Selecting a mid range four stroke

[Olybird]

I see there are a lot of posts asking advice on repowering, and should I buy this brand or that. I'll try to keep my questions sucinct and to the point. I have a 20' aluminum fisihing boat (Gregor). The boat has a maximum hp rating of 75, and the weight limit in the stern (motor, battery, etc) is 430lbs. Obviously the weight restriction is doable for any 75hp four stroke, however I really want to keep my 8hp kicker on the back which weighs 80lbs. I use my boat for trolling for salmon (among other things).

So, I can go with a Yamaha, Suzuki, or Honda 75 hp, but I would probably go with just one motor and get rid of my kicker in that senario. Is the verdict in about the ability of this size four stroke for trolling at low RMP's for long periods of time? Manufacturers will tell you they're fine, others will tell you that they "load up" and ruin the plugs.... help me out here please...

Yamaha has introduced a new 70hp four stroke that is 100lbs lighter than the competitors 75hp. This is great because I could keep my 80lb kicker, but I'm really concerned about not having enough top end power. If I spend the money I want a little more top end then my 70hp Johnson two stroke.

Any guidance is appreciated!

 

[DJ]

Re: Selecting a mid range four stroke

I doubt a 70 HP 4S is going to have more top end than your 70 2S. Maybe, but it would be negligible.

Post 1983 HP is pretty comparible.

Go for the weight savings, if you can find it. I would have no issues with any of your choices.

We have a 75 Merc. 4S on a 20' Toon. It is now three years old and has about 300 hours. It has been flawless. I will NOT say it is light though.

Keep us posted on your choice.

 

[Olybird]

Re: Selecting a mid range four stroke

Thanks for the quick reply. Yes, I agree that the new four stroke 70hp by Yamaha likely won't have more power then my existing motor.

What do you think about trolling the mid range four stokes? I like the idea of having an auxilary motor for safety on one hand, but on the other hand I like the idea of having one relaible motor to maintain instead of two...

Thanks again for your help!

 

[DJ]

Re: Selecting a mid range four stroke

Olybird,

Our 75 Merc. 4S trolls down quite nicely. However, that is on a 20' toon with a toon rated prop. (low pitch). We troll for Stripers in So. Alabama.

I have no issues with a "kicker" if you have the room and can handle all the other "stuff" that goes along with it.

I think you are on the right track in thinking about weight, few do. Good thinking.

Plus, may I add? Buy from a dealer you know and trust. The best outboard, on paper, is not worth spit if you cannot get it fixed/serviced.

Service is entirely the reason I went to Merc. I'm a John/Rude guy through and through. But, our local Merc. dealer is a GEM!

 

[Olybird]

Re: Selecting a mid range four stroke

Still seeking additional advice on this topic. Go with heavier 75hp and skip the kicker, that means trolling the main motor, or go with a lighter version, say the new Yamaha 70hp (260lbs compared to the 350lb other 75hp), and keep the kicker. Are there others that are trolling frequently on this size motor?

thanks a lot for the advice!

 

[sdsaw]

Re: Selecting a mid range four stroke

Olybird,
The new efi 4s troll just fine at low rpm as long as you are able to go slow enough for the fish that you pursue
I have a 115 Merc 4s that I can troll at idle speed all day long without issue at 1.8 knots.
My buddy has a 17ft. Key West cc with a 60hp Merc efi 4s that trolls at the same speed at idle in gear.
I have heard that it is recommended to run the motor hard for 15 min or so after trolling for extended periods to help burn off the gasoline that may have saturated the engine oil.

Whatever motor you choose, do not forget to install a fuel/water separator to protect your VST and injectors that the efi motors have

 

[Olybird]

Re: Selecting a mid range four stroke

Thanks a lot sdsaw! I appreciate the input and I've been hearing that the four stokes will troll fine, and that you may be able to adjust the prop pitch to get slower speeds if neccesary.

Thanks again!

 

[marcortez]

Re: Selecting a mid range four stroke

FYI......the "new" model F70 will not be available for purchase until sometime in June, according to Yamaha Motors in Georgia.
I tried.....dealer in SoCal says "no can get now"

Lots of idling and slow speed operation has a tendancy to "make" oil in the crankcase.
The cause of this is not enough heat, allowing unburnt fuel to get into the crankcase....which on checking the dipstick......will reveal "over the full mark" and thinning/diluting the lubricating oil.

A hotter thermostat will help the engine run a bit "hotter" and burn the fuel more completely......thereby avoiding some of the fuel making it's way into the crankcase.

I would not recommend changing a thermostat on a NEW motor.
That would be up to you.

I know what I speak......my Honda 4 stroke "made" oil and the servicing dealer relayed the "fix" is to install a hotter thermostat.
Bingo.....no more fuel in the oil.

On edit:.....the Honda is a carb model and not EFI....and I cannot say with certainty that an EFI model will be affected with the "making oil" syndrome.