Offshoreonly.com
Page 1 of 2
1
2
Show 40 post(s) from this thread on one page

Offshoreonly.com (https://www.offshoreonly.com/forums/)
-   General Q & A (https://www.offshoreonly.com/forums/general-q-20/)
-   -   Twin engine question (https://www.offshoreonly.com/forums/general-q/358840-twin-engine-question.html)

boatnt 02-01-2019 10:28 AM
Twin engine question
 
So helping out a buddy with an engine build, he’s got a twin engine boat big block GM EFI engines, hurt one Cylinder in the block so he needs to go 30 over, question is has anybody done this before? one engine stock the other engine 30 over, do they run the same or are they out of sync?Is 30 over enough to notice a difference?

beaver 3 02-01-2019 12:16 PM
there will be no difference.

14 apache 02-01-2019 12:19 PM
Sometimes I will only go bigger on a few cylinders just to save the blocks. If it's just one hole see if it will clean with a .005 piston if they offer it.

f_inscreenname 02-01-2019 12:43 PM
Originally Posted by 14 apache (Post 4670735)
Sometimes I will only go bigger on a few cylinders just to save the blocks. If it's just one hole see if it will clean with a .005 piston if they offer it.
Had a Jasper motor that had 3 different size pistons in it. Really pissed me off trying to do a refresh.

14 apache 02-01-2019 12:54 PM
Originally Posted by f_inscreenname (Post 4670741)
Had a Jasper motor that had 3 different size pistons in it. Really pissed me off trying to do a refresh.
lol ya that would piss me off to. Only reason I do it to save room if it ever fails again. Did one each block had 2 big pistons and 12 small ones piston people made 12 big ones they had to make 8 more small ones.

mggdoors 02-01-2019 01:13 PM
Originally Posted by f_inscreenname (Post 4670741)
Had a Jasper motor that had 3 different size pistons in it. Really pissed me off trying to do a refresh.
mental note to self. Never using jasper

Baja Rooster 02-01-2019 01:56 PM
I know JE makes some pistons that are just a few thousands over stock if a good power hone will clean them up. You’ll never notice any difference with one engine bored over.

ThisIsLivin 02-01-2019 04:44 PM
I bought a boat that sat in storage so long the cylinders rusted so badly the rings wouldn't contact the bores all the way around. I ordered a set of Diamond pistons at 4.565 to clean it up no problem.

14 apache 02-01-2019 05:28 PM
Had a boat with 454 one side and 510 other side ran same rpm on top end. 510 had more mid range.

Rookie 02-01-2019 07:17 PM
I had to pull one of my 550HP 454's last summer and put in a spare Merc 420 I had laying around. There was ~600RPM difference in the engines. A little under 3/4 throttle on the 550HP and the engines were in sync.

You won't notice the difference with 0.030" Put the power steering pump on that engine...


All times are GMT -5. The time now is 08:36 AM.
Page 1 of 2
1
2
Show 40 post(s) from this thread on one page


Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.