'87 OMC 4.3 V6-Water Flow Question

[littletoes]

Guys, can somebody answer this for me;

When you hook a water hose to the lower intake holes, is water supposed to circulate through the entire block?

And if it isn't, what the heck could be stopping it??? I've ran the hose, and pulled the hoses on top of the engine, where I would guess the thermostat is located, and I have nothing.
Now, if this as simple as just a "stuck" thermostat, I can change that....but I don't "know" about boats....worked on quite a few trucks and cars, even tractors and big rigs, but boats? Well, thats another story!

Thanks Guys!

 

[HT32BSX115]

Re: '87 OMC 4.3 V6-Water Flow Question

Guys, can somebody answer this for me;

When you hook a water hose to the lower intake holes, is water supposed to circulate through the entire block?

And if it isn't, what the heck could be stopping it???

Howdy,

No. The water will not probably flow at all.

You have a raw water pump (rubber vane-type impeller) on the back of the drive that pumps water from the lake to the t-stat housing!

The circulating pump (a "regular" automotive type {marine} belt driven water pump) circulates water through the block and heads mixing *some* of the colder water from the raw water pump in whatever amount that the t-stat lets in to maintain temp.......

ALL the total from the raw water pump will go to the engine....BUT most will bypass to the ex-manifolds and be pushed out thru either the top of the riser elbows (or the top of the bat-wings if your still unfortunate enough to have them.......get rid of them btw!)

If NO water is coming out of the relief ports at the transom or exhaust in the center of the prop (or the ex bellows), you may need to replace your raw water pump and/or find the obstruction(s) between the impeller and the t-stat connection or obstructions to the water exiting the manifolds(clogged with corrosion).

Unless you have severely rusted manifolds/risers when the pump is working it will pump water but it will not usually prime all by itself. You must provide positive pressure water to it (using "muffs") or be in the lake!



Regards,


Rick

 

[littletoes]

Re: '87 OMC 4.3 V6-Water Flow Question

Rick-Thank You VERY much!

I was worried no water would burn up a water pump or something....amazing what I can't remember from last year (when I purchased this boat).

If you don't mind me asking another question, what are the "Batwings"?

 

[Lou C]

Re: '87 OMC 4.3 V6-Water Flow Question

The Batwings were the one piece manifolds that OMC used from about 85-90 or so, they were used only on the V-6 engines, and eliminated the joint between the riser and manifold. Some don't like them, I happen to like them, no joint there to leak and that joint is the Achilles heel of I/O exhausts, that's why Mercruiser went to the dry joint exhaust....

The pic of the outlets shows what they looked like compared to the new ones I put on, after 5.5 years of use in salt water. I cleaned out the clog in one port and they are still usable. Put the new ones on to be on the safe side. The engine pic shows that there was no corrosion, no leaks and no rusty exhaust valves. So you see the bat wings were not at all a bad idea, just expensive to cast. In fact, Hi Tech marine in Australia makes some very high priced one piece manifolds out of stainless, and the advantage of them besides being stainless, is exactly what I said, no joint to leak. In fact they make a point of this on their website....

They are no longer made, so it's a moot point, and there is a 2 piece conversion for these engines now, but I am glad I got an extra pair when I could (and BTW, the price then was 400 bucks cheaper than that 2 piece conversion is now).....

 

[raybeau]

Re: '87 OMC 4.3 V6-Water Flow Question

I had my impeller replaced and they never did remove the old impeller pieces which caused a major block of water passing into my motor. Check outside screens on bottom intake sides of outdrive. Make certain water hose line that feeds thru the transom is clear and connected. (it's a tough connection to make).

Here is where we found the problem on our 86 SeaSwirl 4.3 Cobra.....
Remove the top hose from the power steering coolant canister at the rear of the engine at the transom wall. Check to see if there are any impeller pieces sitting inside of it. Use a small hook or needlenose to clean large pieces. If there are even small pieces then do the following: remove the water feed line from the thermostat housing. Flush water using a hose thru thermostat feed line backwards to flush out the power steering fluid coolant canister. I used a hose I connected directly to the power steering canister bib to flush and remove pieces of the old impeller. I was amazed what was left in there. It is the one place you have to totally trace out to learn that it is the major water obstruction path besides the impeller for blocking water getting into these engines.

Howdy,

No. The water will not probably flow at all.

You have a raw water pump (rubber vane-type impeller) on the back of the drive that pumps water from the lake to the t-stat housing!

The circulating pump (a "regular" automotive type {marine} belt driven water pump) circulates water through the block and heads mixing *some* of the colder water from the raw water pump in whatever amount that the t-stat lets in to maintain temp.......

ALL the total from the raw water pump will go to the engine....BUT most will bypass to the ex-manifolds and be pushed out thru either the top of the riser elbows (or the top of the bat-wings if your still unfortunate enough to have them.......get rid of them btw!)

If NO water is coming out of the relief ports at the transom or exhaust in the center of the prop (or the ex bellows), you may need to replace your raw water pump and/or find the obstruction(s) between the impeller and the t-stat connection or obstructions to the water exiting the manifolds(clogged with corrosion).

Unless you have severely rusted manifolds/risers when the pump is working it will pump water but it will not usually prime all by itself. You must provide positive pressure water to it (using "muffs") or be in the lake!



Regards,


Rick

 

[HT32BSX115]

Re: '87 OMC 4.3 V6-Water Flow Question

Flush water using a hose thru thermostat feed line backwards to flush out the power steering fluid coolant canister. I used a hose I connected directly to the power steering canister bib to flush and remove pieces of the old impeller. I was amazed what was left in there.

Hey! Welcome aboard!


Yes. Most people forget that there's a place for all the pieces to collect.

The oil cooler in my 454 Bravo was so COMPLETELY clogged with impeller fragments I wondered how ANY water got through....The previous owner told me "Oh yeah! I replaced the impeller last year!!" :facepalm:. ........

This is also partially why a LOT of bigger boats intended for salt water have "sea-strainers"(raw water filters), to pick up the debris before it goes someplace hard to find!

The Batwings were the one piece manifolds that OMC used from about 85-90 or so, they were used only on the V-6 engines, and eliminated the joint between the riser and manifold. Some don't like them, I happen to like them, no joint there to leak and that joint is the Achilles heel of I/O exhausts, that's why Mercruiser went to the dry joint exhaust....

Yeah. I know I don't like them. For an older boat that someone else maintains they're a sort of a "ticking time bomb"........ This is because while, yes, you do not have a joint to leak, if someone tries to get "max" time out of them, having NO way to inspect inside (breaking the joint and looking) You just have to be REALLY lucky picking the time to replace them.

If you let them go a leetle bit too long (long enough to start leaking)....... "Murphy" will have them leaking right about the time you winterize.
THEN, they sit all winter with that water that ran into the exhaust valve that opened when you shut it down for the last time of the season!!

Although I suppose the same could happen if you let "Dryjoints" go too long........... and you cannot see inside them either!!!

The biggest problem with the Batwings now are that you cannot buy them. And people are absolutely trying to get the MOST time out of them as they can. I get that. But now they are at the greatest risk because a lot of people are trying to get them to go "One more Summer"

Cheers,


Rick