1969 merc 1250 performance issue. please help

[ajax5240]

I just bought a fiberglass 16'er with a tower of power 1250 on it. I am an automotive tech but new to the boat world. The motor fires up good and sounds good. Today was the first run at the water. Came up with two issues

1. - the motor will not come up to full speed, at full throttle it sounds like its bogging a little and won't come up on plane. What should I check first? Compression, timing, carb adjustment?

2. - it sounds like reverse is not engaging correctly, sounds like it goes in gear ok, but when you give it some throttle it makes a grinding like it is coming out of gear. Reverse seems good out of the water with the muffs on.. is there linkage adjustment that I should make to get it to engage fully?

Thanks for any help!

 

[194269]

Re: 1969 merc 1250 performance issue. please help

I would run a compression check first, then I would check the idle needle setings. Turn needles in untill they just touch bottom and then turn back out 1 & 1/2 turns. If the engine still boggs then give each one a 1/8 turn more. Two stroke engine need to idle rich for acceleration.

 

[waynelk]

Re: 1969 merc 1250 performance issue. please help

Always try to take a test ride BEFORE buying a boat. Solves a lot of problems. Now that you have it do a compression test. All cylinders should be the same within 5 - 10 psi. Could be the prop is too big for the boat. Also Lynk and sync is very important for the inlines. Get a manual and check it. Carb adjustment is for idle so if it starts and idles fine doubt thats the problem. Fuel pumps going bad or carb float levels to low will cause it to bog and not plane along with the big prop and timing sync. For the reverse problem remove the cover and follow the shift cable to the slide. Put it in reverse to see which way it moves, then there is a round barrel on the threaded part of the cable which is for adjustment. If you go too far it will not be in neutral when in neutral. Should turn free in neutral with no clicking noise. So don't move the adjustment too much. If it works out of the water on muffs it is probably not off by much.

 

[ajax5240]

Re: 1969 merc 1250 performance issue. please help

I got the engine performance issue handled, was a broken plastic piece on the shaft that locates the distributor. However, even with the gear selector adjustment all the way in the reverse still does not engage right, any thing else to try? Or is the reverse gear fried? Any help would be GREATLY appreciated!

 

[Gomer50]

Re: 1969 merc 1250 performance issue. please help

I had the same problem with my reverse awhile back.I did this first with the boat in the driveway I diconnected the battery from the motor,put the motor in reverse and had my buddy hold on to the flywheel tight while I got ahold of the prop and tried to turn it.If your lower unit is good you wont be able to turn the prop.
If bad you will feel how it is jumping out of gear.Possible bad clutch dog, shift pin not fully engaging, or bad gear.Which means you will have to tear her apart to fix.I included some pics to kinda show whats what.

 

[ajax5240]

Re: 1969 merc 1250 performance issue. please help

Got it in reverse and held the flywheel with a breaker bar, prop did not turn. Realized that the control cables were making a pretty tight bend from me relocating the controls. Re-routed them, re-adjusted, and locks solid into drive and revers just past the detent. Thank you for all the help and pointers!

Can someone walk me through the process of setting the timing on this motor, I know that I need to get a repair manual soon, but if someone can give me a quick step by step I would really appreciate it!

Next project is rigging up a tach on this hot rod. I have the harness that plugs into the front of the control box, but am i correct in believing that an automotive tach will not work right with a marine engine? If so, what is the least expensive option for a tach, and what wire goes to what connector on the tach from that control harness?

Thanks again for all of your help guys, you have made this project some together much quicker!

 

[Gomer50]

Re: 1969 merc 1250 performance issue. please help

For your application the tach needs to be a 6 pulse or 12 pole application.And no auto tach dont work for these motors.This is the one I use (cheap but works and looks good)

http://cgi.ebay.com/ebaymotors/ws/e...viewitem=&_trkparms=clkid=1955797944417237569