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97 mariner 75 hp jets

Thanks Timguy I guess time will tell .I questioned the precious answers because part number's are the same on the 75 and 90 engines mercury used many different carbs wme 49,59,62,64,75,78, ect. All have the same parts except the jets . and it seems that if a larger jet gives you more top end rpm then a 75 hp with a top rpm of 5250 and the 90 is 5500 larger jets should give the increased rpm giving more hp. Not finding any info yet I will keep doing research. I hope to talk to a friend of a friend who is a Mercury master mechanic and works at Power Broker marine soon and pick his brain I will post what I find out
 
timguy said:
Big dog, Mr. Scott and I have had a few run ins over the years and I still consider him a wise mechanic. Racer can flex his muscles too, we are all human. The objective here is to exchange information with respect and modesty. What launched things off here was your continued inquiry after our techs advised and you questioned.....in itself is fine, in fact I enjoy that. Finally Mr. Scott snapped a bit, calling you a "know it all". His bad, but wait.....I think he has always been this way and we accept it, don't think much of it. You and I are similar age and also heavy equipment/marine mechanics. Sometimes these simple little 2 strokes can kick your a**. But I have gained nearly 5 hp with a jet change....and prop, with a 25/30 Johnson. It is not unrealistic to think that your Merc/Mariner cannot add 10 or 15 hp assuming that the 75 is simply a "detuned" 90
You need to mind your own business!!!!!! Stop making excuses for me because I for one especially do not like it!!!!!!!
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Sorry, Mr. Scott. I just wanted to get into this thread to make some suggestions I have some experience with jet mods on these motors. I kind of understand you and you will always have my respect no matter how you try to belittle me. You are a wise man and your help here on the forum is appreciated.
 
timguy said:
Sorry, Mr. Scott. I just wanted to get into this thread to make some suggestions I have some experience with jet mods on these motors. I kind of understand you and you will always have my respect no matter how you try to belittle me. You are a wise man and your help here on the forum is appreciated.[/

To the people I respect it is time to leave this forum. When ass kissing and lying is become acceptable things I gotto go. Thank you it has been fun and thanks for.the great experience.
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Sorry guys but jets wont turn it into a 90..need tuner and carbs. I know for a fact that the venturi is larger along with the emulsion tube...the throttle plates are the same. I have converted one 80hp (same as 75) to a 90hp and customer picked up about 5mph....think I still got his old carbs in shed.

 
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Great info, thanks Pappy. My Dad always ordered or purchased lower horsepower in each displacement series thinking it would mean longer motor life and better idle/ low speed operation. He was probably correct. He wanted just to "get there", and not always be the first in the race.
 
Im not looking for a argument, just an education . When an exhaust tuner is mentioned in posts are they referring to the exhaust plate or exhaust tube ? And I addmit I was wrong about the carbs beeing the same, there is a differance but after spending the afternoon at a Mercury dealer talking with a Master Mercury Mechanic and owner the only thing we could find was differant was the carbs and main jets. now I have to decide if I want to spend the money for 3 new carbs to pickup 750 rpm and possable 10 mph
 
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No problem bigdog, everyone has a goal, I was raised in the Ontario wilderness and reliability and longevity, as well as economy, are all key to success as well as survival. When getting a boat up on step is the goal, or picking up time, then that 70 can be "powered up". Outboard replacements can be " out of budget", for sure.
 
So after much research I found out going from 75 hp to 90 hp can be done .But with only a gain of maybe 3mph its not worth it so i will stay at 75 hp .
 
Right, to each his own, eh? For the cost of used carbs, kits, possibly and most likely a different prop, it might not be worth it. Every application dictates direction and every direction is dictated by available funding. Most of us can use the money somewhere else where it can go farther. Another consideration is economy, especially when we are looking at mpg under 5. My twin 25s, while freighting, do about 4 mpg. The twin 30s here ran about 3 on the same boat. Speed difference was negligible, but you could certainly add more cargo weight, perhaps 2 more 200 pound passengers plus their bags.
 
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