Pontoon Boat & Deck Boat Forum

Hey All,

We were looking at a boat with a high thrust 50hp Yamaha but someone here suggested we may want something bigger on our 20 boat.

Our options are the F70 or the high thrust T60. Can anyone tell me the difference and why we should choose one over the other?

Thanks!

Sam

(Edited because I can't spell)

The F70 is basically the same as a high thrust 60, with 10 more advertised horsepower. I have seen tests that say that might be optimistic. The 70 has 16 valves.
I believe they both use the same lower unit (the high thrust part)

Both have the same displacement and lower unit, take the T60 OR make the jump to the F75 for a bigger block. On a standard pontoon I find the lowest rated HP of a given block size is usually the best engine to grab. The T50,T60, and F70 will all perform the same for most of the throttle range and you will only really notice a difference in top speed. Your only looking at probibly 2mph difference for each 10hp jump.

rancherlee wrote:Both have the same displacement and lower unit, take the T60 OR make the jump to the F75 for a bigger block. On a standard pontoon I find the lowest rated HP of a given block size is usually the best engine to grab. The T50,T60, and F70 will all perform the same for most of the throttle range and you will only really notice a difference in top speed. Your only looking at probibly 2mph difference for each 10hp jump.

This goes completely against my philosophy of powering a boat. So I just gotta ask why would or what would the advantage be of under-utilizing the real power potential of a given engine block? I'm in the camp of buying the most power potential the engine builder offers in a given series. Please explain your reasoning....

rancherlee wrote:Both have the same displacement and lower unit, take the T60 OR make the jump to the F75 for a bigger block.

I've kinda wondered about this very thing. When I bought my boat a couple of years back, it came with a yamaha 50 hp four stroke.... I wanted a bigger engine and the largest that my bennington was rated for was the yammy f75, but only if I upgraded from 23 to 25 inch tubes, which I did.... now I see that same boat is only rated for the f70.... I don't know if the F70 is better, but my motor is only 2 years old and runs just fine, so I'm sticking with it for as long as it keeps purrring along.

On a planing hull boat OR straked toon' I'd have to agree, bigger the better. On a regular toon all 3 motors will make the same amount of torque and will all perform the same below 4500rpm, I'd actually go as far as saying the F70 is cammed more aggressively to make 70hp and might actually be a touch weaker/less fuel efficient below 4500rpm. It all depends on his intended uses. If he wants to drag kids on a tube, the F70 isn't going to do any better than a T50, the T75 sure would though! If he just wants run around the lake @ WOT and needs to go 22mph instead of 19mph then get the F70. Maybe he is on a budget and the 1500$ differance could buy him a nicer trailer, fish finder, or other accesories. The point is, the F70 is a great motor for a lighter planing craft rated for a 70hp. If his toon is rated for 75hp or higher the F75 is a far better choice OR save money and get the T50/60.

T50/60/F70 are 966cc, 70hp is alot to ask from that size!
F75 is 1598cc, over 60% larger block!

rancherlee wrote:On a planing hull boat OR straked toon' I'd have to agree, bigger the better. On a regular toon all 3 motors will make the same amount of torque and will all perform the same below 4500rpm, I'd actually go as far as saying the F70 is cammed more aggressively to make 70hp and might actually be a touch weaker/less fuel efficient below 4500rpm. It all depends on his intended uses. If he wants to drag kids on a tube, the F70 isn't going to do any better than a T50, the T75 sure would though! If he just wants run around the lake @ WOT and needs to go 22mph instead of 19mph then get the F70. Maybe he is on a budget and the 1500$ differance could buy him a nicer trailer, fish finder, or other accesories. The point is, the F70 is a great motor for a lighter planing craft rated for a 70hp. If his toon is rated for 75hp or higher the F75 is a far better choice OR save money and get the T50/60

I think I'm following your thought now.. Most if not all manufactures make just a few given lines of motors. By given a line of motors based on the same lower unit and block. They then de-tune the most efficient block with the most horsepower to satisfy the needs of hull designs insignificant to handle the power, or restricted horsepower lakes, they therefor then reduce the power and thrust of the primary motor. That said if allowable by law to utilize a more powerful choice in a given block line why not. Like stated above their may not be much difference between the F70 and F75 but the F70 is a much lighter motor in weight and weight matters in boating. But then again if the boat is capable of handling the F75 motor it may full well be capable of carrying the F90 which is the parent motor in this series.. The additional ponies would be beneficial in an increase speed and power to overcome the additional weight of a larger class of engine...

Why would anyone take on an extra 100 pounds for 5 horsepower?
Get the highest HP for the block size.
I was either going for the F70 Yamaha or the 115 Merc (out of virtually the same F75 block)

Torque gets you up to speed, HP is how much speed you can have (Especially with 1 speed transmissions) I can guarantee 3 identical pontoons, one with each 966cc blocked engine, would all accelerate the same and handle heavy loads the same. The only advantage is the F70 might have a 2mph advantage over T60. The f70 on my boat would
Probibly have the same top end speed as my johnzuki but I'm willing to bet it wouldn't have enough torque @ 4000rpm to get my pontoon up on plane with a full load as mine struggles too but still manages to because of the 1324cc block, the F75 would plane mine even easier due to torque. Same applies if he wants to lug a tube behind, F75 would give a bit of a thrill, the F70 on the otherhand would be just as sluggish as the 50/60hp block it's based on.

Put the biggest motor the transom will handle. That extra 2 or 3 mph will make a difference. Also, resale will be higher with the larger motor.

The F70 breathes better because they have 4 valves per cylinder.

I am still not convinced the extra 5 HP is worth the extra 100 pounds, going for the F75. If you do that get the 90 Yam or 115 Merc.

My compliments to all on a good, intelligent discussion. It all makes sense now.

Thanks for the discussion.

The 2 conclusions seem to be:
1. Save your money and go small
2. Go for the power and get the big one

We are not towing tubes but I can see the need to get somewhere quickly (like out of a storm like the one we were in last night - gotta love Florida weather in the summer!)

Boat is only rated for 70 so the 75 (or 90) is out. I am leaning towards the 70 but it likely will come down to total package price vs. budget.

I know it sounds strange but fuel consumption was part of my decision process. My 70 is still cruising around 1.1 gallons per hour over the 130 hours or so I have been running it. (total fuel I bought divided by the hours on the gauge)

Are you limited to Yamaha only (yamaha owned boat company, or Yamaha only dealer?) Suzuki has the DF70a that's a beefy 1502cc in size with lean burn also. They also come with a 6 year warranty BUT they do lack dealer network size. Yamaha has 3-4x more dealers and its usually easier to find a dealer for warranty work. I still say T60 over F70 though if there is more than a 500$ price difference, that extra 1-2mph won't save you from a storm.