18hp 'rude w/ 25hp carb...exceed 18hp max on boat?

[cwinfrey]

Hey everyone,

I just bought an 18hp evinrude (1971) 2-stroke that is equipped with a 25hp carb, apparently bumping the hp up to 25hp. I was told this doesnt change the torque, but just adds more RPM's to the motor, allowing it to get to that 25hp mark...
My question is, can I go with a boat that is rated at 25hp max, or should I go under that and get a boat rated at 18hp, or 20hp? The motor still weighs the same as an 18hp, but I guess puts out 25hp now. I know this should be a question I can answer myself...I would think I shouldn't go under a 25hp max rated boat...

Also, its states in the owners manual that putting a 25hp carb on the engine is perfectly acceptable.

I guess the reason I am asking is because I was reading that it isnt recommended to go above the max rated hp on a boat because of weight issues, stability issues, insurance issues, legal issues, etc... But I am also thinking that because we are talking about such a low hp rating that it would be OK to get a boat rated at 18 or 20hp and not have to find a boat rated at 25hp. Everything I have read so far talks about much larger boats with much higher hp ratings and higher motor hp ratings.

Thanks!
Chris

 

[Chinewalker]

Re: 18hp 'rude w/ 25hp carb...exceed 18hp max on boat?

For starters, the 25hp carb did NOT make your motor a 25. If anything, it might have bumped up a horse or two. More differences between the 18 and 25 than just the carb. Personally, I'd find an 18 carb for it, as it'll likely run better with very little, if any performance drop-off, and will be better on fuel...

 

[metriccrescentwrench]

Re: 18hp 'rude w/ 25hp carb...exceed 18hp max on boat?

While looking for a boat I'd be more concerned about finding a boat that fills the needs of what I want to do with it rather than looking for one with some arbitrary max hp rating. For instance, if you're going to do a lot of fishing I'd be looking for the largest boat that I could easily transport (within reason) because of the added stability and comfort.

 

[jdsgrog]

Re: 18hp 'rude w/ 25hp carb...exceed 18hp max on boat?

I hope you didn't pay for the motor thinking you are getting a 25hp.

 

[cwinfrey]

Re: 18hp 'rude w/ 25hp carb...exceed 18hp max on boat?

Ok, thanks for the criticisms guys.

I dont honestly believe it has 25hp now. And if I put an 18hp carb on it, I dont believe it has 18hp...its nearly 40 years old.

And no it didnt buy it because I thought I was getting 25hp, it was priced very nice and was totally overhauled. The only original parts are the block, head, shaft case and prop. Everyhting under the cover is brand new on the outside. And rings, seals, etc have been replaced.

I will be fishing and waterfowl hunting out of it. I want a wide boat for hunting because its difficult to put 2 grown men, a dog, and gear in a boat, then try to shoot 12 guage shotguns out the sides of the boat without feeling like im going to get wet when hunting in a narrow boat. Im looking for 14 or 16 foot, and at least a 48" wide floor at near the stern.

The question is, can I get a boat rated for under the hp of my motor and still be safe. Since we are talking about such a low hp, I would think its ok to get a boat rated at 15hp or so. I wouldnt want to go as low as a 10hp rated boat.

 

[ChrisAG]

Re: 18hp 'rude w/ 25hp carb...exceed 18hp max on boat?

I have a 14' (actually 13'6") Starcraft Sealite rated for a 15. I tried it with an older 18 and it was fine. The 18 is much bulkier than my "newer" 1978 Johnson 15 but not much heavier - maybe 90 lbs versus the 77 lbs 15.

The 18 ran the boat 1.5 mph faster than the 15, so we are not talking a major difference in speed or weight. If you get another couple of mph with the "25hp" carb it would be no big deal.

I agree putting the 18 on a boat rated for a 10 would be a bad idea.

However I would like to see you blast some holes in the aluminum boat with your shotgun. might cut down on wind resistance so you'll go faster.

 

[cwinfrey]

Re: 18hp 'rude w/ 25hp carb...exceed 18hp max on boat?

Im not too concerned with the whole concept of my 18 with a 25carb on it. it just happens to be that way. if it was an 18 with an 18 carb on it, i still would have bought it...i only paid $500 for it. And im not really concerned with the 1 or 2 extra mph I might get. I dont boat far when I go out because i obviously try and find the closest boat launch to where Im going, not the closest boat launch to my house, I may travel a couple miles in the water, so getting there 38 seconds faster by going 1 or 2 mph faster isnt a huge deal. my concern is putting my motor on a boat rated for less than what I have in my motor. If I had to guess, seeing that my motor is almost 40 years old and was at one time rated at 18hp, even though I have a larger carb on it, i bet it still only has about 18hp. Im sure the larger carb is compensating for the 40years of use and power loss. I know it hasnt been used constantly for 40 years, but still. The guy I bought it from said it sat for about 7 or 8 years before he got it and overhauled it....Im gonna find a boat rated at 15hp or more...