Home › Forum › Ask A Member › 80’s/90’s 50hp opinions?
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johnyrude200.
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November 24, 2015 at 5:23 pm #27612
I actually have seen a number of the 80’s 50hp motors floating around, so I’m thinking that I may pull the trigger on one this weekend, and pick up a few others as back up parts donors should it be necessary. I’m looking at this as a motor to be a daily driver for a few years so parts are always useful of course.
Too bad I didn’t snag up the 5-10 of them that went to the scrap yard earlier in the year…this was before I was dealing with anything above 25hp…
November 25, 2015 at 2:39 am #27646IMHO, stay far far away from anything that has Chrysler FORCE on it !!!
ack ack ack spit spit – terrible taste in my mouth from having two of them.jus my Dos Centavos
December 8, 2015 at 7:57 pm #28240So I have to ask, what is the major difference in the 40/50hp motors? I was looking at the parts diagrams and see the cylinder heads are different (the 25 & 50’s seem to have the same ones), and the crank case is listed as different part #’s for the 40 & 50, but the cranks, rods, and pistons are all the same. I’m sure the carbs have difference high speed orifices, but I’m not seeing much other than the usual.
I’m hoping T2stroke can shed some light on this one, as I know part #’s may only represent a color change, nothing physical. I ask, because I recently picked up a nice early 90’s 40hp and parts motor ’86 50hp, and am wondering if it’s possible to convert to a 50hp.
At the very least, the 50hp has what appears to be a good, complete powerhead…am potentially considering a swap out of powerheads if the 40 can’t be converted via cylinder heads and carbs..
December 8, 2015 at 8:44 pm #28241When I rebuilt my 80’s 50-60 horse motors, I noticed the cylinder sleeves were installed slightly different from each other. The ports don’t line up fully so this is probably how OMC adjusted the horsepower of these motors.
December 9, 2015 at 1:57 am #28264First off the first motor with the new replaceable sleeves is a 1980 60hp. These motors are referred to as 45 cu. in. motors. (44.9 actual) Talking about two cylinder engines here. OMC earler and later made a three cylinder 55hp and 50hp.
The 45 cu in motor was built in 40,50,60hp models as well as a 48SPL (just a 50hp without VRO or any other features). The 60hp was dropped when prop rated hp motors came into being.
Comparing the older motors (pre 1989) can get you in a lot of trouble. The motors look the same, but several things changed. First off and the biggest that will give you trouble is the gear shift boss on the bottom of the powerhead. When building powerheads and buying scrap blocks we had to keep an eye out for just what we were buying. You can’t get around if the wrong boss block is attempted to be used on a model engine it wasn’t designed for. The commercial engines get into this because of the different gearcase. There are other more subtle differences (mounting bosses for electrical items). Those could be worked out, but not the shift mechanism with out major work or possibly swapping front halves which I don’t consider a proper fix.
As far as the power differences from model to model, OMC/BRP will do that with carb differences when possible. The easier/simpler/cheaper the better. Usually it is carb throat/venturi size. The sleeve is the same for a 40/50hp motor. As far as it being put not matching the aluminum ports, that happens everyday with all manufacturers. That is not by design to limit horsepower, although it certainly does do that. Sleeves also move from time to time, especially after an overheat. Keep in mind the only thing that holds those sleeves in the block is the machined fit. The factory does not put the sleeve in as tight as rebuilders do. (Ease/speed of manufacter)!
I was lucky to have worked for OMC for 25 yrs and then worked at a rebuilder/parts distributor for another 5yrs. I got to see both sides of how they said it was done and how it got done, by all the manufacters. We sleeved/bored about a 1000 motors a yr. during my tenure.Dan in TN
December 13, 2015 at 9:28 pm #28554So – delving into a 1991 40hp evinrude that a customer brought to me today, with UFI. Can somebody help me locate where to find the retrofit ignition kit to turn this back into the non-UFI configuration? Tried looking it up under Marineengine.com but having some trouble locating it.
April 28, 2018 at 9:53 am #74919Old thread revisited. I have a 1996 40hp that Im beginning to suspect has the worn cylinders but high compression numbers.
It will start but seems to be a Dr Jeckle personality. Plenty of power from 1/2 throttle up, but will fade out much below that consistently regardless of engine temp and when restarted seem to run like it’s too rich (shake/unsteady idle – NO SNEEZING OR LEAN RUNNING characteristic) and not be able to get up in RPM’s. It will not idle down to below 1,000 RPM without fading out. You can catch it by re-priming to stop the stall.
Shows 130/130 for compression, good spark. Ive already rebuilt the carbs and did a link N sync.
Does this sound like a familiar scenario to anyone?
Dan you mentioned early in this thread that you can switch back to the earlier metal carbs; this has the plastic top ones. Im guessing the pre-89 fixed jet metalcarbs would NOT work on a later model motor?
April 28, 2018 at 4:04 pm #74939Well, Casey’s technique for evaluating one of these engines is spot on for sure….But, we do need to be careful, just cuz it won’t idle does not mean it is wore out…Compression seems to be normal, but we realize this is not necessarily an guarantee all is well inside. Are you able to peek inside the cylinders with some sort of inspection light? Generally speaking, even an engine with plenty of wear will run OK below half throttle, it just fades away and dies at low speeds/dead idle. So, am I reading your post correctly? You mention that the engine dies out at any speed below half throttle but can be revived with the primer. You have done sync/link, did you check flywheel TDC position?
At this point, I would try to peek inside the plug holes to see if there is excessive scoring or aluminum transfer…If all seems "OK" inside, I would pull the carbs apart. Just kinda sounds like the low speed circuits are plugged up….
What did the customer report? Did the engine run OK last year, but refuses to idle this year? If so, I am more convinced there is a carb problem.
Again, I sure don’t want to condemn this powerhead because it won’t idle….Do you have carbs from a known good idling engine you could substitute?April 28, 2018 at 5:25 pm #74947Don, heres an update.
I ran the motor on muffs for about a half hour, and IKNOW I KNOW this is NOT how you calibrate them, but was able to reproduce the symptom. Motor starts and runs, bring it down to below 1500RPM (on muffs), and it started running erratically. Load up, drop a cylinder, then run fine, etc.
Playin with the low speed adjustment had no rhyme or reason.
So I pulled the carbs and replaced with two other ones and >so far< it seems to be running right and idling down lower.
Im heading down to the ramp to run it on a test prop and will submerge that sucker lower than it should be to see how it responds!
April 28, 2018 at 5:55 pm #74950ok, so different carbs helped, good info…Again, I just don’t want to condemn this thing cuz it exhibits symptoms of a worn out powerhead….
"load up, drop a cylinder, then run fine"…..
A worn out powerhead won’t recover/save itself…It will just kind of fade away/stall at idle, kinda like it was running out of gas…
I am always suspect when I see the carb/sync adjustments all jacked up/out of whack, usually the result of a futile attempt to solve powerhead problems with sync adjustments… -
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