Steering: Tiller or Remote Mech
• Starter: Electric + Manual
• Weight: 182 lbs
• Full Throttle Range: 5250 - 6250 rpm
• Displacement: 526cc
• Induction System: EFI
• Warranty: 5 years

 

[Faztbullet]

I always suggest go to max rating...if a boat is rated for a 30 ..put a 30 on it.

 

[Sea Rider]

Yep, max it's much better specially if will be carrying more load on a larger boat. After break in period ends check with a tach if the motor revs at least middle to max of their wot rpm range if comes factory delivered with a prop for better water performance as loaded. What's the price difference between both mentioned models ?

Happy Boating​

 

[Dboii]

Yep, max it's much better specially if will be carrying more load on a larger boat. After break in period ends check with a tach if the motor revs at least middle to max of their wot rpm range if comes factory delivered with a prop for better water performance as loaded. What's the price difference between both mentioned models ?

Happy Boating ​

Perfect that's what I wanted to hear I'm gonna have to go for that 30hp for better performance. I believe it doesn't come with a prop though so I'm gonna have to see what I'm buying. Any recommendations on prop size? They quoted me 5083 for MFS30CETL and 4750 for MFS25CETL

 

[Dboii]

The Livingston is rated for 40hp remote but I believe it was rated for 2 stroke 40s since its a 1985 hull.

 

[Sea Rider]

If the motor doesn't come with a prop check with Merc's Prop Calculator which should be your starting prop, just fill the requested data, buy a prop and check the max wot rpm achieved as loaded. From there can fine tune the prop.

On 4 strokes 25 to 30 HP conversions costs huge more than the peanuts costs payed doing same on 2 strokes with equal mentioned HP. Forgot to ask, plan re powering from an existing motor you already have ? Max HP rated it's for Max number of passengers, if with much less passengers a 30 HP correctly propped will power the boat efficiently.

Happy Boating​

 

[Dboii]

I am repowering from an older engine. It is a 1987 mercury 35 hp 2 stroke. When I bought the boat the engine looked brand new and compression was about 140 on both cylinders. Runs great but some lakes I go to require a carb rated engine. Hopefully the 30 isn't so sluggish compared to the 2cyl 2 stroke

 

[Sea Rider]

I am repowering from an older engine. It is a 1987 mercury 35 hp 2 stroke. When I bought the boat the engine looked brand new and compression was about 140 on both cylinders. Runs great but some lakes I go to require a carb rated engine. Hopefully the 30 isn't so sluggish compared to the 2cyl 2 stroke

You'll be surprised what a correct prop maximization can do for your old boat, all my motors were correctly propped to run towards their max wot rpm range factory stated, those motors came factory delivered with a prop that didn't do their respective homework right. Now it's a day/night boating difference powering larger boats lightly to medium loaded.

Happy Boating

​

 

[Dboii]

Hmm you're right maybe that's why the owner included 2 props I'll check out the prop sizes and do a water test. I'm thinking of keeping the engine because I do use the boat mostly in saltwater and freshwater will be mostly 3 times a year. Efi is nice though compared to having to choke it in the morning

 

[JimS123]

IMHO, displacement is the key. These 2 motors have the same block. The specs show that the 30 is getting 5 more HP due to the increased RPM.

BTDT. In the past my experience is that going to higher RPMs with the same motor provided an insignificant improvement.

If the cost differential is peanuts, then go big. If not, the 25 will be more cost effective.

 

[Sea Rider]

Great idea to keep the old 35 HP motor which it's a 2-3 cylinder one ? to get the max out of it will need to install an induction tach to test both props as currently loaded, a simple water test will only determine that the combo is running under power, not a big deal water test at all. Need to know the min-max wot rpm range factory stated for that motor and stay with the prop that achieved the highest wot rpm numbers towards max range.

Don't think that a 250 wot rpm increase for the 30 HP will bump + 5 more HP, ECU's are different, different timing advance and some other hidden tech issues...

Happy Boating​

 

[Dboii]

The 35 hp is a 2 cylinder engine. I ended up ordering an induction tach from Amazon. Gonna have to do a little bit of research on hooking it up

 

[Sea Rider]

The 35 hp is a 2 cylinder engine. I ended up ordering an induction tach from Amazon. Gonna have to do a little bit of research on hooking it up

Great, is that a tiller or central console boat ? Which brand/model will that tach be ? induction tachs are very easy to work with, just follow the install procedures for a 2 stroke, 2 cylinder motor specially the spark plug firing sequence adjustment.

Happy Boating​

 

[Dboii]

It is a 14 foot Livingston with a small center console. I actually just bought 1/4 inch ply gonna try making a little bigger console steering wheel is too low. First time doing it so hopefully everything works out good. It is called searon bought it from Amazon

 

[Dboii]

I ended up buying the 30 tohatsu. Put the 35 mercury 2 stroke for sale. It's a 87 anyone have a reasonable price to sell it for. Last tested had 150 compression on both cylinders rebuilt carb and it comes with control box and throttle plus shift cables. Runs excellent