New motor, new issues.

[Shadow91]

Okay, got a new (used) 2.5 OMC engine this weekend and got it installed and ready to go yesterday. Took it to the lake to see how everything was and for the most part it runs fantastic. just a few issues I need to get sorted out which hopefully i can get pointed the right direction here.

To start off with I HAD a 252FTHRCTR originally that had a cracked block. Swapped it with another 2.5 engine and kept the enclosed cooling system off the new engine. That paired to a 400 series stringer stern drive.

First off, engine temp stayed at 180* the entire time, I assume with an enclosed system that would be correct. Just wanna double check. Also, is it smart to stay with the closed system or go back to just raw water cooling? The boat will never see salt water and will only be used to pull tubes/knee boards.

Second issue is it seems as if the drive is disengaging from time to time. Like itll run great in a straight line, however if i try and take faster turns or quick u turns i feel the engine spool up like its not in gear for a second. No hard thump or shock, just RPM free spin it seems.

Then last issue is, fired up and ran great, punch throttle and itll shoot up to about 42-4500 rpms and just take off. Well after between a minute to 10 minutes itll almost choke up and the rpms will drop to about 3500. I can back off the throttle for a few minutes then punch it again and itll take off back above 4000, again for only a few moment. It seems to get better and better the more the engine ran but not sure. It also wants to almost die when taking quick turns. Ill lose all momentum going into a sharp turn and the engine just drops to 1500-2000rpms. Im assuming this is all carb issues and a simple rebuild and tune will do away with that. As well as new plugs/wires/cap/rotor/points/condenser (all brand new on the old engine)

Thanks again guys!

Original post
http://forums.iboats.com/forum/engi...oard-engines-outdrives/10457919-motor-options

 

[Scott Danforth]

I would have a MOD merge the threads or you should provide a link to your other threads so people know the whole story

regarding the 180 - yes, its because you have a heat exchanger on it.

regarding the disengaging. if its not your prop ventilating or the prop hub slipping, its the splines on the vertical driveshaft letting loose. that will require you to rebuild your upper gear box.

regarding the running and loosing power. most likely fuel system related. either crud in your new to you carb on your new to you motor or crud in your tank that your pumping into your new to you carb. loosing power in turns sounds like carb/float issues.

 

[Shadow91]

It feels to me like the prop is just spinning air for a second until it catches water, but i wasnt sure if that was an actual thing that happens.

And I figure id start with a new fuel filter and rebuild the carb and go from there with the run-ability issues.

Also, i think I may have gotten a 3.0 from the pictures i see online of the manifold. How exactly can I tell? I know ill need that info for when I eventually need more parts.

 

[Scott Danforth]

if your simply ventilating the prop in the corners, trim down a bit

look on the side of the block. it will be either 153 or 2.5 for the 120 hp or it will be 181 or 3.0 for the 140 (I cant remember if its liters or cubic inches).

 

[Shadow91]

So the only numbers on the engine are 2770087 53 89

Also, the end cap on my heat exchanger is leaking. Has just an age crack in it that lets some water pass it. Trying to find a replacement but everything I can find shows like a flat steel piece and a rubber one with a hole in the center for a bolt. Mine are capped and held on by a hose clamp. Any idea where to get new caps?

This is what it looks like

 

[Shadow91]

Well I believe I have a harmonic balancer (it's pressed on with no bolts, vs my old 2.5 has a bolt on pulley) and the manifold matches every 3.0 I can find. I see the 2770087 is just a casting number for the bare block used both on the 2.5 and 3.0 so that's useless.

I'll also say I get about 700 more rpms from this engine and the boat is definitely faster, so I'm just gonna assume it's a 3.0

 

[Scott Danforth]

is that a 4" cap (actually 4-1/8). look up crusader 22094. 4" HX clamp on cap.

 

[Shadow91]

Holy crap, any particular reason they're $100 apiece??

 

[Scott Danforth]

because its a crusader only piece and is no longer current production. hence the reason most other heat exchangers have the spider casting and the flat end cap.

if you know someone with a lathe, make a cap out of Naval Brass, 4-1/8" diameter, about 3/4" thick. have them machine a hose retention groove on it. then a 2" piece of exhaust hose and two hose-clamps could be used.

 

[kenny nunez]

There may be a rubber cap either @ Mac Master -Carr on line or Home Depot & Lowes. Graininger or a plumbing supply house, possible source.

 

[Scott Danforth]

nothing on McMaster or any other sources I could find. When I worked at Champ, we custom made a few copper caps out of a custom stamped end sheet and a section of 4" shell material and put a bead on them for customers to use a bit of 4" hose and two end caps. I think we charged $75 for the custom end cap back in about 2009.

 

[Shadow91]

Well ended up pulling the enclosed system due to finding out it had a crack in the heat exchanger as well.

Converted it all back to just regular raw water cooling and ran it hard this weekend. Rebuilt the carb and got it tuned and adjusted fairly well. Engine temp stayed at about 170 according to my gauge the whole time and idled and pulled fantastic.

Thanks for all the help guys. Really helped me give this boat another chance. And I've learned a ton.