Just got a 75 Mercury 110 9.8HP

[nexus]

Hi there-<br /><br />Just picked up a 1975 Mercury 110 9.8HP motor in what seems to be good condition. It starts right up every time, and runs pretty well. However, it seems that the power varies, sometimes it picks up really strong, and other time it seems kind of anemic in it's power delivery. No apparent rhyme or reason to why it does one or the other. <br /><br />I checked the plugs which look fine, I have proper fuel mix, and there isnt anything bound around the prop. I checked all the electrical connections and everything looks fine. <br /><br />Today I'm going to check the fuel line and pickup in the tank, had the thought last night that perhaps something is obstructing the fuel flow intermittently.<br /><br />Any other suggestions for me?<br /><br />Anyone know where I can find a service manual in PDF? <br /><br />And my propeller is in decent shape but has certainly seen better days. What is a good replacement prop for pushing an 11' avon around?

 

[Laddies]

Re: Just got a 75 Mercury 110 9.8HP

sounds like the carb needs to be cleaned --Bob

 

[Barnacle_Bill]

Re: Just got a 75 Mercury 110 9.8HP

You don't say when this occurs. Are you in the boat and running around on the water? If so, put a mark on the inner and outer hub and run it again. Then check and see if the marks are still lined up.The prop may be slipping on the hub which is a common problem on those small Mercs according to my prop man.

 

[nexus]

Re: Just got a 75 Mercury 110 9.8HP

good idea... on both points. i'll score the hub and prop before going out again. as for carb cleaning... will a seafoam decarbon treatment clean the carburetors sufficiently or should i really dig into them? i'm moderately familiar with small motorcycle engines so i dont figure an outboard will be too daunting an experience. <br /><br />if the prop is slipping, are there any "easy" fixes? or do i need a new prop shaft and prop?<br /><br />this is happening on the water.

 

[Barnacle_Bill]

Re: Just got a 75 Mercury 110 9.8HP

If the prop is slipping, a new prop will solve the problem. You may be able to find a prop shop that will rebuild it for you but some shops won't bother with the smaller props.

 

[nexus]

Re: Just got a 75 Mercury 110 9.8HP

what is a good replacement prop for this motor? i know i know.... need to check the rpms at load and all that.... but ballpark it for me, i don't have a tach and i think my prop is slipping so i dont even have a solid baseline to work from. pushing 11' avon with about 300lb load most of the time. <br /><br />i checked my local west marine, and looked online but didnt see anything listed anywhere for this vintage of motor. the prop on there now doesnt appear to be marked with any identifying number.

 

[nexus]

Re: Just got a 75 Mercury 110 9.8HP

oh yeah.... what exactly is the inner and outer hub? I see the prop and the piece inside it that is machined to accept the splined prop shaft. what/where should I mark to determine if my prop is slipping?

 

[nexus]

Re: Just got a 75 Mercury 110 9.8HP

i saw another post that suggest putting a board between the lower and the prop and then tightening the prop nut. if it slips, then you need a new hub. <br /><br />i did this and while it is defnitely tighter now than it was before, it didnt slip at all. could this be the problem perhaps?

 

[ScottyB315]

Re: Just got a 75 Mercury 110 9.8HP

Nexus,<br /><br />I have a 1970 9.8 and I recently went through the same deal with my prop. The replacement prop was about 65. I opted to just have it repropped for about 25. You'll really notice with hub wears even more, because right as you arrive to planing speed the engine will start to tac out and it will feel like the motor has fallen out of gear. But the motor would recover as soon as I backed down some. Hope this helps.<br /><br />Scotty

 

[Motor Boater Bill]

Re: Just got a 75 Mercury 110 9.8HP

If yo mark the nut and it's relationship to the blades, or the outer hub that the blades are directly connected to, you will be able to see if it is slipping. But your problem does sound like a carb thing. Anyway, there are often props for this on eBay but then you won't know if they need a hub until you get them.