2.5 OMC not running correctly.

[Shadow91]

Okay, so finally got my boat to start after replacing the plugs, cap, rotor, coil, points, condenser and slave solenoid. only ran it long enough to know that it would start..

So today i finally took her out on the maiden voyage and after letting it warm up for a little while it ran fantastic. Had lots of power and had no issue getting up to speed. Well after about 5 minutes of running the exhaust coupler completely just blew out filling the boat with exhaust fumes and being louder then ever (running basically open headers at that point)

ran to autozone and grabbed an exhaust repair kit and then back to the water. After getting back on water went to start it and it just would not idle to save my life. i could start it at about 1500 rpms and it would bog hard or die if i tried any more throttle. and again just would not idle. Very hard start and just no power what so ever. finally removed the spark arrestor filter thing and it ran slightly better. still couldnt get it to idle long enough to put it in gear. Well finally after removing the dog house it ran a lot better but still had very sluggish power.. then the exhaust blew out again and the serp belt snapped - so that ended my day.

Now then, i have very LITTLE experience with carb'd engines. Would the exhaust not being properly sealed cause runabailty issues? And is there suppose to be some sort of fresh air intake system for the carb? Also, where is the best places to find parts for this damn engine?

So far i know i need
serp belt
4 inch exhaust coupler
water hose (from head to intake)
fuel filter


Anything else i should get that any of you would suggest? trying to get this running the best way possible. Also gonna get those ear muff looking things to try and tune this bad boy before heading back to the water.

engine model #252FTHROTR Serial # J 761532
Outdrive # 982740 (serial number is unreadable)

 

[Scott Danforth]

if the rubber exhaust hose blew, there was no cooling water and the rubber got hot enough to come apart. did the bilge fill up with water when the hose blew? if not, you have no cooling water.

I bet the motor temp was high enough to score the pistons which is why it would not run higher than 1500.

you have some serious issues with the motor and drive. stop using the boat until you get them fixed

first, do a compression test. if you are less than 130 psi in any of the cylinders, you may want to not go any further while you evaluate if the boat is worth a replacement motor

you have a stringer drive

when was the raw water impeller replaced? if you dont know. replace the whole raw water pump assembly after you confirm your motor is healthy

 

[Shadow91]

Okay, so just went and did a dry compression test on the engine..

Reading from the crank pulley back (bow to stern)
1 - 150 psi
2 - 130 psi
3 - 130 psi
4 - 145 psi

At this point, would that be enough to drive the boat? Or am i looking at complete overhaul/ replacement engine?

And absolutely no idea on the raw water pump. From my understanding the boat sat for roughly 3-4 years before i got it due do a snapped axle on the trailer.

 

[Scott Danforth]

your lucky, your motor may not be toast.

I suggest you find out quickly about the raw water pump and all other maintenance needed on boats. yours is shot and you are not pumping water or you would have filled your bilge with water when the exhaust blew.

 

[Shadow91]

The boat was flooded up to the carpet before I got her back on the trailer. I just assumed it was the two small holes someone had drilled on the bottom of the hull not correctly patched!

Honestly it makes me feel better knowing that that's where the water leak was from..

Just talked to the local boat service center and it's about $115 for the raw water pump, and $45 for the coupler. Gonna order those up along with a new belt and then take it to them to asses the rest of the engine. Figure a few hundred dollars in repair to someone that knows that they are doing is better then ruining a ~$2-3000 engine.

 

[Scott Danforth]

You shouldnt need a coupler. You will need a new exhaust hose. You will need a new raw water pump (get complete pump).
If your water was high enough to get on the carpet, your starter and possibly the alternator were under water. You may be replacing them soon as well. Your trim motor was under water. That may soon fail

 

[Shadow91]

Not sure if you understand what exactly broke, so i snapped a few pictures.

This is the couplet that blew out from dry rot/age

and the hose that separated on me

 

[Shadow91]

I believe this is all i need for the exhaust?
Sierra exhaust hose 18-2779

https://www.amazon.com/Sierra-International-18-2779-Exhaust-Hose/dp/B001RIPNO2

 

[Scott Danforth]

I know what you are talking about. you have the terminology wrong

you are missing the exhaust hose because it blew out from lack of water. the flaking and burned paint on the riser casting says that that part alone got over 400 degrees. you have no water flow. zero, nada, not a drop coming from your raw water pump. as in you need to fix that before you worry about the dang exhaust hose

your water supply hose to the manifold separated on you because you were running steam in your motor vs water. you have steam in your motor because you most likely dont have a drop of water coming from your raw water pump to keep your motor cool and the hose has never been changed

your exhaust hose is the least of your problems. the exhaust hose failure is a result of your other issues

just so you are clear

this is a coupler, specifically an omc coupler for a stringer. you do not need a coupler

this is an exhaust hose (found on iboats.com for $28) http://www.iboats.com/OMC-Sterndrive...view_id.269606 you need an exhaust hose

this is the raw water pump that you need found on iboats for $67 http://www.iboats.com/OMC-Sterndrive...view_id.270185

you need a raw water pump

and you need to pull the drive apart to repair it.

and when you order your parts from iboats, make sure you get the discount

this is the banner above the current iboats forum member discsount

 

[Shadow91]

My apologies. That is why i took the pictures to clarify any misunderstandings.

So is there more then one pump flowing water? The one on the engine, what is its purpose vs the raw water pump? Sorry for the uneducated questions, just trying to fully understand the cooling system in a boat.

Also, what is the best way to test to make sure the system is functioning correctly after replacing the raw water pump? Should i use one of those ear muff looking 'flush' things or try sticking the drive in a storage bucket full of water?

And it seemed that when the engine was running, i was getting some sort of water circulation out the back side of boat. Im probably wrong, Just what i observed while running it. Is that another system all together? (not the bilge pump)

Again, sorry for the lack of understanding. Im very quickly understanding there is some major differences between marine engines and automotive.

And will be ordering the Sierra Part #'s 18-3386 and 18-2779

 

[Shadow91]

And just so I am clear, im looking at replacing 18, 19, 20, 21, 35, 46, 22, 23, 24, 25, 26, 30, 47 and 48 (not necessarily all those, just that general area) for the raw water pump? Your image didnt appear with what you had posted.

 

[Shadow91]

Well after a bunch of searching i realized i was looking at the wrong water pump.. But should i be concerned about that one as well?

It seems i need to replace this one

Does anyone have a write up or good link to access this one? Looks fairly involved. Also, as far as service manual goes, any recommendations?

 

[Scott Danforth]

the pump I linked above is the correct pump for your stringer

get the factory manual not a clymer or haynes or chilton or seloc.

or this site has videos and writeups http://www.sterndrive.info/id327.html

basically pull the drive, split the drive, unbolt old water pump and throw away, install new water pump housing, bolt in place, then install impeller, cover, etc. re-seal, then mate the lower to the upper, pressure test, refill with gear oil, then reinstall the drive.

the raw water pump pumps water from outside the boat, thru the drive, into the boat via the intermediate housing and fills your motor with water thru the thermostat housing. any additional water flow is pushed into the exhaust manifolds out your hose that blew up. the water cools the manifold and the riser, and is expelled with exhaust thru the outdrive and out the prop

the circulating pump on the front of the motor simply circulates water within the block and heads until the thermostat opens and it discharges some hot water allowing some cooler water to come into the block. the thermostat maintains block temperature.

also note that the external splines on shaft #28 and the internal splines on shaft 21 are prone to failure. while you have it apart, inspect the splines. if they are still trapezoidal in shape, you should be fine. if the splines are worn looking more like thin triangles, replace the two shafts.

 

[Shadow91]

Okay, so trying to put a parts list together to order before i start ripping this thing apart. Have a few questions as far as which parts i do need.

I assume while im already pulling the drive apart to replace the water pump i should order a upper gear case seal kit (maybe a lower as well???)
Im not certain between two different part #'s.. I have both 87650 or 87651 as options. No idea what is different.

Then how do i know if i have a low profile or high profile shafts? Trying to make sure i know price and availability if i get in there and they need to be replaced.
So either (picture #s 21 and 28)
22412 low profile upper shaft
22410 low profile lower shaft

and

22423 high profile upper shaft
22411 high profile lower shaft

I would then just need the water pump kit (12190) and replace the woodruff key, part # 89595

Then I should just need gear oil I would assume? Anything else I should order before i rip into this? I want to be as prepared as possible.

All part numbers are GLM numbers taken from http://www.boatparts.ca/omc-parts/upper_gearcase_stringer_drawing.html

 

[Shadow91]

And also, I understand needing the raw water pump replaced, however, i still need to get the engine running halfway decent? The raw water pump wouldnt effect the runability of the engine I would assume? Unless just overheating and causing issues there. Is there any way to check the engine any more before I drop some cash and time on the water pump on the drive?


You also mentioned pressure checking the system in your above post. How exactly do you do that?

 

[Shadow91]

Well finally got around to replacing the pump assembly. So far everything looks good with very minimal signs of wear from the impeller. Only thing i noticed with it all was that the retaining ring (between #22 and #23 in post 12) is completely missing. Not sure how important it is but I know i need a new one. However, i can not find the ring on any online sources and even the exploded veiws show it, but there is no number or link attached to the ring.

So can just use any retaining ring? Like a snap ring from my local hardware store or is it pretty important to be the exact one? And if so, any info on where to get it?

Also, as far as the sealer that they use in the videos you linked, can i use just any RTV based gasket maker or do i need that specific stuff they use in the video? (they use Evinrude/Johnson gasket sealing compound)

Thanks again for all the help