is it worth repowering an 87 johnson 120hp with 3000+ hours

[suzukidave]

So I'm trying to decide if it is worth replacing the power head myself on an 87-88 johnson 120 with maybe 3500 salt water hours on the original lower end? If so, how much work is involved in dropping a replacement power head on? I've done motor and tranny swaps on cars before myself but just light maintenance on outboards. From a distance it looks like it's a matter of stripping everything off the powerhead, unbolting it, and reversing the process. The questions I have are:

-How many hours can i expect to invest to get it done and
-what else should I do "while I'm in there" and how long is the additional part list over and above the power head?
-Are the bolt in power heads offered for sale online decent?
-is a fresh power head likely to cause problems for the lower end?

I have an opportunity to pick the motor up from a friend and this would be a winter project. It has lost significant power over the last couple of years and it idles/runs rough when hot and is "just worn out" according to the dealer (haven't yet talked to dealer directly). It has been dealer maintained since new averaging about 150 hours in summer salt water per year, then winterized and a spring tune up by the dealer every year. The lower unit has given no trouble and the gear oil is changed annually and has never shown contamination. I haven't seen the bills yet but apparently the only major issue it has ever had is with the power trim which was replaced or rebuilt a few years ago.

 

[Dhadley]

Re: is it worth repowering an 87 johnson 120hp with 3000+ hours

Maintained properly 3500 hours shouldn't be that bad. I'd do a compression and leakdown test to establish where you're at. Then do a very thourough decarb and check again. You may be surprised.

 

[Walker]

Re: is it worth repowering an 87 johnson 120hp with 3000+ hours

If you decide to do it your biggest problem will probably getting the powerhead base bolts and nuts off.
Salt does wonders to them.

 

[suzukidave]

Re: is it worth repowering an 87 johnson 120hp with 3000+ hours

dhadley, I won't throw in the towel on the old block if I get it, but if I do pick it up it's not free so I'd like to figure out my "worst case" scenario.

walker, thanks, yes i guess those bolts could be trouble. I'll have to take a gander.

 

[funpilot]

Re: is it worth repowering an 87 johnson 120hp with 3000+ hours

It took me an evening to remove my 1990 90hp powerhead, and a morning to replace it. Another afternoon to do a link & synch and test it. I took a lot of pictures.

A new powerhead might run you a $1800.

Rebuilding it yourself will cost between $600 and $1000 depending on if you replace all the bearings (knowing the history of my motor, I elected to keep my old bearings) including parts, machining and supplies, and it is a lot more fun. It took one week to get the machining done, another to clear up some glitches on parts, and another to get the time to dive back into it.

Replace or test the thermostats, check all the cams and cam followers for wear, rebush the linkage, and check your fuel lines. Check for the metal float bowls, I'm not sure when they switched to plastic, but the plastics didn't hold up to the fuel and warped. Rebuild the carbs.

Of course, if you try to take the powerhead off, and the bolts are seized due to salt water use, don't be surprised if you have a dickens of a time with the motor.

good luck,
fp