1988 Mercury 350 overhaul questions

[J. Mark]

I am in the process of stripping down and refitting a 1988 Marlin Ski Magnum. The Engine is a 350 Ski Competition. When I bought the boat I knew everything needed to be rebuilt, but I have run into some issues that are new to me as my previous engine work has been on Fords and automobiles.

The Velvet Drive transmission has fluid that looks milky-the hose to the cooler are cracked and I will replace them. Do coolers often fail and is there a procedure to test them before reinstallation?

The carb on the boat was an automotive Rochester Quadrajet. I would like to run the Edelbrock 1409 Square bore Carter/Weber style Carb, but know I need an adapter plate to make sure things seal properly. (Now you know I am an old ford guy) The boat did not have a wedge shaped spacer to keep the carb level. Is this something that is typically on these engines or is it an aftermarket add on. If so is it worth using?

I am also considering changing the manifold to a Edelbrock Performer 2104 (I think that is it) Will aluminum in a boat suffer from galvanic action if only used in fresh water? If so is an anode attached to the manifold sufficient or should I just make do with my cast iron manifold?

Currently the engine if a hydraulic flat tappet cam engine. Can a roller cam and lifters be used in a 1987-1995 Chevy 350 block without modification? I know on the Fold engines the blocks were different-what about these Chevys-someone educate me please.

Finally, the boat uses a hose off the standard water pump (where a heater hose would go on a car, runs to a box in the front of the boat and then a hose returns to the top of the thermostat housing. Looks much like a heater core set up, but I am assuming it is for some other purpose such as engine cooling. It has ducts up though the top of the bow. Is this what i believe it to be? Is it something that is beneficial, or is it just one more thing to leak?

Sorry to be so long winded and asking so many questions, but I have read and searched the forum and am still unable to find these answers.

Thanks in advance

 

[Big Boat Bay Buster]

Re: 1988 Mercury 350 overhaul questions

Here is a pic of my 1987, 260HP Mercruiser, 350CI. If you look down the center of the engine by the lifters, you will see 3 bumps(nipples). The machinist explained he could drill and tap the holes for a roller cam. Some minor machining by the timming chain area was needed also. I decided to go stock for a few reasons. 260 HP was plenty for a 21 foot bowrider, it was cheaper and it employed the KISS method (Keep It Simple Stupid). I was driving myself crazy trying to decide if I should go with GM Vortex heads, or aftermarket heads, what Camshaft?? Then what manifold would go with what head. Square bore or spread bore carb. What about the choke?? Cast or forged pistons??
If you are thinking of going with an edlebrock manifold, get the marine version, I believe it has a different metal coating inside the water jacket.
Sorry if I have not answered your questions directly, atleast I have givin you food for thought!!
Chris

 

[wca_tim]

Re: 1988 Mercury 350 overhaul questions

answers in text of your post...

The Velvet Drive transmission has fluid that looks milky-the hose to the cooler are cracked and I will replace them. Do coolers often fail and is there a procedure to test them before reinstallation?

Can't help with this one, but I bet someone will chime in that can pretty soon

The carb on the boat was an automotive Rochester Quadrajet. I would like to run the Edelbrock 1409 Square bore Carter/Weber style Carb, but know I need an adapter plate to make sure things seal properly. (Now you know I am an old ford guy) The boat did not have a wedge shaped spacer to keep the carb level. Is this something that is typically on these engines or is it an aftermarket add on. If so is it worth using?

not sure, but presumably if you change the manifold the carb will be level when you're done, no?

I am also considering changing the manifold to a Edelbrock Performer 2104 (I think that is it) Will aluminum in a boat suffer from galvanic action if only used in fresh water? If so is an anode attached to the manifold sufficient or should I just make do with my cast iron manifold?

look at it this way, even if it does corode, how much does a manifold cost? note in the worst case, we're talking years, not weeks. I took the aluminum intake off an engine after a year of operation in brackish, some salt and some fresh as well. I flushed it well after every time in salt and brackish, but the inside of the water pasages in the intake were fine. I'm beggin no problem at all in fresh water.

Currently the engine if a hydraulic flat tappet cam engine. Can a roller cam and lifters be used in a 1987-1995 Chevy 350 block without modification? I know on the Fold engines the blocks were different-what about these Chevys-someone educate me please.

no, as mentioned above. I just had a 385 ci stroker built from a 1989 block. I elected to go with a flat tappet cam for the first iteration - as long as you run the right oils to keep them in good shape you can make a lot of power with a hydraulic cam. the deal was that to properly machine and install factory style roller cam parts it owuld cost as much as it would to go with the retro upfit sets that don't require machining. I chose to spend the extra dollars on heads instead - a better investment in terms of horsepower per dollar at that stage in the game.

Finally, the boat uses a hose off the standard water pump (where a heater hose would go on a car, runs to a box in the front of the boat and then a hose returns to the top of the thermostat housing. Looks much like a heater core set up, but I am assuming it is for some other purpose such as engine cooling. It has ducts up though the top of the bow. Is this what i believe it to be? Is it something that is beneficial, or is it just one more thing to leak?

I got no idea about this - your set up isn't like one I've had exsperience with, but again, I bet someone will chime in on it....

Sorry to be so long winded and asking so many questions, but I have read and searched the forum and am still unable to find these answers.

Thanks in advance

You're welcome, I just home its helpful...

 

[J. Mark]

Re: 1988 Mercury 350 overhaul questions

Thank you. The answers are indeed helpful. I have a line on an intake that has been ceramic coated (IIRC) for $75.00 but I believe the seller is probably the lying SOB that sold me the boat and I'd rather pay full retail than give him any more money.

As to a Roller cam-I agree that a hydraulic cam cam make plenty of power in the RPM range that these boats operate in. While a screaming 7000 RPM engine might be fun in a light car, I know it is not right for a boat. I will likely stick with a stock cam and mine may be fine. I'm pulling the engine tomorrow and will begin teardown to see just what kind of shape the guts are in.

As to the Carb sitting level on a new intake-nope, the engine sits at about a 12 degree angle in this boat, so unless the intake is angled (and I have yet to see one anywhere that is) the carb will not sit level. I've found plenty of tilt shims such as this one http://boatdesigns.com/prodinfo.asp?number=90-455 but I have no idea if these are commonly used or if this is just a gimmick. It makes sense to me that a carb needs to sit fairly level for the floats to work properly, but I don't know what degree of tilt they can stand before it becomes a problem.

The "radiator" up front is a minor issue and a curiosity for the most part. I'd like to eliminate it if possible, but it isn't a big deal either way.

As to the transmission oil cooler-if I can't find a way to test it, I guess I'll just pay the 65 bucks or so and replace it. In the grand scheme of things, I'd rather waste a little money than have to redo the work.

Thanks again and if anyone has any other opinions, I'd like to hear them still.

 

[Mkos1980]

Re: 1988 Mercury 350 overhaul questions

While it was apart I would have had it tapped and would have run Mercruisers lates roller cam and vortec heads. You can never have enough pulling power. But if its already all together its still a good package.

 

[dan t.]

Re: 1988 Mercury 350 overhaul questions

many of these blocks came already drilled and tapped for the factory roller cam setup. i have a 94 block in my pickup that came with a flat tappet cam but is drilled and tapped for roller, it is also equipped for a mechanical fuel pump.if you are rebuilding anyway ,check your local wrecker for a rebuildable core with a roller setup good luck

 

[Bondo]

Re: 1988 Mercury 350 overhaul questions

As to the transmission oil cooler-if I can't find a way to test it,

Ayuh,... That's pretty simple actually,...

Block off the ports,+ pressurize it with Air,.... If it leaks,... The pressure will drop,+ You'll hear it...

would have run Mercruisers lates roller cam and vortec heads. You can never have enough pulling power.

Ayuh,... Sage Advise right there,....

The Heads alone are about a 20/30hp increase....

 

[J. Mark]

Re: 1988 Mercury 350 overhaul questions

Well, a quick update.

Pulled the motor yesterday and started tearing down today.

Internally it is much claner than I would have expected. It failed a compression test miserably, but . . . head gaskets did not appear to be blown and cylined wals looked undamaged with no ring at the top or any significant carbon build up . Tops of the pistons are carbon coated, but not thick and flaking, just a nice even coating.

Block had water in the oil, but no apparent damage. Piston skirts are unmarked and I pulled the rear main bearing and though it had some minor wear, it wasn't bad at all and the crank journal looked fine.

Stopped the tear down there as I don't have a harmonic balancer puller, but everything looks rebuildable to the naked eye. I need to get it torn down the rest of the way to mic the cylinder walls and see if it needs to be bored, but I think this is going to be a simple job with rings, bearings, gasket and those other things like oil pump, timing chain and gears and seals and freeze plugs.

I am strongly considering getting the block vatted and magnafluxed before I go any farther.

On the downside the fluid in the velvet drive looked like pepto bismol. The hoses were very deteriorated and I will test the cooler, but I fear that the water contamination might require something more than a flush and refill.

Any velvet drive experts care to comment on how to proceed with it?

 

[wca_tim]

Re: 1988 Mercury 350 overhaul questions

A couple more thoughts, You can just about buy a reman short or long block for what it will cost to rebuild the old. I've done both and would do the reman again except in situations where I wanted something more.

I'm betting your lifter valley isn't machined or driled for the spider to hold the factory roller cam in. I think especially for 88 and 89, they didn't. The comp cams extreme marine cams are popular for marine builds as are some of the crane hydraulic cams. Just run high zinc oils, such as chell rotella and you'll be golden.

Sorry no help on the velvet drive, never had one.

Well, a quick update.

Pulled the motor yesterday and started tearing down today.

Internally it is much claner than I would have expected. It failed a compression test miserably, but . . . head gaskets did not appear to be blown and cylined wals looked undamaged with no ring at the top or any significant carbon build up . Tops of the pistons are carbon coated, but not thick and flaking, just a nice even coating.

Block had water in the oil, but no apparent damage. Piston skirts are unmarked and I pulled the rear main bearing and though it had some minor wear, it wasn't bad at all and the crank journal looked fine.

Stopped the tear down there as I don't have a harmonic balancer puller, but everything looks rebuildable to the naked eye. I need to get it torn down the rest of the way to mic the cylinder walls and see if it needs to be bored, but I think this is going to be a simple job with rings, bearings, gasket and those other things like oil pump, timing chain and gears and seals and freeze plugs.

I am strongly considering getting the block vatted and magnafluxed before I go any farther.

On the downside the fluid in the velvet drive looked like pepto bismol. The hoses were very deteriorated and I will test the cooler, but I fear that the water contamination might require something more than a flush and refill.

Any velvet drive experts care to comment on how to proceed with it?

 

[J. Mark]

Re: 1988 Mercury 350 overhaul questions

Nope, the valley isn't drilled for a roller cam.

No biggie, the heads are the pressed in studs without pushrod guides and would also have to be replaced to convert.

I'm going to probably just do a very basic overhaul on it and call it a day. I want the boat to run well and be reliable. If I find that the boat after completion is something I am satisfied with and just want more power, I can drop another engine in it down the road. Thanks again

 

[Mkos1980]

Re: 1988 Mercury 350 overhaul questions

No biggie, the heads are the pressed in studs without pushrod guides and would also have to be replaced to convert.

You dont have to change any of that. Roller cam, GM Timing set with thrust plate, lifters, dogbones, hold down and 7.200 Pushrods. You prob have self aligning rockers. I converted my vortec heads to screw in studs for a total of 40 bucks. Pics available for anybody wondering.

I paid 40 bucks for my Lifters, hold down retainer, dog bones and pushrods. (All items came off a 93 LT1) and the timing set from GM with plate was 53 bucks. They sell Mercruisers RamJet cam on ebay for about 130 bucks from overstock suppliers and people removing them to add something more aggressive..