1978 Evinrude 140 V4 Only firing on 2 cylinders

[ct1762@gmail.com]

The V-4 crossflow was a staple production engine.---The 100 HP was only offered in 79 and 1980.------All about marketing.-----Same pistons fit a 1974 and 1998 model 115 HP.----I do not understand why the design of top piston ring was not changed.

i have 2 xp100's. 1989 and 1990. interesting motor as its got the ports of a bubbleback, but everything else is an 88/90 hp.

 

[ct1762@gmail.com]

Swapped in new coils and now I am running on all cylinders!

Does anyone have suggestions for good replacement control cables.

did you get new compression readings? hopefully idles well should tell the story but good to know what the true #'s are! im betting 115psi+ if it idles well.

 

[racerone]

The XP 100 was a 115 HP marketed as a 100 HP with " extra performance " i believe.----- It is all about marketing / decals.

 

[ct1762@gmail.com]

The XP 100 was a 115 HP marketed as a 100 HP with " extra performance " i believe.----- It is all about marketing / decals.

it has the same ports as a 110-140hp motor.

 

[jimmbo]

The old Crank rated 140 and 115 had the same porting, and keeping track after the switch to Prop rating is like looking at a bowl of spaghetti.
The Bubbleback did change the Exhaust tuning, whether or not they ever bolted it to the 90hp block, I don't know, but it may have upped the power a bit to provide motors like a 100. OMC also mixed and matched Cylinder Heads in the late 80s and 90s, so you really need all the Parts Manuals to keep track of what made what

 

[ct1762@gmail.com]

The old Crank rated 140 and 115 had the same porting, and keeping track after the switch to Prop rating is like looking at a bowl of spaghetti.
The Bubbleback did change the Exhaust tuning, whether or not they ever bolted it to the 90hp block, I don't know, but it may have upped the power a bit to provide motors like a 100. OMC also mixed and matched Cylinder Heads in the late 80s and 90s, so you really need all the Parts Manuals to keep track of what made what

yea ive had both gt100 and a bubbleback side by side a few times. 100% same porting. Its the exhaust, heads and carbs (1 3/16'') from an 88/90. pretty neat they actually did that, TBH.

 

[jimmbo]

I know that with the Crank rated engines, Porting the 90 block to the 115/140 specs(bigger Holes), and as carb change gave you a 115. To get to the 140 stage, the Heads needed to be changed, the Block machined to accept the Bubble Back, and some rejetting of the carbs(some 140c used larger carbs than the 115, other didn't, I'm still talking crank rated). I don't remember if the Cam that opened the Carbs was different between the various motors as the Primary Pickup often varied between HPs. The 140s sometimes also had the Crankcase Stuffers, to increase the crankcase compression.