new old guy with new old motor

[beerfume]

Hi all,
first post, been lurking in the shadows for some time now... I recently purchased a '78 (?) Bluefin Sportsman 16' bowrider aluminum that I hope to restore. Included was a '75 Merc 500 ornament on the back, not hooked up or even bolted down. No reliable history. The original engine on this boat was a 70 hp Johnson and the boat is rated for up to an 85 hp. My question is " how does one determine whether this motor is worth consideration? Firstly, is it enough engine for the boat? Second question is where/how to begin to assess this motor. I studied the FAQ "awakening a sleeping outboard" with great interest", however, buying a manual, waterpump, plugs, dismantling things, carb cleaning etc seems like the second step to me as you've already committed time and money to something that might actually be better suited to the job of anchor. Can I screw things up royally by just hooking up a battery, gasline and garden hose and crankin 'er?
Final question, I have a '72 Kiekhaeffer 500 for parts, are these 2 engines compatable?


" I got my sh*t together, but I forget where I put it"

 

[Frank Acampora]

Re: new old guy with new old motor



The rule of thumb used here is that you should power with about 75% of the hull's rated horsepower for best performance. With that rule, your 50 would be a bit underpowered. BUT: It does not take into consideration your use.

Many factors, including emotional go into determining if an engine is worth repairing/restoring. How do you feel about the engine? Does it have major mechanical problems? Is there a LOT of corrosion making it likely to cause problems on disassembly? Etc.


Since you already have the engine hanging on the boat, you may as well try jump starting to check compression ratio on all cylinders. If it is high and equal, then attach electrical and check for spark. If it has spark and substantial compression you are gold. It should take only relatively minor work to get it to run.

Back to the rule of thumb: This boat is rated for 90 horsepower. Originally it was powered by a 55 and served adequately. As my son became older he wanted to waterski. As he became more proficient, the engine became too little for our needs. I repowered with a 90 and we enjoyed many weekends skiing.

 

[gm280]

Re: new old guy with new old motor

Yes, you have to take many things into consideration on whether to rebuild any outboard engine. The age is one as well as the overall external condition too. Reason for that is usually the external condition could tell a lot about how that engine was maintained. But most any outboard can be brought back to life...and I might add for less than the price of any new engine of similar size too...in most cases. BUT, there are limits to how much each person is willing to invest for that option. Only you can make the final decision, but bear in mind, the age of such an outboard NOT running will not get you very much money if any these days. Others will go through your decision process as well thinking about buying it. As for me, I am a go getter and would most certainly revive that outboard just because it would be a nice challenge to me. Not that it would be cost effective or anything else, but because I enjoy making old things new again and that is just me...

 

[brnschoneck]

Re: new old guy with new old motor

depending on how whe looks on the outside us ur better jusdgment to me almost any ol o/b is worth fixing just cuz of their reputation once u get her going she gnnna goooo a lonng time !!! Again may not be in ur budget etc.....

 

[beerfume]

Re: new old guy with new old motor

thank you gentlemen for your considered opinions. Asthetically the engine looks really good and its very clean under the wrapper. I'll proceed following Frank's outline, measure compression and check for spark. I've read lots on these procedures already. Take a few pics as I go. It's still falling quite a bit below freezing here at night so I may have to wait a week or two before hooking muffs to it. I suppose it is somewhat under powered for the boat but probably good enough for a fishing boat. As you guys have pointed out I already own it and it seems the concensus on here is that these old 4cyl mercs are a decent enough motor.