1977 EVINRUDE 140HP V4 Rebuild

[LV2FISH4CATS]

Hello,
I found out I bought a bad motor and now it is time to rebuild it. The carbs fouled up and I burned(or the old owner Burned) the # 4 piston. I have decided to rebuild it and to replace all 4 pistons. So I am having it bored .030 + on all cylinders and installing new pistons , wrist pins, and bearings. The real question I have is?? How much difference will there be in Horse Power??? It is the 140 now and my boat is rated for a max of 150HP?? I do not believe there would be any problems?? But thought I would ask? Oh and while I have it apart I am going to do a full lower end rebuild and re-paint the motor. I will post pics of the whole thing when done.

Thanks for any info.

 

[another todd]

Re: 1977 EVINRUDE 140HP V4 Rebuild

Boring the motor 30 thousanths over will not increase your horsepower much if any. You will be fine.

 

[emdsapmgr]

Re: 1977 EVINRUDE 140HP V4 Rebuild

You will use your same carbs after the overhaul. Since you won't be putting any more fuel or air into the engine the hp should not change.

 

[kenmyfam]

Re: 1977 EVINRUDE 140HP V4 Rebuild

No noticeable difference. Good Luck with the rebuild. Looking forward to the photos.

 

[Faztbullet]

Re: 1977 EVINRUDE 140HP V4 Rebuild

Why .030? why not .020? Is this cylinders that damaged or out of round?

 

[wilde1j]

Re: 1977 EVINRUDE 140HP V4 Rebuild

Have the machine shop mic the bores before deciding on oversize, then buy appropriate pistons and ring sets.

 

[LV2FISH4CATS]

Re: 1977 EVINRUDE 140HP V4 Rebuild

Machine shop has checked cylinder and it is going to take .030 piston. The ring broke and scared the wall too. I know everyone has said I can do just one piston, but i decided on all 4 with new wrist pins and bearings. I came across a NEW IN THE BOX old stock head for it and picked it up. I talked with one guy and he said to stay away from WIESCO pistons?? I bought PMC pistons? Is one really better than the other?? He said something about the WIESCO size varied with the same pistons? I am not sure but the machine shop has all 4 pistons and will be boring them for each hole. ANY RECOMMENDATIONS ON THE REBUILD WOULD BE GREAT. I AM STILL LEARNING THE 2 STROKE MOTORS.

THANKS
LARRY

 

[frozenokie]

Re: 1977 EVINRUDE 140HP V4 Rebuild

What I can say about Wiseco's is that I've rebuilt two motors using oversized pistons. An 85hp Merc - all four at 30 over and a 125hp Merc at 20 over. What I noticed was that the compression was considerably higher. Which, in turn, should equate to more torque and a little more horse.

I had 150 PSI on the 85 and 130 PSI on the 125 afterwards. The 125 would plane out my 18' boat in 3-4 seconds and top out at 65mph. And the 85 would plane out a 16' Ranger in about the amse time. Both compared to planing times doubled before rebuilding. In my opinion, it does boost a little horse and torque because the Wiseco pistons are lighter.

The bad side is that they are forged pistons and wont break apart like cast pistons if something goes wrong.

Good luck!!!

 

[frozenokie]

Re: 1977 EVINRUDE 140HP V4 Rebuild

He said something about the WIESCO size varied with the same pistons?

I ran into the same problem on a 125 Merc I purchased. The key to matching pistons to your new bore size is to be triple check your measurements and be sure to use the manufacturer's tolerances on piston-to-cylinder sizing. I found that on some online websites for Mercury parts (pistons in particular) that the piston sizes given for a certain bore were incorrect. SO BE CAREFUL!!!!

 

[LV2FISH4CATS]

Re: 1977 EVINRUDE 140HP V4 Rebuild

Thanks Okie,

I live in Colorado but have a place in Grove and spend my boating time on GrandLake. Love to boat and fish that lake. Never seem to run out of room. I will be running the fresh rebuild down there next spring. Can Not wait.
Thanks again for the info.

 

[Dhadley]

Re: 1977 EVINRUDE 140HP V4 Rebuild

The Wiseco piston assemblies are not lighter than the equlivent OE piston. If you weigh the piston, rings and wrist pin you'll find they are both within the manufacturers tolerance for weight. PMC went out of business quite a while ago. I'd sure stay away from any of their parts. Make sure the Wiseco pistons are the newer 31 series, not the older 30 series. You'll want the 3173 pistons, not the 3073 or the even older 3013 series.

 

[Solittle]

Re: 1977 EVINRUDE 140HP V4 Rebuild

Why rebuild the gearcase? - - Unless there is water in it change the oil using new gaskets on the fill & drain plugs & be done with it.

 

[LV2FISH4CATS]

Re: 1977 EVINRUDE 140HP V4 Rebuild

Thanks for all the info guys. I have the engine completely apart. The block is on its way to be bored and i have cleaned every inch of the remaining parts. I have started to repaint the whole outside. I bought the Zinc Chromate primer and have cleaned and primed everything. Now I will start to repaint. I could not find the exact color so I am going with a close second. I was wondering if I should shoot it with an automotive clear coat with UV protector in it?? I am excited about doing the rebuild and it has been a lot of fun so far. ( other than cost) ha ha I am sure I will come across a few problems on the way but with the great bunch here on IBOATS it will make the going better. I will start having pictures soon... Thanks again to every one....

P.S. If anyone wants to share the pit falls to avoid when doing a rebuild please let me know...