TOPIC: 165 HP Mercruiser options

Alrighty...

i have a 1974 Arrow Glass Cheetah. It currently has a 165 HP Mercruiser, in-line six cylinder. I have been told the engine block is cracked. I several question about this situation.

First, if I fire it up and discover that just the outer block is cracked, can this be repaired?

Second, what are the odds that anyone here in these forums happens to have a spare one sitting around that they want to get rid of cheap? This is a budget project and the wife will NEVER approve a major expenditure.

Third, what other engines do I have to choose from that will make for an easy swap? Or am I going to be forced into replacing everything if I don't find an exact replacement?

Let's here from you experts,
Richard

If I recall correctly, that is a Chevy inline six. But, marine engines are cammed differently. They have a totaly different powerband than an engine used in an automobile application.

Is there water in the oil? Milky engine oil contains water - clean oil does not - unless it's just been changed and hasn't been run...as in changed to make it look better when selling it.

People say JB Weld will repair a crack..I've never tried it. These open systems don't run under the same high pressure as closed system in a car..I'd say it's worth a try. You'd have to clean the crack area - possibly drill small holes at either end of the crack to stop it spreading before patching with JB.

Peter_Crowl wrote:

People say JB Weld will repair a crack..I've never tried it. These open systems don't run under the same high pressure as closed system in a car..I'd say it's worth a try. You'd have to clean the crack area - possibly drill small holes at either end of the crack to stop it spreading before patching with JB.

This may be a viable option. It's been a while, but I think Peter is correct, that this is a raw water colling system ( no heat exchanger ). So, that means no cooling sytem pressure. Run it and do as Peter has suggested, check the oil to see if it looks like a "milkshake".

Marathon6: As I understand it you are correct. A 250ci Chevy, but cammed way differently. Automotive engines are built with flexible rpm ranges in mind to accomodate consistantly fluctuating acceleration patterns. Boat (and airplane) engines are designed more for even, steady rpm speeds. Boat engines are also cammed with a fierce low end in mind. Mad torque in the bottom rpm range to break the friction and surface tension of the water. Once the boat is moving it settles into a a more subtle torque curve to maintain speed evenly. That's just my take on it, correct me if I am worng. :-P

Peter_Crowl: I was wondering if that would be the case. It seems with the lake pumping unlimited amounts of water through it, never recycling heated water, the temps would not be anywhere near as extreme as an automotive engine. But me being a novice I was waiting for independant confirmation on that.

Now, the boat has been sitting uncovered in a field for at least eight year. I will not take for granted that the oil is not contaminated from that alone. My thought was this: I will change the oil to make sure it is good, throw a clean can of fuel temporarily into place, hook it up to a battery and fire it up. After a few minutes I will shut it down. If the crack is on the outer block I should have seen water spewing out, or leaking out. If it is on the inside of the block I will find my fresh oil change milky and contaminated. If the leak is on both, I will see both of course. I can make a decision from there I guess.

Does this sound logical?

rsparksjr wrote:

Marathon6: As I understand it you are correct. A 250ci Chevy, but cammed way differently. Automotive engines are built with flexible rpm ranges in mind to accomodate consistantly fluctuating acceleration patterns. Boat (and airplane) engines are designed more for even, steady rpm speeds. Boat engines are also cammed with a fierce low end in mind. Mad torque in the bottom rpm range to break the friction and surface tension of the water. Once the boat is moving it settles into a a more subtle torque curve to maintain speed evenly. That's just my take on it, correct me if I am worng. :-P

Peter_Crowl: I was wondering if that would be the case. It seems with the lake pumping unlimited amounts of water through it, never recycling heated water, the temps would not be anywhere near as extreme as an automotive engine. But me being a novice I was waiting for independant confirmation on that.

Now, the boat has been sitting uncovered in a field for at least eight year. I will not take for granted that the oil is not contaminated from that alone. My thought was this: I will change the oil to make sure it is good, throw a clean can of fuel temporarily into place, hook it up to a battery and fire it up. After a few minutes I will shut it down. If the crack is on the outer block I should have seen water spewing out, or leaking out. If it is on the inside of the block I will find my fresh oil change milky and contaminated. If the leak is on both, I will see both of course. I can make a decision from there I guess.

Does this sound logical?

Yep!!

Also correct, you need the bottom end "grunt" to get up!

Whattaya got to loose :~)?
You'll need a large vessel to run the lower in - or a way to get water to it. I have OMC stern drives - I don't know if Mercs use muffs or need a tank.

" I don't know if Mercs use muffs or need a tank. "

Ok, i'll be honest. I didn't understand any of that one.

Well - it needs to either be run in a tank of water - like a horse trough - or it needs to be fed with a hose through the use of muffs - wait here for a minute while I run down the hall and check something out -

Ok - here you go - www.perfprotech.com/store/catalog/Motor-Flushers-muffs,2655.aspx

These or something like them.

Ok, I see now. I'll have to look into how the water gets itself into the motor then. Seems like it should be an easy discovery. I just wish it weren't storming right now, I am eager to get to work on it.

Typically, the inline 4 & 6 cylinders crack horizontaly and usually only externally. Look under the manifold for the crack in the block.

BUT, the manifold may also be cracked. Look along its lower section. If the manifold is cracked, then big $ for that part.

The engine block is a GM 250 CID. You could find a block & swap the camshaft, but then you may as well do a complete rebuild at that point.

As for running the engine, you can use flush muffs on a MerCruiser. Truthfully, I don't think you can get a true picture without driving the boat. High RPMs cause high vibrations and higher heat levels that may cause problems to show up that won't at idle.

If the boat has been sitting that long I would expect stuck rings and/or valves.

Jim

Jim, you make the situation sound pretty dire. Am I best off just planning on a rebuild?

rsparksjr
Being from Idaho, I run into alot of this. Folks not winterizing correctly.
I look at alot of boats, I currently own 5. All but one are stren drive Mercruisers.(I like the stern drives over the outboards. But that is just me.)
Generally the blocks do split horizontally and outward. But again generally. You can hook up muffs, we call them Fake a Lake.
They go over the water intakes on both sides of the lower gearbox and supply the water pump. I use this method alot for anything I have to do with the engine running. But I do not run the engine up over a high idle. All of the mechanicals are running "unloaded".
But you will be able to determine if the engine is cracked internally if you get the "milkshake" oil. Pull the plugs and look for any moisture there also. Check everything that is not supposed to have water in it. If you don't, you may be stranded on the water.
JB Weld will work, but it is a band-aid on a wound that will not heal itself. I do have friends that are running boats right now that are JB welded. If budget allows, do a rebuild on another block, or replace it with another running marine engine. Reliability, longevity and piece of mind all play parts in the equation.
I have a good friend that is running the GM 250 165hp Mercrusier in a 19 foot Reinell and the low end torque, fuel economy and the general easy servicabilty are great. The boat is a 1971 and it is the original engine and I don't think the thing will ever die. It has rescued me a time or two. Good engine.
You will not be displeased when you get yours sorted out.

K W block seal has yet to fail me from diesel engines to gas engines it can be purchased at Auto Zone, O Reileys etc...

I have welded a good bit of cast. Pefecting my work at work in the mill cause, any thing that break needs to run like it was yesterday. I have some advice that you must drill holes at the ends of the cracks or it will continue cracking. This is done because cast expands and shrinks alot with heat( like when welding). I use nickel rod 99x or soft weld. I mentioned thes because epoxies would fail the same way if the stress was not releived by the small hole at the end of the cracks. Hope this helps and good luck

DelRay wrote:

K W block seal has yet to fail me from diesel engins to gas engins it can be purchased at Auto Zone, O Reileys etc...

I was discussing the use of block seal with a friend as I have a cracked OMC V6 Buick. What I don't see is how you'd introduce the block seal to the engine and get it to function/seal.

These being open cooling systems - where do you put the sealer? If you could get it in isn't it meant to seal by being forced to the crack as part of the recirulation process of a closed - pressurized - system?

Good question! A phone call to KW might be helpfull. They have helped me in the past.

Dont play around with dump in crap invest in a short blockhave your cam micked to check wear if bad install a new one dont cut corners in you power plant nothing is worse than beeing stranded when you could have helped it.