1987 short shaft 40hp Johnson vs 1978 short shaft 35hp Johnson

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Author Topic:   1987 short shaft 40hp Johnson vs 1978 short shaft 35hp Johnson

ShenandoahIndian posted 07-03-2013 02:00 AM ET (US)
I have an old 1968 13-foot Salem Skiff (which looks like a 13-foot Boston Whaler boat). The boat originally had a 1972 short-shaft Johnson 25-HP outboard engine. The motor ran great but could not get the boat on plane with three adults; plus it drank gas like crazy.
After reading many posts on re-powering 13-foot Boston Whaler boats, I decided I wanted to find an OMC 35-HP motor to replace the old 1972 25-HP. I looked for two years and could not locate a 35-HP short-shaft in my price range.
I ended up purchasing a 1987 Johnson 40-HP short shaft. The engine runs great and drinks very little gas, but the motor is 100-lbs heavier than the old 1972 25-HP and has made the boat transom heavy (even after locating the battery and gas tanks forward).
I now have a chance to purchase a 1978 JOhnson 35-HP. This Johnson 35-HP is similar in weight to the old Johnson 25-HP I had. Do you think the 1978 35-HP motor will be bad on fuel? And, do you think I should install the 35-HP and sell the 40-HP?
Any response is greatly appreciated.
Fast15 posted 07-03-2013 06:11 PM ET (US)
I believe the 1987 40-HP is based on what was traditionally a 50-HP loop-charged engine, 45-cubic-inch displacement. It was a very popular design, but yes, for the time it was a heavy 40-HP (but light by today's standards).
Assuming it is a 20-inch shaft, electric start, it weighs about 186 -lbs.
The 1978 35-HP is a cross-flow design, about 32-cubic-inch, and is lighter than your 40-HP, but will produce much less torque; for example, it will be a little better than your old 25-HP but not as strong as the 40-HP.
Again assuming it is 20-inch-shaft electric start, it weighs 121-lbs (from the 1982 brochure, where the 35 is similar to the 1978), so you will save 65-lbs going with this engine.
I'm not sure which will offer the best fuel economy.
Fast15 posted 07-03-2013 06:12 PM ET (US)
Just re-read your post, you have a short shaft, so you will save about 5-lbs on either engine.
ShenandoahIndian posted 10-04-2013 11:25 AM ET (US)
Thanks for the input. I ended up staying with my 40-HP. The weight of the motor surely lets you know it's back there, but I can run it at half throttle at 20-MPH and 6 gallons of gas seemes like it lasts forever. This has to be one of the best boats on fuel conmsuption on the water. I'll live with the additional weight. I think the weight loss needs to come off of my 215-lb body instead! I could stand to lose 40-lbs or more, so that would surely help.
jimh posted 10-05-2013 10:15 AM ET (US)
Yes, I have noticed that people will quibble about small differences in the weight of an outboard engine, but ignore the weight difference of the people on the boat, which might be more than 100-lbs.
ShenandoahIndian posted 10-08-2013 10:40 AM ET (US)
You are correct Jim... especially on these little 13 footers. Gives me another reason to lose some weight.

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Author	Topic: 1987 short shaft 40hp Johnson vs 1978 short shaft 35hp Johnson
ShenandoahIndian	posted 07-03-2013 02:00 AM ET (US) I have an old 1968 13-foot Salem Skiff (which looks like a 13-foot Boston Whaler boat). The boat originally had a 1972 short-shaft Johnson 25-HP outboard engine. The motor ran great but could not get the boat on plane with three adults; plus it drank gas like crazy. After reading many posts on re-powering 13-foot Boston Whaler boats, I decided I wanted to find an OMC 35-HP motor to replace the old 1972 25-HP. I looked for two years and could not locate a 35-HP short-shaft in my price range. I ended up purchasing a 1987 Johnson 40-HP short shaft. The engine runs great and drinks very little gas, but the motor is 100-lbs heavier than the old 1972 25-HP and has made the boat transom heavy (even after locating the battery and gas tanks forward). I now have a chance to purchase a 1978 JOhnson 35-HP. This Johnson 35-HP is similar in weight to the old Johnson 25-HP I had. Do you think the 1978 35-HP motor will be bad on fuel? And, do you think I should install the 35-HP and sell the 40-HP? Any response is greatly appreciated.
Fast15	posted 07-03-2013 06:11 PM ET (US) I believe the 1987 40-HP is based on what was traditionally a 50-HP loop-charged engine, 45-cubic-inch displacement. It was a very popular design, but yes, for the time it was a heavy 40-HP (but light by today's standards). Assuming it is a 20-inch shaft, electric start, it weighs about 186 -lbs. The 1978 35-HP is a cross-flow design, about 32-cubic-inch, and is lighter than your 40-HP, but will produce much less torque; for example, it will be a little better than your old 25-HP but not as strong as the 40-HP. Again assuming it is 20-inch-shaft electric start, it weighs 121-lbs (from the 1982 brochure, where the 35 is similar to the 1978), so you will save 65-lbs going with this engine. I'm not sure which will offer the best fuel economy.
Fast15	posted 07-03-2013 06:12 PM ET (US) Just re-read your post, you have a short shaft, so you will save about 5-lbs on either engine.
ShenandoahIndian	posted 10-04-2013 11:25 AM ET (US) Thanks for the input. I ended up staying with my 40-HP. The weight of the motor surely lets you know it's back there, but I can run it at half throttle at 20-MPH and 6 gallons of gas seemes like it lasts forever. This has to be one of the best boats on fuel conmsuption on the water. I'll live with the additional weight. I think the weight loss needs to come off of my 215-lb body instead! I could stand to lose 40-lbs or more, so that would surely help.
jimh	posted 10-05-2013 10:15 AM ET (US) Yes, I have noticed that people will quibble about small differences in the weight of an outboard engine, but ignore the weight difference of the people on the boat, which might be more than 100-lbs.
ShenandoahIndian	posted 10-08-2013 10:40 AM ET (US) You are correct Jim... especially on these little 13 footers. Gives me another reason to lose some weight.