What Year Model? Rated at Engine or Prop? Strong or Weak Motor?

MaPaHa

Petty Officer 1st Class
Joined
Jul 6, 2012
Messages
239
I?ve got an Evinrude 140 HP motor I believe to be a 1978 Model but the only number I can find on it is a serial number of: J0002876 I?ve looked all over for a model number but can?t find anything else. It?s the greenish/gold color from top to bottom and a white base decal on the cowling with a red, bark blue and royal blue stripe around it. It also has one of these stripes just above the cavitation plate. It has the inboard power trim vs. the older style that has the hydraulic motor outside the transom frame mount. It also has the "bubble back" exhaust manifold. Any input?

I would also like to know whether the HP on a motor of this vintage is rated from the prop or the engine. If so, what is the difference? Is this a strong motor or one on the weaker side?

I?ve got it on a 22 foot tri-toon pontoon boat with lifting strakes on all three tubes and I?m not satisfied with the top speed of about 30mph with an RPM of 5100 ? 5400 unloaded and a four blade prop from Power-Tech. Outside of the motor being a bit weaker because of age, would a newer 150 HP such as a mid 90?s Fast Strike make enough difference to justify replacing it?

I?ve got a power head for this motor that the previous owner changed out back in the 80?s and I was wondering about building it up with a bit more HP? Is this easily done or am I asking for trouble?

Thanks
 

kodibass

Master Chief Petty Officer
Joined
Apr 10, 2010
Messages
864
Re: What Year Model? Rated at Engine or Prop? Strong or Weak Motor?

its rated at the power head I have been told approx 4 hp loss at the prop but have never seen it published, is your engine a good runner ? runs smooth no hesitation, no misfiring etc. good compression test nice high numbers? not knowing your vessel condition and load it would be hard to say as to the comparasion .
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Re: What Year Model? Rated at Engine or Prop? Strong or Weak Motor?

Nobody can detect seat-of-the-pants performance difference of only 4hp out of 140. Except possibly in competition on a racing style boat it might mean the difference between winning or losing by a few seconds.

I'd say you are getting about all you can get, given the boat, load and horsepower.
 

bob johnson

Rear Admiral
Joined
Feb 25, 2009
Messages
4,304
Re: What Year Model? Rated at Engine or Prop? Strong or Weak Motor?

one problem with a big pontoon , is that you really cant go out in it alone and set it up for the right rpms, and then expect it to be anywhere near that when you load it with 7 people!!! that's a huge load change in itself, then coupled with the poor performance of that hull.....you take TWO giant steps back ward. you are in the right range rpm wise...if you don't load the boat up any more... the jump to the 150 looper from the 90s would be a step.... Id say it would be more than a 15 hp increase... maybe more depending on how much compression the old 140 is pushing, and if the 150 was in top shape...I think you can run those loopers a little higher in the rpms than the older motors. maybe its enough to just get you on plane one day , when the older motor wouldn't.. bob
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: What Year Model? Rated at Engine or Prop? Strong or Weak Motor?

It does sound as if the engine is an earlier 140 crossflow. When originally produced, the factory threw nearly every performance trick into that engine. Not much left you can do to it. 140 hp out of 99 cubic inches. Probably rated at the crank. There is about a 10-12% difference (lower) from crank ratings to prop ratings. By today's standards your 140 would probably be around 126 hp. That's a lot of difference compared to today's 150. The Faststrike 150 is the high output "bass" engine, rated at 150, but actually puts out close to 165 prop hp. Keep in mind that a pontoon is basically a type of displacement hull. They are not like normal planing hulls. You could double the hp and only go marginally faster. Possible you might get the pontoon up to 35 mph with a 150. When I went from a 35 to a 70 on my pontoon, it went from 16-17 mph to 21.
 

MaPaHa

Petty Officer 1st Class
Joined
Jul 6, 2012
Messages
239
Re: What Year Model? Rated at Engine or Prop? Strong or Weak Motor?

Thanks for the feedback from all. I wondered if that motor was about maxed out from the factory given that most of those four cylinder motors range from 85 - 115 HP with some up to 135 – 140 HP. It sounds like I should just keep it in good running condition and not try to build the other power head and just keep my eye out for a 150-175 HP. I would be happy with 35mph with a few people in the boat and down from that with it loaded. The boat defiantly gets on a plane now real quick at 3,500 - 4,000 rpm but from 4,000 – 5000 doesn’t increase the speed the way it does from 3,000 – 4,000 rpm. With 4 people it cruises on plane real easy around 4,200 rpm around 25-27 mph. I’ll base my expectations on about 15-20 HP improvement to change to a 150 Fast Strike in good condition with a decent chance it could be a bit more than that. That should let me go to the next size up in props.

Over the years I’ve improved the boat starting with a “pontoon water glide” and aluminum sheeting underneath as my first major upgrade. It did everything they said it would and maybe more as far as speed, handling and performance.

Like many of you out there, I just couldn’t leave well enough alone so I replaced the water glide a few years later with a center pontoon with a heavy duty motor transom, an inboard fuel tank and below floor storage. I built a rear swim deck at the same time with the two feet my pontoons stuck out the back. Overall this helped the functionality and flotation of the boat but DID NOT help the speed even with a re-pitched four blade prop. For speed, handling, cost and installation, the water glide was the best deal; but I love the additional flotation, floor storage, inboard tank and rear deck and ski pole with the third toon.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: What Year Model? Rated at Engine or Prop? Strong or Weak Motor?

Many of the pontoon manufacturers require that 3rd tank (pontoon) when you go to the 150 hp engine. You're are all set! You could try another prop. That engine should run at least 5500+ at WOT. If it only makes 5000, you've got the wrong prop on it and you are lugging it.
 
Joined
Mar 11, 2013
Messages
22
Re: What Year Model? Rated at Engine or Prop? Strong or Weak Motor?

Before 1986 rated at power engine, 1986-present measured at prop
 

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: What Year Model? Rated at Engine or Prop? Strong or Weak Motor?

FYI - The 140 bubbleback morphed into the 115 bubbleback after the 1985/86 re-rating...
 
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