1976 Evinrude 200, low rpm/ low power

[bigsbetter]

This is not my engine...It's my brothers, but he needs some help. He's got this old motor on a brand new boat. The boat weighs 2500lbs loaded. It's a 1976 200 hp Evinrude. The compression is 85lbs on all cylinders. (a little low?)The max rpm he has been able to get out of it is about 4700-4800. That is with a 14.25 X 24 3 blade Raker prop and speed was 41 mph GPS. I loaned him a 13.5 inch diameter 21 pitch 4 blade prop. This is where it really doesn't make sense. The engine now turns slower @ about 4600 rpm and he lost 2-3 mph. Both props have the pitch stamped on them, and are in great condition. He has replaced the spark plugs with the factory perma-gap plugs. He's had the carbs off several times and they are immaculant. He's tested the power packs and they jump the required spark gap. He's tried different octane fuels and uses Evinrude 2 cycle oil. @ 50-1 ratio. The engine just doesn't seem to be putting out anything close to 200 horsepower. The tag on the engine says the operating range is from 4700-5700rpm and @ 5250 is 200 hp. Does anyone have any ideas on how to get more rpm out of this engine? Or what the ideal prop size would be for a 200 hp Evinrude.

 

[topher312]

i have a 78 evinrude 235 which is one step up from the motor that your brother has. the OMC factory specs say that there may only be a 15 psi difference between each cylinder. but since you said that they are all at 85 you dont have a problem with that. however, the specs also say that the minimum compression should not be under 100. i have not started my motor yet, but i think i'm gonna do rings and gaskets and that should bring back the compression. this is what my motor is putting out for comp. 1/90 2/80 3/90 4/80 5/85 6/80. so im in the same situation as your brother as far as the comp goes. but i think that if he does rings and gaskets it should restore some compression. the only thing that i need is a powerpack because my whole right bank is dead. let me know how it tuns out. that motor that he has is a beast when its running at 100%

 

[2benchanted]

1976 200

I have the same motor that sounds like it is time for some rings.The 76 is one of the strongest running 200 cross flow.I did a comp test and all of mine were 110 to 115.If he has the factory heads that end with a letter then he has the good heads.The combustion chamber should look just like the top of the piston and not like a bath tub.Re ring it and shave the heads to 130 psi and that motor will scream.I have mine on a enchanter about a 1200 lb boat and it turns 4800 with 5 people and 15 gal. gas at 55 mph.Good luck:cheers

 

[bigsbetter]

Thanks for the replies. Sounds like he's just overdue for a re-ring/rebuild.

 

[irvin mccurry]

same 200

have the same engine, found out one carb was not giving rpms, cleaned once, tried it yesterday and had to take it (the middle one) off 4 times. it is soaking in cleaner now, if it doesn't give more rpms tomorrow i am beat. all cyl have 100 comp across the board, anyone?

 

[caddman]

check other fuel components for restrictions....alsocheck for bad hoses if it can suck in air it will and no power will result, the more rpms the worse it will get.....

 

[ezflyer]

check other fuel components for restrictions....alsocheck for bad hoses if it can suck in air it will and no power will result, the more rpms the worse it will get.....

i would also check the exaust. sometimes spiders and little bugs will build a nest and plug them up. also running the gas/oil mixture to rich will also plug the system up as well. this will not let it turn up as the motor must breath. the faster u can get the air in the faster it must come out.

 

[irvin mccurry]

jumping out the hole

thanks caddman and ezflyer found the gasket was missing from top carb, runs like a scalded ape now

 

[irvin mccurry]

have not figured out how to post a new question now so i'm stuck here. would a non marine battery such as a semi battery or any other battery damadge my marine rig or should i stick with deep cycle marine batteries, clueless if there is any difference and would it make a difference?

 

[Rob B]

have not figured out how to post a new question now so i'm stuck here. would a non marine battery such as a semi battery or any other battery damadge my marine rig or should i stick with deep cycle marine batteries, clueless if there is any difference and would it make a difference?

Go to whatever forum you want to post in, click on post new thread to start another one. Personally I would stick with marine batteries instead of car batteries. I know my Evinrude has to have high cranking amps for the on board computer and other electronics.

 

[72_mx_13]

i would also check the exaust. sometimes spiders and little bugs will build a nest and plug them up. also running the gas/oil mixture to rich will also plug the system up as well. this will not let it turn up as the motor must breath. the faster u can get the air in the faster it must come out.

50-1 is really the lowest that you want to run it, i run my motor at around 40-1 but thats just my thought

 

[barry reiland]

bigsbetter,
That motor may not be tried it's the wrong pitch prop! I have same motor and about same weight boat and I'm running an 18 pitch Raker and runs 5700 RPM (light load) and (gps) about 48-50 MPH depending on temp/humidity. With a 20p I had 5100 and tried a 22p and got about 44-4600 all slower. That motor is rated 200 hp at the crank and only about 180 at the prop. In 1987 or 88 they started rating HP at the prop. 90 psi is about normal for that motor and could be run on regular gas. 100-115 if you shave the heads, witch I did to increase the compression but now have to run premium fuel and gained maybe 1 MPH. Try a 19p Al (3blade) or 18SS or 17 SS 4 blade which are all equal. When going from AL to SS drop one size also from 3 to 4 blade drop another one size, been at it 20+ years on this motor and 2 complete rebuilds. Also read the plugs,on that motor they run pretty dark almost black when hot and humid and only tan color on cool days, like under 50 degrees.
Pull all 6 plugs and compare, if any are different check that cylinder for fuel/spark.

2benchated
You also should drop a couple on pitch sizes 4800 RPM's is to low and is loading down the motor granted that was loaded. Light load and cool temp should be up to 5750, maybe 5000 fully loaded on a 90+ humid day. With more RPM's you will get more speed and a better hole shot.

 

[happy]

I'm running a 175 crossflow "mid 80's" on my ski-mate, one of the best products for carbon is a product called "sea foam" I've been using this for decades. It works. It will also clean out the rest of the motor as you run. This will help that ol timer a bunch. Thats all I run in my fuel tanks, this is a stabilizer too. try it. you'll see the difference!

 

[irvin mccurry]

gone

headed to west marine for sea foam, new tach and to see if someone there can fit me up with some new bow railings, much obliged!

 

[Bill Gohr]

OK so I didn't read this earlier, so you have a real 76 200 ( the strongest one we made) and it only has 90 psi? look at the head gaskets, there is a little tab at the top, does it have a "V" notch in it? this motor should have all of 120 psi and turn 6K effortlessly, original heads?

what boat is it on again and what prop? Seafoam, no, use OMC engine tuner.

All carbs cleaned obviously, fuel pressure? spark on 6? indeex the flywheel?

If you can't get it just call me 847 356 3245

 

[happy]

Is there something about seafoam we should know? I believe Seafoam made the omc stuff, is this correct?