My brother has an old early 60's Thompson Searay (I think that's the model), with a marine Iron Duke 4 cyl. Motor is on an engine stand, and when we drained the oil today, it smelled like gas. He's wondering what it might cost for a rebuild kit, so I told him I'd ask around. The FHC DIY room came to mind first. We were quoted over $2000 for a rebuilt replacement.
Does it have an manual fuel pump mounted on the block? This was the common fuel in the sump issue that I recall with the iron duck's(sorry). The iron dukes were tough lil buggers. Could be fine if the compression is good?
Ok, so maybe not such a big deal. Thought I took a pic of the fuel pump, but yeah, it's mechanical. Didn't pay attention how it might be driven. Best way to get compression test if on a stand?
You'd need to rig up a stArter and crank it over to see compression. If it wasn't run long with diluted oil it may be ok. It's not like a car that runs every day. I guess you can do a leak down test also.
Is it possible to put the flywheel back on and put it back on the stand in order to rig up a starter?
You can always do a cylinder leak down test as well. You don't need a starter for that one. I think Advance Auto or AutoZone will loan you a tester for free too. Neither the compression or leak down test will tell you if there are bad bearings in the bottom end but if the engine has compression, I would fix the fuel leak and run it on the stand if at all possible.
I agree, After you fix the fuel issue and change the oil, I'd try to Run it for a bit. I wouldn't throw 2K at it just yet!
Well, $2000 won't be put into it, that's pretty certain at this point. He's been asking how much I think a rebuild would cost if we did it. I suggested around $500 for a kit, plus or minus a few bucks. He'd need to buy a few tools as well. We plan to pull the pan to replace the leaky gasket, and while it's off, see if I can see any problems with the bores. Most of the bolt-ons will be replaced with new. Is it ok to pull the caps and check the bearings w/o tearing the motor down completely? We've considered doing a rebuild as a winter project, and although it could be fun, I'm not sure I want to. I'm going to suggest he get his hands on a manual, if possible.
Thanks nate. Now, to find a manual with that info. That can be my brother's job, as soon as I tell him.
Also I wanted to mention that a gas smell in the oil isn't abnormal. In the old days with manual chokes it was pretty common. A carb running rich could do it as well, or if the motor doesn't get good and hot the normal oil vapors and moisture will collect too. I wouldn't worry too much about it unless the oil level has been going up (meaning the sump is filling with quite a bit of gas) I looked it up in Alldata just under a 2.5L auto engine (I'm 99% sure it's the same aside from cooling and exhaust manifold to the MercCruiser 2.5) The main bearing caps are 80 ft/lbs Big end rod caps are 33 ft/lbs Hope that helps. It's been many years since I've torn down a 2.5 but they are easy to work on and simple. Used in Jeeps, GMs, forklifts, boats, postal trucks, etc!
I thought (could be wrong) that the GM 4 banger blocks (used by Mercruiser) from that vintage were actually 3 liter displacement, but the block was based on the 153 CI auto block. A friend used to have a mid 70s Checkmate with a 3.0 Mercruiser. Not sure if that is what you have or if the specs are different. I don't know much about boats other than what my friends that have them tell me - they're holes in water that you throw money in. Edit - just googled and it looks like there is a 2.5 L Mercruiser as well as the 3.0 I was thinking of, but they're based off the Chevy 4 cylinder 153 CI block, not the Pontiac iron duke 2.5L 151 CI block. Edit again - guess there are also some Pontiac 151 based marine blocks also. Since I'm proving I know jack about boats, I guess I'll step aside and stop confusing the situation.
Iron duke is a 151cu in. 153 cu in is also a GM built motor but not the same. The specs I gave were for the iron duke. I don't have any books for the 153. Used mostly in the 60s-70s, I think before the 151 came out.
If we end up tearing it apart, I can get #'s from the internal parts that may help tell a more complete story. Not sure that's gonna' happen though. There IS a 3.0 as well in the later years according to info I've found. Keep the info coming, it's all gooder.
