older HP vs newer HP

[motorboater]

My old boat a 20 foot Crestliner with plastic seat bases, no frills, and, I think, a 1993 Johnson 90 2 stroke, ran well and would usually top out at 21 mph.

The current boat is longer by 2 feet, heavier, with more “stuff” and wood furniture, and a 2004 Johnson 90 stroke, tops out at 24 mph.

This begs the question, why? Are newer motors better than motors of only 10-15 years ago? Isn’t 90 older horsepower, the same as 90 newer horsepower?

Thoughts anyone?

[ttcfan4476]

Could be a diffrent prop size or the way they rate the engines could be done a diffrent way now days.

[Bamaman]

I used to have one of the original Mercury 175 hp Black Max motors on a Cajun 18' bassboat. Later, the same motor was a 150 hp.

At one point, they started using the prop horsepower vs. the crankshaft horsepower.

[jrolin1]

I bet your pontoons are bigger and plane off now.

[pond tuuunes]

Horsepower calculations dont change, but power bands and torque curves do. Also, I think toon shapes and styles have changed. JT

[LocoCoco]

...At one point, they started using the prop horsepower vs. the crankshaft horsepower.

Yes, though that was long before '93. OMC started prop-rating their motors in about '80-'81. I believe Merc began officially prop-rating all their motors around that time too but historically they were all over the place with power ratings. ie. some rated at peak rpm, others rated at a lower rpm which meant at full throttle they really put out a lot more than the sticker read.

In this case, the older motor could have been worn out, running a different prop, gear ratio, improperly adjusted throttle linkage, or mounted too high or too low. The boats could also play a part. 23" pontoons on the older one vs. 25" pontoon on the newer one would make a difference.


LC.

[GXPWeasel]

All very good points stated already. I would guess that it is a combination of several things that are giving you the speed advantage in the newer boat. Could be better gear ratio's and torque curves coupled with bigger diameter toons, and even better shaped toons. Also, what about underskinning? Does your new toon have underskinning? I'll bet the older one didn't, and if the new one does, this could make a small difference as well.

[GregF]

Yamaha forced American manufactures into rating at the prop in the late 80s when they started doing it.
The original Yamaha claim was that their 90 was almost twice as powerful as an American 90.

They did bring us loop charging, oil injection (that worked) and some other improvements that were developed in the motorcycle business. Mercury decided it was better to license the Yamaha, that to try to beat them.
My 1989-90 YamaMerc 75 was another 3000 hour motor for me and I sold it for $900.

[Bamaman]

Greg: You're a shining example that you just cannot wear these boats out. Motors, yes. Boat, no. I keep saying that pontoon boats are such a great long term value in recreation.

My 1985 24' Starcraft is still powered by the original 115 hp Yamaha 2 stroke, and it supposedly puts out 138 horses at the prop. While this boat hits "the wall" @ 30 mph on top end, it accelerates like a bass boat. My only parts purchased have been a $240 oil injection module and one $27 water pump impeller and spark plugs.

Yamaha came into the U.S. market in 1984, and immediately went after the Mercury dealers. Within 2 years, previous Merc dealers were selling more Yamahas than Mercs, and they have not looked back. It made Mercury get off their duffs, and finally make some positive changes to their motors. Merc had been going years and years with virtually no changes in their boats other than stripes.

We're in the market next year for a new tritoon w/150 hp motor. 2 stroke vs. 4 stroke? High line 2 strokes do pretty well on gas mileage. And, they'll run circles around comparable 4 strokes in acceleration. Both 2 and 4 strokes appear to have about identical top end speeds, however. Do the costs of oil changes/filters offset the cost of outboard motor oil? Both 4 stroke and 2 stroke motors are comparable in noise at full throttle, but the 4 strokes are quieter up to a point. Deciding what brand motor is very difficult at this point. Yamaha's are high quality and expensive. The Suzuki 150 hp pushes pontoons great with a bigger prop, but dealers are few and far between and Suzuki is not customer oriented. Mercury dealers are all over the place, and their new 4 stroke 150 is less expensive--and the 2 Optimax XS 2 strokes are attractive. Verado engine setup and Smartcraft gauges/controls are triple expensive, and I don't want to mortgage my granddaughter's soul to buy one. We don't have any ETEC dealers closeby. Motors are just difficult decisions to make.

[RonKMiller]

Yamaha forced American manufactures into rating at the prop in the late 80s when they started doing it.
The original Yamaha claim was that their 90 was almost twice as powerful as an American 90.

They did bring us loop charging, oil injection (that worked) and some other improvements that were developed in the motorcycle business. Mercury decided it was better to license the Yamaha, that to try to beat them.
My 1989-90 YamaMerc 75 was another 3000 hour motor for me and I sold it for $900.

That's really interesting Greg - I'm continually amazed how strong my 1988 Yamaha 90 two stroke is.

To think that it could push my "barge" to a true 20 mph (with a 14X9 prop) is just astounding. Oil injection consumption is minimal and easy to monitor. I take a look at the tank level every few days - and this is with some serious miles in between. Gas mileage isn't all that great - but considering the weight I'm pushing it makes sense.

[RonKMiller]

Greg: You're a shining example that you just cannot wear these boats out. Motors, yes. Boat, no. I keep saying that pontoon boats are such a great long term value in recreation.

My 1985 24' Starcraft is still powered by the original 115 hp Yamaha 2 stroke, and it supposedly puts out 138 horses at the prop. While this boat hits "the wall" @ 30 mph on top end, it accelerates like a bass boat. My only parts purchased have been a $240 oil injection module and one $27 water pump impeller and spark plugs.

Yamaha came into the U.S. market in 1984, and immediately went after the Mercury dealers. Within 2 years, previous Merc dealers were selling more Yamahas than Mercs, and they have not looked back. It made Mercury get off their duffs, and finally make some positive changes to their motors. Merc had been going years and years with virtually no changes in their boats other than stripes.

We're in the market next year for a new tritoon w/150 hp motor. 2 stroke vs. 4 stroke? High line 2 strokes do pretty well on gas mileage. And, they'll run circles around comparable 4 strokes in acceleration. Both 2 and 4 strokes appear to have about identical top end speeds, however. Do the costs of oil changes/filters offset the cost of outboard motor oil? Both 4 stroke and 2 stroke motors are comparable in noise at full throttle, but the 4 strokes are quieter up to a point. Deciding what brand motor is very difficult at this point. Yamaha's are high quality and expensive. The Suzuki 150 hp pushes pontoons great with a bigger prop, but dealers are few and far between and Suzuki is not customer oriented. Mercury dealers are all over the place, and their new 4 stroke 150 is less expensive--and the 2 Optimax XS 2 strokes are attractive. Verado engine setup and Smartcraft gauges/controls are triple expensive, and I don't want to mortgage my granddaughter's soul to buy one. We don't have any ETEC dealers closeby. Motors are just difficult decisions to make.

Based on my experience with Honda power equipment, motorcycle and car engines I would bite the (very expensive) bullet and buy a Honda, period. For as long as you keep your stuff I think the long term value and lack of hassle is worth every dollar. Who else in the marine business takes a bulletproof 4 banger CAR engine that has been around for almost 40 years and sticks it into an outboard casing?

[GregF]

If you run fast all the time, a 2 stroke will work for you. The manatees killed my 75. It just could not go slow most the time.
I went with the Merc 4 stroke in 2002 and they made a believer out of me. Oil changes and a filter is a lot cheaper than TCW-3 every tank of gas and they are quiet, no smoke, no sneeze stall.
It will idle around all day at 700 RPM if that is what you need to do and at 1500 I get hull speed (about all the manatee police will allow) and do quite a bit under 1 GPH fuel. My 70 Yamaha, basically a silver Merc 60 with a tweaked ECU, pushes me up around 24 GPS with me, the wife and a 110 pound dog. That is a MPH or 2 better than the Merc 60 with the actual same prop.