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Engine repower help

searay57

Contributing Member
"I have a 1978 Searay Seadan B

"I have a 1978 Searay Seadan Bridge with twin mercruiser 255hp 1.5 reduction velvet drive transmisions. engines runs well but after a 20-30min run the oil pressure drops on the engines. starts off at 40pds and goes down to 10-20pds @ idle.

This winter i would like to go through the engines and transmissions. i am looking for something very reliable when it is done (capable of trips of 200-300 miles at a clip) what do you guys think my best bet would be, refresh my engines (rings, pistons gaskets) buy reman engine, or buy new enines. same for trans both work fine, but I have no idea how they have been cared for over the years. i am intersested in all sugestions and experiences with repowers."
 
"Jeff
You have a good looking


"Jeff
You have a good looking boat with a good package as far as the engines and driveline go's.
I think if it was me, I would look at rebuilding rather than replaceing.
I would find someone who I trusted as far as engine building go's and line them up for the task and have the engines built to perform the way I would like them to.
I have just picked up a couple of rebuildable short blocks for $1-00 on ebay and I will rebuild them the way I want, instead of buying an exchange short or longblock that may not have been built with the care or clearances that I desire.

Cheers
Peter C"
 
"10-20 psi @ idle is good when

"10-20 psi @ idle is good when hot. Mercruiser gages acceptable oil pressure at 2000 rpms. They don't care what it has at idle, there is no load on the engine at idle. This is why the alarm sender is set for 5 psi.

You're pushing 30 years old, so I'm not going to discourage you from freshening her up, but I wouldn't cut my season short to do it. That doesn't look like the coast of Florida in the background so I'm sure your season is already short enough.

Good luck
Rick"
 
"Jeff,

Nice boat! I agree w


"Jeff,

Nice boat! I agree with both Rick and Peter 100%. Your pressure looks good. I am not a boat engine expert but have built a couple car motors and 10-20 PSI is okay at idle. I think the frame of reference is at least 10 PSI for every thousand RPM in cars. As long as it's constant. Same when at load for a given RPM. Worries,in cars anyways, is you can get oil starvation on hard curves. really hard on the main bearings. I think the best test you can do is a compression test and vacuum test. I also pull the valve covers to look for sludge and look in the watr passages to see how much crap is in there. If these tests are within spec, move along and enjoy your boat. If not, follow Peter's advice. Just find a good machinist. Maybe using this forum?

Good Luck,
Ken"
 
"i just repowered my 28'we

"i just repowered my 28'wellcraft that had twin mc rwc 305's with new crusader 5.7 power pack specials,these are brand new gm vortec engines and you just add your alt,starter,rwpump tranny and exhaust.i too have 1.52 velvet drives (1987s)that work just fine.engines were 8k for both and the results are incredible.economy,power,and speed all up and reliability -no problems @ 25 hrs.did the work myself and only other major expense was two fwc cooling kits for 1500.otherwise whole job would've been under 9k"
 
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