New 4 stroke to replace old 2 stroke size issue.

[rschnack]

Hi again,<br /> I did a search and found alot of pros and cons comparing 2 and 4 strokes but did not really find an answer to my question. I have a 1970 16' runabout that I am restoring. It now has a 1970 85hp Johnson that is so far doing well but I am considering replacing it a some point with a four stroke. The boat is rated for 100hp. My boat is a single vee that becomes pretty much flat at the stern and weighs 810lbs. The 85hp Johnson weighs 265lbs. I've looked mostly at Hondas and Mercuries, and some others. It seems, to stay in the same weight range, I need to stay in the 50-60hp range. Higher than that the weight of the motor seems to jump ~100lbs. The boat is very quick with the 85hp. If I understand correctly the horsepower is measured differently on the new motors so a new 60hp may not be hugely different than the old 85hp. Does anyone have experience going from a larger old two stroke to either a large or smaller new four stroke? I like the way the boat handles now and am concerned about adding this much weight to the stern Any imput would be greatly appreciated.<br />Best regards,<br />RCS

 

[pine island fred]

Re: New 4 stroke to replace old 2 stroke size issue.

good thinking being concerned about the extra weight. have a 16 ft. pro line ctr consel. had a yamaha 50 2 stroke. motor burned a con rod so i replaced it with a 80 yamaha 4 stroke. what a mistake. toooo much weight in the stern. sure the boat jumps on plane but any speed off plane the boat is real stern heavy, waffels, constantly hits the bottom. suggest you get a bathroom scale,put bricks/blocks in the stern to simulate the extra weight and see how the boat performs off plane. suggest you check out the merc 3 cyl 2 strokes [ called classics ] just got one,teriffic motors. regards fred.

 

[rschnack]

Re: New 4 stroke to replace old 2 stroke size issue.

pine island fred,<br /><br /> Thanks for the input. I am even more concerned now that I have cut the transom open to replace the rotted plywood. The original ply was only 1 1/8" thick. I am not sure if it will support a 385 lb. motor. I'm going to have to think about this a little. <br />Best regards, <br />RCS

 

[JB]

Re: New 4 stroke to replace old 2 stroke size issue.

I went from a 1980 Evinrude 100 to a 2001 Suzuki DF70 4 stroke on my Boston Whaler Montauk 17 and haven't regretted it for a minute. <br /><br />I moved a bit of weight forward (battery to the console) and the trim is unaffected.<br /><br />Lost about 6mph WOT but only need about 1/3 as much gas for a day of fishing.<br /><br />Good luck.

 

[rschnack]

Re: New 4 stroke to replace old 2 stroke size issue.

Thanks for the input JB. I knew you had made this switch and was hoping you would respond. The hull designs of our two boats are pretty different but I think the results will be pretty close. If I put on a heavier motor I may install a permanent fuel tank forward to replace the two 6 gal portable tanks that I keep in the rear. That should balance things out a little. First I have to see if both the boat and myself survive it's restoration. Wish me luck!<br />RCS