'57 Johnson 18 Top Speed

[cajun555]

Re: '57 Johnson 18 Top Speed

55, that sounds like a good speed. When you sat in the front it sounds like you had to much weight up front causing to much of the boat in the water. <br /><br />I carried my boat back to lake yesterday to do some more testing. I would get my best speed with the motor set at the next to the Highest trim setting. I've figured my total weight is 1000 lbs. My top speed was 23 mph(speedo) so I'm happy.<br /><br />BTW, which F/C did you have? I've got a 56 feathercraft vagabond II. The wife and I really enjoy it.<br /><br />Let us know the results when you get your tach. I posted earlier in a post that I thought your wot rpm was 4000, its not, I checked the book and wot rpm is 4500.

 

[55Crestliner]

Re: '57 Johnson 18 Top Speed

Went today again, and again, some interesting results. Took the boys with me again. <br />I tried it with all 3 of us in the back, bow really reaches for the sky, but when it settles down, it really scoots - still 24.9, and the boat goes real smooth.<br /><br />Then I took the trim tabs off. Sitting in back was pretty scary, now I know what porpoising is! Also took longer to go to plane.<br /><br />But when we all got in front, we saw 23.6, and when the boys went in the back, we saw 24.5.<br /><br />So, my summary of the 2 inch permanent trim tabs is they are PERFECT if I was always sitting in the back, they make the boat real smooth. But when I'm in the front, which is basically all the time, they do slow it down. <br /><br />My F/C is a 1949 double deck deluxe runabout. It's in pretty sad shape, some idiot cut the front deck off to make it a better fishing boat.

 

[dhonda]

Re: '57 Johnson 18 Top Speed

hey i have a 57 crestliner viking 14' with a 1960 40hp evinrude and itl only do 25mph? Other people claim theres do 30-32mph any sugestions how to make mine do 30? it runs at 5000rpms and i tried lifting the motor pin up 1 notch and it accelerates much quicker but i didnt gain any top speed.

 

[tmcalavy]

Re: '57 Johnson 18 Top Speed

dhonda, you need to try another prop pitch. Crestliner...now you know how to distribute the weight best for your 18 hp. Mine would really make my little mid-50's 14-foot open tinny fly with two guys (500 lbs. total), gas tank and fishing gear. Jumped up faster with a whaletail on it, but was slow in turns. Without the WT, it was slower to plane but would still scoot, especially if I sat on a milk crate just in front of the rear seat with a tiller extension. Wish I still had the boat...the motor looks lonely sitting out in the shop by itself...maybe I should start looking again...who says 2 boats is 2 many?

 

[dhonda]

Re: '57 Johnson 18 Top Speed

the cavitation plate is 2 inches below the keel, is that a possible reason why it dosnt have any top speed? Also i have a hydrofoil on it.

 

[tmcalavy]

Re: '57 Johnson 18 Top Speed

Yep, that's a lot of drag for 2" below the keel...especially with the hydrofoil.

 

[dhonda]

Re: '57 Johnson 18 Top Speed

so if i raise the motor up so the cavitation plate is level with the keel how much top speed would i gain most likely? Also would it accelerate quicker?

 

[RSchendel]

Re: '57 Johnson 18 Top Speed

I have a '58 Evinrude 18 on a Lund C14 aluminum boat. With 2 adults (160 each), I get about 20MPH. I have not tried adjusting the trim yet, plan on trying it later this summer. I defintely do feel inclined to get a tach as I have no idea if the motor is reaching the suggested RPMs (4500 I think). Are the RPMs measured with the motor in the water under load?

 

[dhonda]

Re: '57 Johnson 18 Top Speed

yes they are