Another Mercruiser 165 bites the dust

[H@ystack]

I have a 1988 Mercruiser 165 3/7 L engine. I've posted here a few times about some minor issues and just looking for some tips. We finally get all the parts up and running, and after some massive shaking and no horsepower to accelerate, I find out today that the 4th chamber has no compression whatsoever.

Seems that our options here are:

- Sell the boat for probably less than $1000
- Get a bobtail tossed in there and keep things going
-or work towards repairs


Just wanting to open discussion here for my thought process.

The biggest cons to sell the boat, is that I don't want payments on another boat, and I don't want to spend and lose money on another boat that may have the exact same problems.

The biggest con to repair it, is I may toss money in to this only to find eventually there are no parts available, massive corrosion, etc etc. So suddenly, I've tossed $600 working towards something that just needs a new engine.

So, I'm leaning towards a bobtail. My mechanic has done 3 this year. Other than the money aspect, I can't find the downside here.

Just opening up for thoughts. I didn't learn about how crappy this engine was from this company until after I bought it. I didn't know it was the black sheep of the family.

 

[GA_Boater]

The 165 GM I6 is a great motor. The 165 470 I4 isn't. If you go for the swap, avoid throwing a 470 back in.

 

[Bondo]

Ayuh,..... If ya go bobtail, go with the 4.3l, rather than another 470,....

 

[H@ystack]

The 165 GM I6 is a great motor. The 165 470 I4 isn't. If you go for the swap, avoid throwing a 470 back in.

Even on brand new, these are still an issue?

Since I've had the boat, I read a lot, and it seems the year I had was just awful. This carried over in to other years too, huh?

 

[GA_Boater]

All 470s are problematic. Later years night be better, but if you find a 470 donor boat or another 470, who knows what shape it's really in.

I think the right year 4.3 is almost a drop in. You need a Y-pipe and need to build side motor mounts. The ratio is the same for 470 and 4.3 motors. Am I right on this Bondo ?

 

[Bondo]

Even on brand new,

Ayuh,... There ain't no Brand New 470s,... They quit makin' 'em well over a decade ago,...

Rebuilt is the best yer gonna find,....

Yes Don, yer absolutely Right,....

 

[H@ystack]

Ayuh,... There ain't no Brand New 470s,... They quit makin' 'em well over a decade ago,...

Rebuilt is the best yer gonna find,....

Yes Don, yer absolutely Right,....

OK.
My guy is putting in a brand new engine. I didn't think it was a direct replacement of the older model. he did say there are a few things he needs to rework to get everything to match up. That's what he is waiting on now. He is working on those specs right now and calling me back.

 

[stonyloam]

OK, ya probably have a blown head gasket in #4 or maybe some coolant getting in there from a bad exhaust elbow gasket. What does the plug insulator look like? If it s pure white then you are getting coolant in the cylinder. Mine was doing the exact same thing, turns out it was a bad exhaust valve from the coolant . So what to do? Were it me (and it was) I would pull the head and see what is going on. If just a head gasket, should be able to get it going again for a couple of hundred bucks. I took mine to a shop and had the head checked, valve, valve job and hardened exhaust seats, and the total for the whole job (including the head gasket) was about five hundred. Book says to remove the intake and exhaust manifolds before pulling, but don't see any reason that you can not pull it all together. It is kind of clumsy and heavy but two guys could do it. Then disassemble on the bench. Make sure you keep track of which holes the pushrods come out of. Yeah they can be a pain, but I did mine 9 years ago and it is still running great. Good luck.
P.s. Use a OEM Mercruiser head gasket.

 

[stonyloam]

Ayuh,... There ain't no Brand New 470s,... They quit makin' 'em well over a decade ago,......

Where have you been Bondo? They stopped making them almost THREE DECADES AGO! Auyh.... time flies LOL!

 

[Bondo]

Where have you been Bondo? They stopped making them almost THREE DECADES AGO! Auyh.... time flies LOL!

Ayuh,.... 'n it goes a 'ell of alot Faster, the older ya get,.......

I'm at the point of lookin' at my "Projects", 'n decidin' which ones there just ain't gonna be enough time for,....
So I'm gonna sell 'em, or scrap 'em,......

 

[nola mike]

Even with a rebuild, you might not be too much if any more in the hole than with a similar 4.3. If I was going to go that route, I'd want a newer fuel injected model and at least get some more power/fuel efficiency for the weight penalty. But I agree with Terry--see if this is a simple fix first. I've been wondering myself whether I'm better off with a rebuild when it comes time, and a redo of the interior v. just selling the boat. Since I'd buy another used boat, who knows what problems you're buying.

 

[Pocket Change]

I love the merc 3.7L. I have had one for 21 years in an 18 foot 1988 Galexy. Got over 3500 hours on it since 1994 when I bought it used. I put a Wagner Electric alternator kit on and electronic ignition. I'm on the 4th exhaust elbow. What sold me was full fresh water cooling. The boat is in Florida for 3 months each winter. No worry about the salt water there. Anti freeze in the engine and manifold. Just rebuilt the carburator for the second time. Also replaced all the hoses this spring. They were all original. Did the seals on the cam behind the water pump in 2002. No trouble since.

 

[H@ystack]

OK, ya probably have a blown head gasket in #4 or maybe some coolant getting in there from a bad exhaust elbow gasket. What does the plug insulator look like? If it s pure white then you are getting coolant in the cylinder. Mine was doing the exact same thing, turns out it was a bad exhaust valve from the coolant . So what to do? Were it me (and it was) I would pull the head and see what is going on. If just a head gasket, should be able to get it going again for a couple of hundred bucks. I took mine to a shop and had the head checked, valve, valve job and hardened exhaust seats, and the total for the whole job (including the head gasket) was about five hundred. Book says to remove the intake and exhaust manifolds before pulling, but don't see any reason that you can not pull it all together. It is kind of clumsy and heavy but two guys could do it. Then disassemble on the bench. Make sure you keep track of which holes the pushrods come out of. Yeah they can be a pain, but I did mine 9 years ago and it is still running great. Good luck.
P.s. Use a OEM Mercruiser head gasket.

So can you help me understand this. This guy thinks pulling it apart is a bad idea. He says "we could get $700 deep into this and suddenly, we find more trouble, can't get parts, and find trouble in the lower area" . He's always been overly fair and completely honest with me everywhere else. Sounds like I need to try elsewhere though. I don't know if I'm comfortable on engine work. I can lay some flooring or change some oil, but that's getting out of my comfort zone

 

[thumpar]

Ayuh,..... If ya go bobtail, go with the 4.3l, rather than another 470,....

+1000

 

[Benny67]

uhh...what's a "bobtail" ? I assume it's a term for repower?

 

[Benny67]

oh...as far as this 3.7 goes, I would pull the head myself and see what's the story before condemning it to death....if it's a bad valve then it's an easy fix if you do it yourself. if you can change the oil on your boat you can do a valve if you take the time,read up on others who have done it and don't let yourself get intimidated by the job.

I got 2 of these 3.7's (mercruiser) in my boat and they seem pretty solid so far with 600 hours on them...sound good ,idle well, run cool and have decent oil pressure and always start (knock wood) my port engine smokes a touch when you start it after it sits for a few days but it burns off in seconds...I would believe it's in need of a new valve seal. but other than that I like the engine(s)

 

[H@ystack]

oh...as far as this 3.7 goes, I would pull the head myself and see what's the story before condemning it to death....if it's a bad valve then it's an easy fix if you do it yourself. if you can change the oil on your boat you can do a valve if you take the time,read up on others who have done it and don't let yourself get intimidated by the job.

I got 2 of these 3.7's (mercruiser) in my boat and they seem pretty solid so far with 600 hours on them...sound good ,idle well, run cool and have decent oil pressure and always start (knock wood) my port engine smokes a touch when you start it after it sits for a few days but it burns off in seconds...I would believe it's in need of a new valve seal. but other than that I like the engine(s)

Thanks for the reassurance.

I actually am starting to think like you are saying here.....I jumped pretty quick to killing the engine vs. looking in to it. We were really advised not to go that route because of the "age of the engine and the possibility of what COULD be wrong"

I think if they do the work, it could be cost for nothing. But, if I learn how to do the work, that's free labor and can at least get a diagnosis....at least that's what I'm understanding.

Im thinking if it is in-fact already dead, what's the harm in me taking it apart. Worst case scenario, I learn something.

(like I learned how my torque wrench broke this weekend and didn't "give" when it reached specs, and I torqued the bejesus out of a bolt )

 

[stonyloam]

First thing, pull that #4 plug and take a look. Don't worry about parts, everything is available new or used on eBay. The lower end is pretty strong, don't see too many problems there. You should be able to pull the head. Intake manifold should come off pretty early, if the exhaust looks problematic (rust), leave it, and pull the head with it on. Ya got all winter and pulling the head should not cost a thing. Good luck.

 

[nola mike]

And, just as important, at this point you/mechanic are treating the engine as junk. So you really can't end up in a worse position than you're in, right? But really, you're not going to break anything by pulling the head. Worst case, you pay someone to put it back together, or you confirm that your engine is trashed or whatever. I'd pull the valve cover first and see if there's anything obvious there, then if not proceed to head removal.

 

[Benny67]

Before you pull the head go to Amazon and get a $27.00 borescope and shove it down the spark plug hole and see what's up. If there is severe damage you can find out immediately. I just bought one and it's the best $27.00 I have spent in a long time. I'd post the link but I think it's against the rules.