'85 Mercury 25hp XD opinions?

[seanymphmike]

I'm looking at buying an '85 Mercury 25hp XD motor for my old SeaNymph. It currently has a '73 Mercury 20hp which is getting less and less reliable. The '85 XD should fit my boat exactly using the same cables and comes with the controls. Before I commit I'd like to know if anyone has any useful advice concerning this model. I don't want to trade one set of problems for another. The one I'm looking at is electric start with a 15" shaft. Thanks

 

[JustJason]

Re: '85 Mercury 25hp XD opinions?

Your replacing a 41 year old engine with a 29 year old engine and your concerned about reliability?

 

[seanymphmike]

Re: '85 Mercury 25hp XD opinions?

JustJason, I have been accused of being overly optimistic

 

[Sea Rider]

Re: '85 Mercury 25hp XD opinions?

Buying blindly and old engine is the worst purchase of all, for your peace of mind and wallet too have a mechanic check it, if possible to trial it at sea under wot much better.

Happy Boating

 

[JustJason]

Re: '85 Mercury 25hp XD opinions?

And probably rightfully so. There are no differences in reliability between the 2 engines as there is no real difference in the technology between the 2 engines. It really comes down to use and how well it is maintained.

Depending on how well it is taken care of, the 73 could definitely be more reliable if the 85 is a pile o crap that has sat in a barn for 20 years collecting hay... Or sitting outside baking in the florida sun. Or anything in between. If you want a reliable engine, and if you want to stick with a 2 stroke. Have a look at the Evinrudes. But with these 2 engines, you absolutely could be trading 1 set of problems for another.

 

[seanymphmike]

Re: '85 Mercury 25hp XD opinions?

Thanks to all for your advice. Now, if I'm just smart enough to heed it

 

[scipper77]

Re: '85 Mercury 25hp XD opinions?

Because of the relative simplicity of those powerheads I would think the biggest area for concern is the lower units. That is assuming compression is even and it is capable of starting and idling down without missing. Things like prop shaft seals and the condition of the gears might end up being more of a deal breaker than simple things like carb or ignition problems. I guess a lot of it depends on how willing you are to put work into the motor.

There are many guys here that like nothing more than to buy these old OMC's and make them run like new.

 

[84toyota]

Re: '85 Mercury 25hp XD opinions?

I've got an 18 hp xd which runs like a raped-ape! They can be good motors depending on how they were cared for.
Ken

 

[jbjennings]

Re: '85 Mercury 25hp XD opinions?

ON the tiller models, the linkages wear and people don't keep them tuned good or let them idle down before shifting and the reverse side of the clutch dog is notorious for wearing/chipping/etc. As stated, the lower units are good, but may need new parts which aren't cheap. I would want a sea trial, too. They are good motors. The lower crank seals sometimes need replacing.
Just curious, what's making your '73 less and less reliable? The lower units are often needing of a reseal job on those, and pitted driveshaft seal areas are a problem. If your lower unit is sealed well, and the wiring is in good condition and all electrical connections have been cleaned and the fuel system is cleaned and adjusted, your '73 should be reliable.
JMO,
JBJ

 

[seanymphmike]

Re: '85 Mercury 25hp XD opinions?

My '73 won't idle if the motor is trimmed to the 2nd trim position or beyond. For my boat to plane properly it needs to be in this 2nd position. So, I start it in untrimmed posture and then when it's idling smoothly I trim it to the 2nd position(manual trim) and quickly get under way. If I run it for any length of time(an hour?) and then cut it off it seems to vapor lock and won't restart until it cools down. Sometimes after it's been running a while it will cut off by itself and then won't restart. I've had it in the shop numerous times and have been told by two different mechanics at two different shops that that this model doesn't like to run trimmed up and that the vapor lock problem may stem from the way the fuel line runs inside the cowl from the quick disconnect to the carb. And so, I'm limited to short trips. The lower unit is in good shape. It has a new impeller and pumps well through the tell tail. It is a model 200 20 hp. I thought I had the serial # with me but if memory serves its 39883?

 

[scipper77]

Re: '85 Mercury 25hp XD opinions?

Just a wild guess but I would try running with the cowl off to see if the poor idle condition is from exhaust being sucked back into your intake.

You also might have a fuel restriction causing your carb to empty. You would have to wait a few minutes for the carb bowl to refill and then it would run fine for a short time before the problem repeats itself. This can be caused by a blocked vent or an actual restriction in the line. Another thing to consider is that ethanol will destroy original fuel lines and carb gaskets. If those haven't been updated they definitely should be.