165 Merc engine swap???

[jtackett@ipa.net]

Hello all, My name is Jeff & I'm new here. From what I've read so far this a great site, I did a few searches & found out all kinds of info.! My question is this: I have an '80 Caravelle 165 Merc that's getting water in the oil. I pretty much know what I'll have to do to fix that but my question is can I put a Chevy 292 in without modifications? From what little I've been able to find out I think I can. I NEED more umph but don't want a v8 or another boat. Any input would be greatly appreciated! Thanks in advance...

 

[Fouled Plug]

Re: 165 Merc engine swap???

Is the 292 swap worth the extra effort? It might gain around 10 horses or so but would need a some of modification to be a marine motor. I think the 292 block is around 1.5 inches taller, which may be an issue with exhaust, mounts, etc. If the 165 isn't too tired, let's take a look at the water ingestion problem. Have you taken the compression readings yet?

 

[jtackett@ipa.net]

Re: 165 Merc engine swap???

From what I've been told, and it may be wrong of course- that's why I'm trying to find out, the 292 is the same block other than the bore. I just thought if it was the same it would be an easy swap. Maybe not! I haven't taken any readings yet but I also have a crack in the outer water jacket (from a couple of years ago on a freak cold snap) that comes into play. Would I be better off leaving the 250 in & doing some work to it for more hp? What do you think....Jeff

 

[Fouled Plug]

Re: 165 Merc engine swap???

If the compression is good on the 165, and the crack is in a repairable spot, I'd say fix it! What size boat is this beast in? Maybe someone else has more inline-six knowledge, but I still think there's a difference between the 250/292. Might just be in my mind, though!

 

[ODDD1]

Re: 165 Merc engine swap???

Mr T merc actually did use the 292 CID motor in boats....I think they called it a 200 [hp]I only saw a couple of them many years ago...I dont think anything swaps between the 2 motors, except the bell housing pattern....the 165 is a tough motor, maybe worth repairing?

 

[jtackett@ipa.net]

Re: 165 Merc engine swap???

The motor's in a 17' walk thru/v-hull. The boat is VERY heavy. When I got the boat it had a 3 blade 19 pitch on it & had a hard time pulling skiers (top end about 43). I put a 4 blade 13 pitch on & it would yank your arms out of their sockets! I was still under the rated 4300 rpm wot so that was good. Now I'm back to having trouble pulling skiers again. I guess I'll have to check the compression first off & go from there. The crack is in a pretty good spot to fix, I used some Quick Steel & that worked pretty good though I had to hook up an automatic bilge to get the water out on it's own (still leaks, but not like the flood when it first cracked). Nobody around here knows much about the 6 other than to say take it out & rebuild it. The 292 may not work but I'd like to know for sure before I rebuild this one. If you come across someone that does knkow the difference, let me know.

 

[rloper]

Re: 165 Merc engine swap???

Hello Jeff,<br /> I have spent a great amount of time working on the old 165 merc. Good engine with lots of torque. First to determine if you have a bad exhaust manifold, it will leak water into the exhaust and you will suck water in on the exhaust stroke and get on the pistons. This water is forced into the oil. Run a compression check, all plugs out. Should run @ 105 +/- 10, if close then hook up hose to the muffs, take the hose of going to the exhaust manifold and let it empty into the hull(have drain plug open)and run engine(after putting in fresh oil and filter). Should stay clear,only run for about 10 min at a time like this to keep from getting the exhaust bellows to hot. 9 out of 10 it will be a bad exhaust manifold. replace it and the Riser. Probably need new exhaust bellows to, usually only get ruffly 4-6 years on one. About the 292 it will not enter change. And if it did it is not worth the trouble. Watch turning that old 250 up to max rpm's for long periods it will not take it. I liked to cruise at no more that 3000 rpms. If it turns out to be the head find an auto head in junk yard, put in new stelite valve seats and brass freeze plugs. Loper

 

[jtackett@ipa.net]

Re: 165 Merc engine swap???

Thanks for the input! It will only turn around 4100 & only if I trim the heck out of it. The main use is for skiing & tubing, when it was running right I was pulling 4 tubes (talk about a lot of fun!!!). I don't get up to 4k very often & when I do it's for VERY short spurts. When you say take the hose off I assume you mean the hose coming from the water pump into the manifold, right? I had the manifold off when I first got the crack & noticed a lot of rust between the ports so it could very well be the manifold is the problem. I hope I can get to it in the next couple of weeks (don't want the boating season to sneak up on me! The bellows are about 3-4 years at this point & didn't see any cracks the last time I checked, but that was the end of last season so I'll check it out closely when it comes that time. Once again, thanks for the help!!! Jeff

 

[DJ]

Re: 165 Merc engine swap???

MrT,<br /><br />Loper's right. The two will not easily swap.<br /><br />He's also right about the rpm. The 165 does NOT like a lot of rpm. 4300 IS TOPS.<br /><br />Took a good look at the engine to make sure it's healthy. Sounds like you've lost some power.<br /><br />If you're going to completely rebuild it-easy. A good machine shop can get you a few more ponies by messaging the intake and exhaust ports. Don't let them shave the head though, except enough to make sure it's flat.<br /><br />The 250 was a strong engine, it just didn't breathe very well.