New jet rig

[JoshKeller]

decided I didnt want to spend time rebuilding another boat and sold the alumacraft. picked up a tracker grizzly 1648 thats already set up exactly what I wanted. stick steer, open floor. It came with a blown 75/50 johnson. I am putting my 50/35 on it now, but how much more can I expect if I rebuild this 75/50? Bottom cylinder appears to have broken a ring and it chewed up the piston. Bore still surprisingly looks great. Its a 3 cylinder motor vs a 2 cylinder for my 50.35 so it definitely weighs more. However, its the large pump vs my medium pump.

ive got no doubt my 50/35 will push it, as this boat tows much easier and is so much easier to move around by hand than my fisher is. Same trailer, the fisher is just that much heavier.

 

[smackdaddy53]

Check out Texas Outboard Rebuilders, I am buying a rebuilt Merc 90 from them October 17, put the deposit down two weeks ago. Four year warranty, they ship anywhere in the US and are great to talk to and deal with. $4250 for the motor I am picking up or $2500 to totally rebuild the old one. I even had Chris Carson send racing reeds to them and they installed them while rebuilding it for no extra charge. (Not that its hard to do.)

 

[JoshKeller]

im actually looking to rebuild it myself. Ive rebuilt a few. If it'll be worth doing, i'll tear down the powerhead, and do the cylinder that needs it. From the way it looks by pulling the head, a hone job will get the bore smoothed up, and a new piston/rings/needle bearings should have it up and running.

 

[Lil' Blue Rude]

From the pics on scream and fly it looks like it broke a ring think you can actually see a piece stuck in the piston. lol Your 75 is a 49cube motor. The 56 cube blocks do better with a jet because they make more low end torque then the 49 cube did. They started making the 56 cubes in 1986 and the keep making the 49 cube until 1988. They use the same crank just different block, rods and pistons. 3.00" vs 3.1875" Plus the porting a lot different. The 49 cubes are motor of a top end high rpm motor vs a 56 which makes more low end torque. Doubt there's too much difference between the 50/35 you have now and the 75/50. Hard to beat a omc 2 cylinder with a jet.
https://forum.tinboats.net/viewtopic.php?f=48&t=18544&start=75 Here's a link to a build were he started out with a 49 cube and swapped to a 56 cube powerhead. The 56 cube had a little motor work done but doubt it was anything to drastic but they are a lot stronger motor with a jet then a 49 cube is.

 

[JoshKeller]

Took it out today but didnt have a passenger since kayla was sick. It ran pretty good, about the same speed as the fisher did. 5400 RPM and approx 22 mph. I need to tweak the motor height a bit. luckily it was windy and cold so i had the river, and ramp to myself to make some adjustments. Third highest hole it did best, but had some spray coming up into the mounting bracket, and a little into the back of the boat. The highest hole was too high, but had no spray, so I need to find a way to split the difference. This boat lifts and runs on plane so much higher than my heavy fisher ever did, even with two batteries and myself way up front, vs the fishers mid console.

A few questions... can I slot the upper mounting holes like the bottom ones are?

Also, with just me in the boat, and no weight in the back is it normal to have a rooster tail a few feet higher than the cowling when running WOT? It seems to go away pretty much below 3/4 throttle. I didnt mess with trim at all, its just tucked under fully. Im wondering if no weight in the back to a balance it out is what was causing the spray on the third hole?

thanks guys

 

[smackdaddy53]

I don't see why you could not slot the top holes as well and get it tweaked to the right height then drill two holes in the middle holes through the transom and have 6 mounting bolts. More is better right?

 

[dhoganjr]

Slotting the holes will work fine, but do it 1/8 inch at a time till you find the right spot.

Before you slot them try running it on the 3rd hole an trim it out a hole to see how it runs and if you are getting as much spray.

 

[Lil' Blue Rude]

You won't have any problems slotting the top hole on your bracket. I've done it to my 40/28 and my 60/40 both to fine tune it.

 

[JoshKeller]

took it out this evening and messed around.. talk about a huge improvement after cleaning the carbs and shimming the impeller. this was the second hole trim out, first hole lost 1 mph but had a little better hole shot. I dont think i'm going to mess with the 75/50 or try to get anymore out of it than this.

this was with all my fishing gear, me (235 lbs), and kayla (115 lbs).

 

[smackdaddy53]

Nice!

 

[dhoganjr]

Looks like it is doing great!!!

If you got the time and it won't cost much, fix up the 70 and sell it.