Pontoon Boat & Deck Boat Forum

I had a new Yamaha 115 put on back in April. Have just now got it up to the 20hr mark to change the oil and fluids. My question is how fast should it be going? It doesn't seem to be going much faster than my 90hp 2 stroke. And between 4rpm and 5+ rpm there is only about a half mph difference. It seems like it struggles at WOT. Any comments or suggestions? I have also tried adjusting the trim and no luck. Thanks in advance

What's the rpm at WOT? It should be at 6K rpm and if not, you'll need to re-prop it. For every pitch inch difference changes it about 200 rpm.

The 115 FB puts out almost 126 hp. Sounds like you have prop issues not a motor issue. I run the same engine on a 23 ft 2 toon Suncatcher w no strakes. Today, with 3/4 tank of fuel and 3 people , we ran 28 mph. Without knowing your specific set up, nobody can really give you any insight.

Wot is about 5200 rpms. It's on a 25ft Bennington usually with 3-6 ppl... It was acting like it wanted to bog down when I would turn at wot and jump up to around 6k rpm, but has stopped doing it. Speed on a good day is roughly 14 mph

Jake202 wrote:I had a new Yamaha 115 put on back in April. Have just now got it up to the 20hr mark to change the oil and fluids. My question is how fast should it be going? It doesn't seem to be going much faster than my 90hp 2 stroke. And between 4rpm and 5+ rpm there is only about a half mph difference. It seems like it struggles at WOT. Any comments or suggestions? I have also tried adjusting the trim and no luck. Thanks in advance

I agree with the others that said it sounds like it is a prop problem... I have a 75 hp yamaha and the last time I checked it by gps I was getting 24 mph with two people and half a tank of gas.... I damaged the prop a few years back and went with a prop the dealership recommended ( not what came with the boat )... new prop was horrible, turns out I was overpropped.. went back to the original and now at wot I'm running right at 5950 to 6000 rpm's... I believe ( not positive ) the alarm sounds at 6200....

Ok so after I figure out what type prop I have, what do I start looking for? I am a newbie when it comes to this part

You defintely need to get a different prop. Is that your normal load? I dont think your ever going to be happy though, a 115 on a 25 ft boat is under powered. But i bet you can get better preformance with the right prop. Good luck

That is the normal load for us and the boat is only rated for a 115hp.

Jake202 wrote:That is the normal load for us and the boat is only rated for a 115hp.

You need to get your rpm's up to near max, which should be 6000 rpm if i remerber correctly.
I dont know much about your model boat. I guess i figured a 25 ft boat should have atleast a 150 hp but thats what i get for thinking!

Drifter wrote:

Jake202 wrote:I guess i figured a 25 ft boat should have atleast a 150 hp ...

Normally I'd agree with you; however, on a Toon it maybe too heavy for his transom .

I have a 115 on a 24 foot toon. At 5000'rpm full tank of fuel three adults I am getting 16-18.