1976 18cc with 1984 140 hp evinrude?

[tjspei]

Hi

First post here so thanks for all of the great info I have already picked up browsing around. I just found out I blew my motor and i need to get something put on my 18 before the stripers show up. Does anyone have an opinion on an older(1984) v4 140 hp evinrude. I found one that almost looks new and has been well cared for with a price that will allow me to make other upgrades on my boat and from what I have been reading on repowers for the 18 sounds like what I want at about 300lbs.

Thanks
Tim

[fdheld34]

Welcome!!!
I am running a 1988 140 Johnson looper on my 20 Sceptre and after I redid carbs and waterpump it runs great...
ran a 135 on my 20 Seafari and a 125 on my 18 SF....all did fine.
140 plenty for your 18.
Check compression/carbs etc on the 1984 motor and you will be fine....easy to work on etc.
Also post pictures of your 18 !!
-Fred

[DonV]

I think the OMC 140 looper came out in 1985 which was rated at the prop, yours is probably a "cross fire"? In any case you should be fine! Good luck!

[Bushwacker]

If it's the older cross-flow version, those are simple lightweight motors, but I think they got the old 135's up to 140 hp by moving the rings closer to the top of the piston, which makes for a pretty thin top land. Definitely check the compression before you buy it. Don't think it will tolerate any detonation, so I'd be sure to run premium fuel, decarb it fairly often and don't put too big a prop on it! If it'll rev to at least 5500, you should be ok.

[tjspei]

Thank you for the replies. What should the compression be? I am going to check out the motor this weekend.

Tim

[Bushwacker]

Originally Posted by tjspei

Thank you for the replies. What should the compression be? I am going to check out the motor this weekend.

Tim

I'd say about 115 psi or more if cranked with the throttle wide open, but what's more important is the variation between cylinders. I think my old '75 115 Evinrude generally checked between 115 and 130. The smaller the variation, the smoother the engine will run. Variation should generally not exceed 10%.

[Blue_Heron]

Originally Posted by Bushwacker

Variation should generally not exceed 10%.

Denny is right about the variation between cylinders being the main concern, but I'd be happier with 5% or less. That's not unusual for an engine in good condition. I recently bought 215Robert's '79 Merc 140 Tower of Power and all cylinders checked between 120 and 125.
Dave

[eggsuckindog]

As Denny said it must be propped correctly and yes De-carbs are the most important item for long life on OMC's.

Use Dunks Method(google) which is basically warm it up good - disconnect the fuel line and stick in a can- use 3/4 gal of gas and 1 can of Seafoam - run for 15min and let sit 15-run15 let sit until mixture is gone. Because you have carbs you can also spray Deep Creep in the carbs (same stuff) same run cycle, I did it on my 90 and it worked fine but this very very important.

That HP is perfect for an 18, not sure on the need for prem fuel, when I got my mid 80's 90 my OMC guru said mid grade but not Prem

[tjspei]

Thanks to all for the replies and advice. The motor I went to see was not as advertised but I found one today that was maybe even better than advertised. 140 hp 90s evinrude that compression tested 125lb each give or take a pound. Whole engine looks real clean and it fired up in a split second. Going to drop it off tomorrow to be mounted up.

Now, what prop would you suggest?

Tim

[eggsuckindog]

a 17 Stilletto, works on mine but a V4 might need a 15, they are tough to swing but work great, if it was a V6 150 the 17 would work

not sure you'll find a used one like that but the new ones are under 300 new on the net

I found a used for one DonV and his 23 and hope bought it so we could get a read on a 23

ken at prop gods is very good as this with 140 will be bit different