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Evinrude 25hp top speed problems

A

antjacobs

New member
Hi all...

I've recently brought a Eurosport 13 4m fishing boat. originally had a Yamaha 70hp on it, but the block cracked.. A friend of mine gave me an Evinrude 25 either EV or ER model but I'm unsure of the year (late 80's early 90's black casing) this week I've fitted the 25 and attached the steering, changed the throttle box, ect.. The engine itself looks like it's had very little use, good compression, spark. I've changed the plugs, had the carb off and was spotless inside, I've set the timing marks to the correct place and the butterfly is opening fully on full throttle. Yesterday I took the boat out for it's first test in the sea.. The engine ran well i was out for a good hour but the top speed was not correct. sounded like RPM was getting up there but the top speed was low. The only thing now i am thinking it could be it the high speed screw restricting the fuel as i didn't adjust this while out yesterday.. dose anyone have any other ideas of what could be causing this problem? I've been a mechanic for a number of years but this is the first outboard engine I've ever worked on and first boat I've owned... Any help would be much appreciated..

Thank you..
 
The screw in the top of the chamber above the butterfly is not an adjustment then? this was wound in tight. Today I've run the engine in a barrel on full throttle and wound that screw out a turn and a bit and it made a huge difference in the RPM the engine reached, also the manual trim was set all the way out, there are 5 holes for adjustment, I've set it in to number 2. I'm out for another test tomorrow depending on the weather..
 
If it had a 70 HP and you dropped it down to a 25 HP, it not
surprising that the top boat speed is not where it used to be.

If you ran it in a barrel at WOT, it should have kicked all
the water out of the barrel. Did you use a test tank?

You should probably get a Factory Service Manual,
so you're not turning screws that you don't know
what they do.
 
I never used it with the 70 on it this was the previous owner. I'm going from youtube videos seeing the speed an evinrude 25 will do.

We run it today in a large bin with a constant flow of water running to it.

I've been watching vidoes of carb rebuilds/set up ect online, there are only a couple of adjustments that can be made.
 
There is no high speed mixture needle.-----High speed is a fixed jet.----------The knob at the top is for the low speed mixture !
 
Several things you need to do first. Adjust the slow needle on the water in forward gear for the highest possible rpms at slow speed. Try different trim angles and load distribution for the best possible high speed rpms and check is around 5000 rpms at WOT. You may need to change pitch size of the prop to gain max performance. Is the cavitation plate level with the bottom of the boat or slightly above? I would think you could not get much more than 20MPH with that setup on a good day in fair weather. Whats the model number of the engine?
 
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Tell us again, how big is that boat? I must be reading it wrong if I am seeing 13+ M. But anyhow, you said it is revving up but the boat isn't going. If that is true, then you have a spun prop hub, or the prop is ventilating. Is the shaft length compatible with the transom height?

If it isn't that, then check to see if it is running on both cylinders. But it wouldn't be revving very high if it isn't.
 
the boat is a Eurosport 13 it's 4 meters basically a dory I've been told with a cathedral hull.. As i said this is all new to me so I'm unsure if the engine is correct for the boat it is just an engine that's been in storage for a number of years.. I've made some adjustments and the weather hear is looking good today so I'll get the boat in the water this afternoon. I'll take and add some pic's later of boat and engine

Thanks all..
IMG_0481.jpg
 
The high speed jet is in the bottom of the float bowl.-----See the brass fitting with the primer feed hose just below the numbers ?----It is deep inside there and not adjustable.----------The one in the front is not adjustable.---The one on the side is a low speed mixture adjustment.-------Suggest you find a manual.
 
The jet in the front top over the large hole is the intermediate fixed air jet and it must be tight. The needle on side is the idle fuel jet. Turn it in clockwise to lightly seated and then back out 1 1/2 turns preadjust. On the water in forward gear after the engine is fully warmed up slowly turn it in 1/8 turn at a time until the engine stumbles and back out for a nice smooth idle. Wait about five seconds between adjustments. Then quickly go from slow to fast, if the engine hesitates ad 1/8 counterclockwise on the slow needle at a time until you get a sice smooth hole shot. Then find the best tilt position where the bow of the boat lifts up and then quickly levels off once the boat hits a level plane plane. If you do not have a tach maybe you can borrow a tach timing light from your local auto part store. Find out the max wide open throttle rpms and get back with us with the results.
 
Dose anyone have any info on the model number?

Update of the engine.. got the boat back in the water yesterday and its running a lot better covered around 20 miles on WOT without any problems and a lot more speed.. i adjusted the manual trim tried it on a couple of different pin locations and found its going best with the motor trimmed in to its 1st pin hole. adjustments i made to the engine are allowing it to run and tick over a lot better..

The prop on my motor is not in the best of conditions so next question was are any other props interchangeable with the evinrude 25hp? am i able to enlarge the prop size or pitch to increase output or efficiency? has anyone done this before or have an idea or witch prop is best for this motor..


Thanks all for your help..
 
I retired in 1991 and your engine is a later model. I'll name whatever I can and depend on other members to fill in the blanks (? marks).

BE25SRETS

B = Manufactured in Belgium
E = Evinrude
25 = Horsepower
S = (?)
R = Rope starting
E = 9
T = 3 (The above 9 and this 3 are combined to be 93 (1993 Model)
S = The factory run marking.... Of no consequence.

 
kimcrwbr1 said:
I am seeing SR is sailboat rope start without tilt but hat dont match his description on what he has pics will help.
Click to expand...

Kim... I was thinking that "S" could possible stand for "Shortshaft"?... but in the book (graphics), yeah, it favors the "Sailboat" explanation.

Also..... My books go as far as 1992, and in checking, the 25hp model that has a "S" in the model number along with an "R" lists the "R" first such as.... BE25RSETS.
 
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Get a timing light tach and test the WOT rpms and change the prop pitch if necessary figure 200 rpms for every 1 inch of prop pitch. I am seeing 5000 WOT rpms around here you can borrow a tach/timing light at any auto part store.
 
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I am going to fit a tach this week hopefully and take the boat out again at the weekend as suppose to be nice weather. Will a car tacho work? Should be for a four cylinder engine but I have one here, not sure if its worth the time trying to fit it
 
I don't believe an automotive tach will work. You could get something like this tiny Tach to measure RPM: https://tinytach.com/gasoline-tinytach

So, if this is a sailboat engine, would that mean it has an extra long shaft? Just asking because I'm not certain. Usually short shaft is 20" and long shaft is 25". However, I've seen some sailboats with kicker motors that seemed to have mid-sections much longer than a typical 25" shaft.

Antjacobs, what is the position of your cavitation plate in relation to the bottom of the transom? If the shaft of your engine is too long it could be your prop is setting too far below the transom and causing you to plow water. This excess drag will definitely hinder boat performance. A 25HP engine should be able to push a 4m boat pretty well, but if the shaft is too long you won't see optimum performance.

KJ
 
Timing light/tach all you do is set it at 2 stroke if not you just divide the rpm by two. A four stroke has two revolutions per spark. Your just using the #1 plug wire to put the inductor on.
 
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