1986 Evinrude 25hp upgrade info

model # E25RCDC
1648 alumacraft (1987)
side console
rear deck, full front deck (all the way to the console, like a bass boat) (alum frame/top)
3 blade alum prop with some small dings
cranking compression is ~112 on lower cyl ~115 on top cyl.

25mph with 1 other person, no deck, just icechest & gear. no tach @ that time.
23mph with about 360lbs of people, 6gal of gas, no water in livewell or ice chest. ~4600rpm iirc
455lbs of people, 12gal of gas, ice & fish, bait in livewell, little extra gear... it struggled BIG time.
at times 14mph @ 3600rpm to 16mph @ 3800. it did get to 19mph @ around 4200 with the engine cover off for just a little while (throttle blade wasnt 100% open). boat no longer wanted to stay on plane unless it was wot.
got it back up to 22mph with 275lbs less of person with the cover off, 20 with it on.

i read over this thread: https://www.tinboats.net/forum/viewtopic.php?f=4&t=23898

I wanted to make sure that my engine would accept the 30/35hp carb & intake.
with the extra power and a SS prop, i think it will get the speed back.

Thanks guys!

started out as: https://smg.photobucket.com/user/DEER_HUNTER132/media/16ft%20Alumacraft/DSC05331_zps836ee31a.jpg.html

now it has carpet on the alum deck with while hatches: https://smg.photobucket.com/user/DEER_HUNTER132/media/16ft%20Alumacraft/deck_zps20116bf2.jpg.html

Found the engine needed to be trimmed out further. ran much better with a little less weight than before. turned 5k @ 25mph WOT.

now i have my 30/35 carb and intake.
fighting the flat head countersunk screw in the intake on my engine.

I need the fuel line/vacuum line pictures... BAD. i dont know what needs to go where. when i bought this boat they had it all messed up looking. i made it work. but i want it to be right.
pictures will be most appreciated!

do i need to swap the carb bowls?

This is the best pics I could find in a hurry

The 25 bowl has the nipple for fuel feed to the primer, can i just swap the nipple in place of the plug?

Got a picture to describe what you mean?

The primer pulls fuel out of the bowl and will push it into the intake and backside of the carb

[url=https://www.tinboats.net/forum/viewtopic.php?p=334013#p334013 said:

Johny25 » 08 Nov 2013, 20:51[/url]"]Got a picture to describe what you mean?

The primer pulls fuel out of the bowl and will push it into the intake and backside of the carb

Click to expand...

Thank you. i got all the lines figured out after many hours of research today.

for future reference:
oil hose goes from the lower crankcase to the upper crankcase below the flywheel behind the carb linkage where it attaches the the intake. this equalizes the oil that is trapped in the engine that gravity causes to drip the the bottom crankcase.

the plug in my 30hp carb gets replaced with my factory 25 nipple, that attaches to the outer nipple on the primer.

the inner primer nipple has a hose attached to a T, which goes to the nipple on the intake and top of the carb in the back.

my engine had the primer hose just shooting the fuel @ the throttle plate. the hose was attached the intake and carb alone, which is not correct.


What i need answered:
why does the side of the 30hp carb have a screen in the round port where my 25 has a plug? (near throttle linkage)
do i adjust the idle fuel with the flat headed needle valve in the brass tube (near the rear upper nipple)?
what is the hole in what looks like a orifice where the 25hp idle needle valve goes?
i will post pics of what i mean shortly.

Click for super size HD pictures

The screen covers the entrance to a bowl vent.
The "hole" in the front of the carb in the second photo is where the idle air bleed is located. That carb no longer uses the adjustable idle mixture screw.

thank you.

i took the boat out, man it ran much better.
it was simple to get the idle mix set, idles low and steady, now i can troll without spitting and sputtering missfire sounds.

i only had two "problems"
after a wot run, i back down on the throttle for a no wake zone. slow or fast throttle movement didnt matter; it would start running rough.
all i had to do was quickly wot the throttle then back to idle two times and it idled smooth after that.

2nd issue, it didnt rpm or run any faster. i tried trim out and in, no top speed change.
5000rpm (5500 max with the 30hp) is all it would do @ 25mph. thats all it ran before i put the decking in.
it has the stock alum prop.

So you are running 25mph with the decking in now and you ran 25mph without it in before? I noticed you did not have a tach reading on your original run of 25mph so how would you know if you had a reading change?

I am not sure how much your boat weighs but 5-10hp gain will be more noticeable on lighter setups. A 35hp motor will have the same performance as a 25hp on a pontoon, basically is what I am saying

[url=https://www.tinboats.net/forum/viewtopic.php?p=334202#p334202 said:

Johny25 » 11 Nov 2013, 17:48[/url]"]So you are running 25mph with the decking in now and you ran 25mph without it in before? I noticed you did not have a tach reading on your original run of 25mph so how would you know if you had a reading change?

I am not sure how much your boat weighs but 5-10hp gain will be more noticeable on lighter setups. A 35hp motor will have the same performance as a 25hp on a pontoon, basically is what I am saying

Click to expand...

25hp, 25mph @ 5000 with decking + 200lb passenger.
30hp, 25mph @ 5000 with decking, no passenger.

the decking isnt super heavy, but its for sure the weight of an adult male total. i also have 2 batteries, 12gal tank. stuff adds up QUICK.

video of the 30hp carb test run:

Well I couldn't watch the video but something does not seem correct obviously. The numbers are worse than the 25hp if I am reading it correctly. Your pushing more air and more fuel theoretically so you should see a change of some sort here in the other direction. Are you sure the link and sync is correct?

What is the current pitch on your prop, I am curious?

[url=https://www.tinboats.net/forum/viewtopic.php?p=334243#p334243 said:

Johny25 » 12 Nov 2013, 02:39[/url]"]Well I couldn't watch the video but something does not seem correct obviously. The numbers are worse than the 25hp if I am reading it correctly. Your pushing more air and more fuel theoretically so you should see a change of some sort here in the other direction. Are you sure the link and sync is correct?

What is the current pitch on your prop, I am curious?

Click to expand...

i didnt reset the link n sync on the new carb, seemed close so i let it ride.
is the total timing advance different with the 30hp carb?
i think i had it set to 26* going off the flat surface of the starter bracket.

no idea what pitch prop is on it, stock aluminum is the best i can tell.