Older 40 Johnson vs. four stroke 60 or 75

[purplesage]

Just returned from 10 days at a long reservoir in Oregon. Great time but long reservoir and large loads proved difficult. Now I am thinking new motor. The boat is a 21 ft. Lund Angler built in 1994 and the motor is also a 1994. It doesn't have many hours on it and ran like a top BUT. My question is will a 60 or 75 be a big enough difference to really make a difference and am I really fighting the basic hull speed as much as being under powered. I don't want to get into a situation where I am just throwing fuel at it and pushing tons of water. The 24 mile run took over 2 hours but I only used 12 gallons of fuel.

Just hoping some one has made a similar trade and can add some input. For example does the additional weight change the dynamics of the boat and I would of course have to carry more fuel. Let me know your thoughts and here is a picture of the trip - thanks Jon

 

[Silvertip]

Re: Older 40 Johnson vs. four stroke 60 or 75

Pontoons are built for comfort, not speed or fuel efficiency but you already know that. More HP translates to more speed and more HP also translates to more fuel. More speed is a rather difficult number to establish however. You will not double the speed by doubling the HP. 40 to 50 may increase speed by 2 MPH. 40 to 60 may get you two more. But here is what you really need to consider. A 40 HP engine will burn fuel at roughly 10% of its rated HP/hour. So 4 gph on what you have now. That same 10% applies to any outboard. So if you add a 75 HP motor you are now looking at 7.5 gph and I can attest to that as my 75 is fitted with a fuel flow monitor and at WOT that is exactly what it burns. So you would nearly double the fuel consumption at WOT. Now here's the rub. Running at the same speed as the 40 did at wot would mean the 75 is loafing so fuel burn might be very close to the same since the 75 is not running wide open. You then would have the reserve power available for the "loaded heavy" situations -- although you also must accept the higher fuel consumption. There is no free lunch here.

 

[lncoop]

Re: Older 40 Johnson vs. four stroke 60 or 75

A thimble will hold what I know about four stroke motors, but don't they get better fuel economy than a two stroke? Seems like that would factor in, but as I said, thimble. In any case, if you have an opportunity to upgrade to a 75 I would encourage you to do so. I think you'd find it was worth the trouble. Great pic by the way. Love to see more if you have some handy.

 

[2 Eagles]

Re: Older 40 Johnson vs. four stroke 60 or 75

Yes a 4 stroke does get better fuel economy and is much queiter than a 2 stroke. My dad just upgraded from a 50 HP 2 stroke to a 115 Hp 4 stroke last fall on his 21' Crest Pontoon. We used less fuel this summer and went out more than last summer. Do some resreach before you buy the new motor. My dad bought a brand new still in the crate 2009 for a third of the price of a 2010 all because it was the last years moldel. It came with all warranties that started the day he bought it just like buying a 2010. The only reason he didn't go bigger is becuase the boat was only reated for 115 Hp motor.

 

[The Rooster]

Re: Older 40 Johnson vs. four stroke 60 or 75

Jon, if you like the boat and plan on keeping it for a long time, I'd consider the upgrade, especially if you will be doing these kinds of excursions often w/ that type of load. Heavily loaded and underpowered is not a good feeling. That "94" motor should be carbed. The newer direct injected 2-strokes and 4-strokes are very efficient at cruise speeds. Just my .02 !!! Beautiful pic.

 

[Silvertip]

Re: Older 40 Johnson vs. four stroke 60 or 75

Yes a 4 stroke does get better fuel economy and is much queiter than a 2 stroke. My dad just upgraded from a 50 HP 2 stroke to a 115 Hp 4 stroke last fall on his 21' Crest Pontoon. We used less fuel this summer and went out more than last summer. Do some resreach before you buy the new motor. My dad bought a brand new still in the crate 2009 for a third of the price of a 2010 all because it was the last years moldel. It came with all warranties that started the day he bought it just like buying a 2010. The only reason he didn't go bigger is becuase the boat was only reated for 115 Hp motor.

I question that claim -- especially when numbers are based on observation rather than numerical evidence. Yamaha has without a doubt the best resource for comparing two stroke vs four stroke engines on virtually any kind of boat you can imagine. First -- look at noise. At wide open throttle 2 and 4 strokes are really close on the noise numbers. Yes - four strokes are quieter but not by much. The significance is the "type" of noise. Two strokes at just sound different than four strokes. Next is fuel consumption. There is no way a 115 4S is going to burn less fuel than a 50 2S on the same boat. In other words -- show show me the data. Back to Yamahas site, compare identical boats with both two and four stroke engines and look at the fuel consumption charts. If you compare the numbers at the same RPM on both motors you will see the 4S almost always beats the 2S. But look at the speed difference at those RPM. A 2S will almost always be pushing the boat faster than the 4S at the same RPM. So compare fuel economy at the same speeds, not the same RPM. Remember tha 2S fires each cylinder every revolution where a 4S fires each cylinder every other revolution. The difference in speeds vs rpm is because the 4S needs a higher ration gear set to get anywhere near the hole shot a 2S provides. So do your research and make sure you understand what you read. Four strokes are nice but they also have far more stuff to go wrong. Two strokes don't have camshafts, timing belts/chains, oil filters, valves, etc. I have both 2 and 4 strokes. Each has it's place and each to his/her own.

 

[newbie4life]

Re: Older 40 Johnson vs. four stroke 60 or 75

My dad bought a brand new still in the crate 2009 for a third of the price of a 2010 all because it was the last years moldel. It came with all warranties that started the day he bought it just like buying a 2010.

I question the above statment too -- a new Yamaha 115 is around $12k MSRP... You can buy them all over the 'Intra-web' for around $9k... You were able to buy a 115 for around $4k?

Silvertip - your 10% rule is SPOT ON. I never thought about it until you stated it, and it's dead right. Our 40hp Yamaha used 4 gallons while we were crossing some big water at nearly wide open throttle. Took an entire hour to do it.

 

[Jeep Man]

Re: Older 40 Johnson vs. four stroke 60 or 75

Older 40 hp Johnsons is going to burn more fuel than a new one of the same, so to compare to a current 60 or 75 would not be fair. I have a 60 hp 4 stroke Merc on a 20' and at 80% WOT I would use between 3 and 4 gallons for a 2 hour trip. I like the 60 but if I had the choice again I would go for a 75 and probably a 90. On a pontoon, even this would only give me 3-5 mph increase. If Johnsons are in your blood, check out a late model E-tec. They are a 2 stroke but performance is comparable to a 4 stroke.

 

[steelespike]

Re: Older 40 Johnson vs. four stroke 60 or 75

First thing I noticed is your 40 used 12 gallons in a little over 2 hours.It should burn about 4 gals per hour that silvertip suggested. Was your time closer to 3 hours?
Do you have the prop size and rpm and speed lightly loaded?
As suggested gph(gallons per hour)between 2 and 4 strokes is a wash.
Keep in mind the 4 stroke has many many more moving parts.They require oil changes just like your car.They have more,more complicated service intervals.
You should check out the direct injected 2strokes like the Etec,
The Etec has no breakin period,no service required for 3 years or 300 hours.
Meets or exceeds all CARB requirements.The Etec 40,50 and 60 are based on the same motor this makes the 60 a relatively light 240 lbs.About 60lbs heavier than your 40.

 

[purplesage]

Re: Older 40 Johnson vs. four stroke 60 or 75

I do want to thank everyone for the input (don't know why the picture was so small but I will try a couple more anyway). I will do some checking into the newer 2 stroke motors because I am still concerned about putting so much weight out on the back end. I know all the newer pontoons do it but I wonder if the older ones were reinforced to accommodate the weight. I guess another option would be to go to a bigger motor and a "water glide". I love the boat but that seems like a lot of effort - for all that I would probably be better off just getting a planing hull.

I must say, now that I have used a pontoon for one full season, they are great rigs. As one of you said, they are built for comfort. So easy to get people to shore etc. View attachment 119128View attachment 119129

I really don't mind the 10 to 12 knots but when it takes over two hours to go some place (each way) it does cut into you hunting and fishing time. Admittedly I wasn't running WOT - I idled back to 4200 rpm rather than the 4700 I would get at WOT. But at 4700 rpm I only gained about 3/4 of a knot but the fuel consumption almost doubled. Not rock science to figure that one out. The other thing was I really noticed how hard the motor had to work when I had more load.

Anyway, any more thought will be appreciated as I start thinking this thing through. Jon

 

[Silvertip]

Re: Older 40 Johnson vs. four stroke 60 or 75

Aha -- if the engine only turns 4700 rpm at WOT then it has the wrong prop. That engine can safely rev into tje 5500 rpm range and use less fuel in the process. Your rig is what is called "over propped" (too much pitch) or else the engine is just plain tired. I suspect the former is the issue.

 

[2 Eagles]

Re: Older 40 Johnson vs. four stroke 60 or 75

I question the above statment too -- a new Yamaha 115 is around $12k MSRP... You can buy them all over the 'Intra-web' for around $9k... You were able to buy a 115 for around $4k?

Yes $5K installed & trade in old Motor.