1955 7.5 hp tank conversion starts runs rough stalls

[BlackoutBill21]

ok, after much searching, Ive finally decided to post... I own a 1955 evinrude fleet twin 7.5 hp 18902D that I've converted to a singe line fuel system.

New coils, plugs wires, confirmed spark, carb (taken apart and cleaned with cleaner / compressed air) . It starts and will run with slow speed needle out like 7 turns, and full throttle but it barely stays running. When i did the conversion I plugged the right side of the intake manifold hole. The video on youtube starts plugging one side then switches to the other side. My first question is does it matter which side you plug?

Second, I installed an inline fuel filter. Could the location be preventing fuel from reaching the carb? Its located after the primer bulb before the connector.

Third, The connector at the motor leaks fuel a little.. Ive been informed that most do.. its an old connector so should i replace it?

Any ideas why the rough idle? barley stays running unless the throttle is full but it will continue to run rough if i do.

side note, I've done extensive research on how to break down this carb however I will note that i didn't buy a new kit or replace and clean out the metal plugs that have to be punched out. I know my luck and highly doubt its something as simple as a clogged jet. But if you buys without a shadow of a doubt tell me its carb related then i will break it down again.

 

[racerone]

The connecter should not leak.-----Is there a filter in the glass fuel bowl ?------7 turns out is way too much.

 

[Crosbyman]

No Title

here is my story on a 7.5...which runs perfectly

​did the usual..necessary things... coils, carb kit, carb clean incl those 3 little drip holes under the dime size plug on the upeer LS chamber ..., etc...


​ On my 5.5 I had no choice but to use the manifold mod on utube....removed the check valves etc... the 5.5 works great all idles all day no issues

​on the 7.5 I went with the OMC square pump over a side cover plate method and plugged the air nipple behind the carb

​as racerone said... no leaks ... if it leaks it can suck air !! just replace the o ring on the female side before chasing a connector

​

 

[racerone]

Nearly 50 years ago 2 fellows marched into the shop with one of those 7.5 hp motors.----------Said--" we can't get the carburetor adjusted right "----------I said just wait and I will save you a trip back.----------Threw it in the test tank and quickly determined that it was NOT a carburetor issue at all.-------The head gasket was blown.--------------That is why I say do all the trouble shooting first !!

 

[BlackoutBill21]

yes the bowl has the filter which looks excellent. I know 7 turns was too much lol but i figured it would help you guys figure out whats going wrong

where does one find those square pumps?? where are the fuel lines to the carb in your photo? Thank you for the reply's gents

 

[oldboat1]

What running shape was it in before you did the fuel conversion? That is, did the motor run well for you at any point?

 

[BlackoutBill21]

No I picked it up not running. When I pulled the fly wheel it had cracked coils, the high speed needle was seized in its port, and when it was running no water was coming out.

 

[kbait]

Your 1st post says it's a 18902D. That's a '69 18hp??

 

[HighTrim]

Step 1 What is your compression readings cold and dry?

Ok, you have good spark, will it jump a 1/4" gap on an inline tester with a bright blue ZAP!!?

When you did the water pump, did you inspect the shock absorber beneath it? Spring could be sprung a bit. Wont allow them to idle at low speed. When real bad wont start at all.

Are you sure you are actually seating the needle, before you start backing it out?

 

[HighTrim]

If all is actually fine, you have a severe air leak somewhere, be it the crankcase, carb, etc... You need to find that leak.

When you say the connector leaks, does it leak when you take the hose fitting off, or leaks while running and attached? Should not leak while the hose fitting is attached. Normal to leak when you take the hose fitting off however. If it is leaking while hose is connected, change your fitting, or change the o ring.

 

[Crosbyman]

No Title

picture shows just the plate .. you need drill a hole centered on the square pump's back pulse port and 2 mounting holes for the bolts

​ pumps available at Sierra and pricier at the BRP dealer Iboats here likely has them to

​only 2 hoses need one to the fuel connector one to the carb pulsing from the crankcase directly to the pump... from behind the pump body

if you want to run 3 hoses you can do a mikuni pump pulsed by the nipple behind the carb

​

 

[Crosbyman]

No Title

by the way if you did the intake manifold mod I read sometime ago that some folks had issues with that approach because the pulse line ends up with crankcase oils

​true or not I do not know since my 7.5 was done with the pump on a plate as pictured above. another method is to drill and tap a cover plate for a threaded nipple to supply a pulse to a mikuni pump as on a qd or fd I did years ago

 

[BlackoutBill21]

no... its an 7.5 hp 1955... the 18 hp is posted on another thread I apologize... its the 7518 motor... the 18902d is for another motor. Ive cant edit my previous post lol.

I will test compression after I test it one more time... I've since re-routed the vacuum cap and bought a new gas connector to see if there is a difference.

needle is absolutely seated. I wont force it cause i know i will damage the needle if i do.

speaking of, yes it leaks gas when connected hence why i bought a new connector. will update asap

I haven't replaced the water pump yet because i never go there until I can verify its running first. No sense in spending money if engine too far gone no? plus i wasn't ready to pull the power head until absolutely necessary. But if that could be an issue with the idling I will tackle that asap as well. I can say that for the few seconds it was running it wasn't pushing water. I will also inspect the shock absorber as well.

If all else fails I will investigate the plate to fuel pump mod you guys are running. Thanks for the pictures! where does one buy that adapted plate cover with the threaded fitting?? I'm currently running the mikuni pump with the three lines

Thank you gents! will update asap.

 

[oldboat1]

Your procedure is backwards re. the water pump. If you are going to try to fire a motor, you have to be sure it's pumping water first. (Costs you a powerhead gasket and an impeller up front.)

 

[BlackoutBill21]

yeah but I get a lot of older motors and the water pumps are getting harder to find.. I figure if it starts up good I'll kill it before i do any damage. Just my opinion but you guys are far more experienced than me So i'll open up my mind and rethink my procedure.

 

[racerone]

Nonsense---The impeller used in the 1955 models also was still instaled in the 1978 model 6 HP.----Used for many years and will be available for a long / long time.----Most good shops will have it in stock.---Ask for it by the part number.--Some places will say NOT available if you ask for parts for a 1955 motor !!!

 

[BlackoutBill21]

yeah for this motor...but, you should see some of the monsters i come across

 

[HighTrim]

I cannot think off hand of an impeller you cannot get, if you know where to ask of course!

There are a couple members of the AOMCI that make the hard to get ones. Simply send them your old hub.

 

[Crosbyman]

No Title

Q. - "where does one buy that adapted plate cover with the threaded fitting?? "



​you simply drill out the cover casting and tap it for the nipple thread size the fitting is available everywhere (autoshops)

​

 

[BlackoutBill21]

Sounds good... after I get a day here in NJ that isn't snowing or raining... I'm gunna give her another test pull with my new fuel connector and changed vacuum cap location. If it still starving, I'll tap the plate and try that!! Very excited Over here!