Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

[Blueghost924]

Hi, I'm new to IBoats and kinda new to boat ownership. I recently bought a 1987 Renken 21' boat that has the 3.7L Mercruiser inboard installed still. From all looks, the block is pretty well intact. The head and valve cover are attached. The intake and exhausts of the head are rusty. Also, the exhaust manifold came with the boat, but was not attached.

My big question is it worth trying to salvage and bring the current engine installed back to life? Or would it be better to just install a re manufactured motor? If I decide to bring the engine back to life, I am going to have to buy, as a minimum, an alternator, spark plugs/wires, distributor, intake manifold and carburetor. To help in the decision, I'm considering trying to turn the motor over and check compression. I'm not sure how to turn it over by hand - is there a way to do this? I'm also considering seeing if the starter/solenoid are good as well. Prior to turning over, I'm also thinking about spraying some of my Seadoo Bombadier spray lube down each spark plug hole. Also, I've checked the oil level, and it's good (although it's probably old).

I would guess that the engine hasn't been run in about a year.

Attached is a picture that shows it's overall condition. Thoughts?View attachment 212532

 

[Bt Doctur]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

looking at that much rust, I`d say that motor is done

 

[Volphin]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

Ugh. The intake ports are pretty rusted. I'd do a compression test, but I almost know what it's gonna show...
The lube is a great idea... and lots of it. Compression readings must be taken with a starter driven spin.
Try to rotate the engine by hand first from the main pulley bolt.

Reman engine is likely in your future.

What did you pay for it? Is the floor solid? Transom? What about the vinyl?
All these factor in to a repower vs value.

But of course, if you just really like the boat and plan to keep it, roll up your sleeves and have fun.

 

[Mbrgr1]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

Well, that motor was built my Merc specifically for boats, powerful and torquey for a 4 cyl, but very odd, aluminum block, cast iron head from a Ford 460 truck engine, an alternator like an outboard with a very expensive water cooled regulator etc.

Big question is "why was it taken apart in the first place????"

It might be worth fixing, and a standard alternator conversion can be done, it all comes down to cost and determining what is wrong with that one.

Repower options are limited, you would have to redo stringers etc to accept a different motor, it can be done, but to get the same power and torque, you'd have to go to a small V8.

 

[Blueghost924]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

Thanks for the inputs. I initially bought the boat with the idea of replacing the motor...so basically I bought the boat. But on further examination when I got it home....well...

I'm not sure why it was taken apart - the previous owner only owned it for a year, and he has 2 other boats and really didn't have time to mess with this boat. Hull wise, the boat is solid with no sags or soft spots and solid exterior.

 

[achris]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

Hi Blueghost and :welcome: to iBoats....

If you have 770mm (30in) on the inside of your engine cover, and the (current) engine is later than 1982 (serial number for the first 470 of that series is 6218037) then a 'simple' option is a 4.3l V6. You'll just need a 'pulley to coupler' 4.3, the exhaust Y-pipe and to fabricate up a couple of engine mounts, and you're good to go.....

Chris.........

 

[Blueghost924]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

Thanks Chris....and thanks for the heads up about dropping in a 4.3 L Mercruiser.

I have to buy a marine battery anyway, so I may go ahead and try to turn over the old engine (just for kicks).

 

[Blueghost924]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

I looked at the serial number on the valve cover, and it's listing " 0C477522". Not sure if that would make sense...

 

[achris]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

I looked at the serial number on the valve cover, and it's listing " 0C477522". Not sure if that would make sense...

That's the serial number for the drive. Useful, when you have drive problems, but not the engine number. That's a 1988 drive with a 1.84:1 ratio....

The engine serial number will have the same format, and you might find it on a metal tag, starboard side... Just look at this picture.... (yeah, I folded :facepalm

 

[littlebookworm]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

Keep in mind that a remanufactured motor usually does not come with the accessories: carb, alternator, distributor, manifolds, or power steering pump. You'll need to buy those separately. Make sure ignition and fuel parts are marine-specific. Get shop manuals for whatever engine you decide to use and for your outdrive. You'll have to pull the drive to pull the engine; no big deal. You'll also need an engine alignment tool before you re-install the outdrive. If you decide to buy used parts, make sure they come with at least a 30-day warranty. Good luck. Hy

 

[Blueghost924]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

I have the serial number from the block...looks like it 0884795. Or it could be 0834795. The last 4 numbers I'm positive of...and I'm sure the first number is a 0.

 

[achris]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

I have the serial number from the block...looks like it 0884795. Or it could be 0834795. The last 4 numbers I'm positive of...and I'm sure the first number is a 0.

Hmmm.... Needs to be in this format...

0, then a letter (probably a 'B' or a 'C'), then 6 numbers....

Try getting a small digital camera down there and take a photo, then read that...

Chris.......

 

[Blueghost924]

Re: Bought 1987 Renken with 3.7L Mercruiser - worth keeping?

Thanks Chris. I took a picture with my mobile camera phone...in going with the info you gave me, the second digit has to be a "B" then, not an 8. Overall, I'm wondering if I could put a Mercruiser 4.3L in the boat...