1976 Merc 9.8 rebuilt, won't go WOT...in forward..

[benyshep]

I rebuilt the powerhead with a new piston, rings, needle bearings due to needle bearings failing. Also relaced the damaged rod. I also rebuilt the carb, all using a Seloc manual. The motor ran, but I had trouble getting the idle set, and no WOT on the water. I took it into a marina and $130 later, I had a coil replaced and the carb and timing set. The mechanic decribed the problem as a "flutter" in the high end, and said it could be fuel delivery problem, float, jet, or reed box. It will now run about 1/2 to 3/4 throttle and then sound like its choking. If I pull the choke out, it gets worse. Funny thing, it will run WOT in reverse, where I presume there is less of a load. Using a GPS, it pushed my 12' jon boat about 7 MPH at first, then slows to 6, then 5 1/2. If I run it WOT in reverse for a bit, I get the same cycle again going forward, with faster at first. I'd appreciate any help to locate the problem. I'm thinking the float needs adjustment..........any clue?

 

[wildbill123]

Re: 1976 Merc 9.8 rebuilt, won't go WOT...in forward..

HOLY COW!!!! I registered today to ask exactly the same question!!!!!! My dad's Merc is a 1975<br /> 9.8 that we can't figure out. It's been about 6 years since we had it in the water and it's doing exactly the same thing. The last people to touch the motor were the guys in the shop who went thru it as part of an insurance claim. We ran it again last Sunday and found that the motor revs up to it's normal range in "forward" while my dad was attempting to "slip" it somewhere in between forward and neutral. The boat speed remained the same but for the first time it actually sounded like it was running properly in forward. We concluded that it must be in the lower unit. But once again, what would cause it to work perfectly in reverse and so poorly in forward??????? Thanks

 

[benyshep]

Re: 1976 Merc 9.8 rebuilt, won't go WOT...in forward..

I tried what you mentioned and that didn't work. I drove it around for 2 hours today varying the throttle for the break-in. It ran best when my fuel tank was running out and it was sucking air. The boat went from 6MPH to 11.5 MPH in an instant. It has the correct jet in the carb. Does anyone have a suggestion how to either lean out the high end or increase air intake to possibly solve this problem? Thanks.....

 

[benyshep]

Re: 1976 Merc 9.8 rebuilt, won't go WOT...in forward..

I guess I should make sure the float is set right first. My manual shows when the carb is upside down, to measure from the bottom of the float to (I believe) the carb base. This should be 1/4". When right side up and the float hanging, the manual wants me to measure the distance from the bottom of the float to the top of the main fuel jet. This should be 1/64 - 1/32". On this meaurement, I am unclear if it means from the bottom of the float directly above the jet (which would make the float hang lower), or to measure from the lowest part of the float off to the side (which would make the float hang higher). Also, any general input on what float adjustment would make it leaner on the high speed might help.........

 

[wildbill123]

Re: 1976 Merc 9.8 rebuilt, won't go WOT...in forward..

I have no idea about carbs. I have somebody take care of that for me. My next plan of attack is that I plan to take the old fluid out of the lower unit and make sure that it gets new pure and clean. I have heard that it's possible that the shop that put it into storage added an anti-freeze of some sort into it. At best I'll get peice of mind with all new fresh lube in there in the proper amount. Took out top vent last night and NO extra flowed from it so it must be a little low. good luck

 

[wildbill123]

Re: 1976 Merc 9.8 rebuilt, won't go WOT...in forward..

Only have access to a email computer @ work mon-thurs.<br />Will report findings next Mon.

 

[benyshep]

Re: 1976 Merc 9.8 rebuilt, won't go WOT...in forward..

I've readjusted the float to sit higher when upside down - hoping to lean out the high end. If this doesn't work, I'm thinking of getting a smaller jet. It has a .041 in it and calls for a .039 at a higher elevation. Does anyone have any ideas how to fix this? Thanks........