OMC Hose routing

"Hi

Bought boat with OMC ou

"Hi

Bought boat with OMC outdrive w/350 chevy. Whole boat worked on by previous owner named Micky Mouse. The cooling system has four hoses that go to thermostat housing - none connected. Manual I purchased does not show the exact routing of all the cooling and exhaust hoses. Can someone send me a good clear diagram or at least a good description. My Email is [email protected] any help would be great."

"Paul you don't say what y

"Paul you don't say what year so this link will show you a 1989 5.7 but they all should be similar, look at item #53 which is the T-stat housing. Of the 4 hoses the big hose to the water pump should be obvious. The 2 hoses in the diagram # 43 are pretty straight forward the one on the right(looking at the engine from the front) goes to the port side manifold and the left side goes to the starboard manifold. The last hose #34 which I think is a actually a little larger in size comes from the transom (or oil cooler, power steering cooler if you have them) this is the raw water feed to the t-stat.

http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=comp&grou p=684&GroupList=678,679,680,681,682,683,684,685,686,688,687,689,690,691,692,693, 694,695,696,697"

"I should have put this in bef

"I should have put this in before - sorry.

The boat is an early seventies Aztec Imp. The present configuration has the two large jackets for the exhaust and each of these a large hose (rubber) going out the rear for exhaust. A smaller rubber hose at the rear - I think one is the intake from the impeller the other side may be the hot water outlet to the outdrive. These two little and two big hoses are at the rear.

On the front end of each jacket is two smaller hoses that go to the top of the thermostat housing - a total of four that come straight off the front of the jackets. There is a large radiator hose from the engine water pump but it goes to the base of the thermostat area where as these four rubber hoses from the front of the large exhaust jackets mount above the thermostat on a four eared fixture. ( there is also an electronic box sitting there which does not seem to have anything to do with the cooling but the book says nothing so I dont know )

I think each jacket has water flowing in a upper and lower chamber and looking at the holes it is supposed to allow flow over the exhaust even when thermostat is closed. But if they are connected wrong you get no flow to anyting. The OMC manual shows nothing like it.
I tried to include pic - Motor pic

Wow....sorry Paul I've nev

Wow....sorry Paul I've never seen one like that before hopefully someone with more experience with the older models like Morten will be along to have a look and help you out.

"First time I have seen this c

"First time I have seen this configuration. Looks like the thermostat housing is a 'double' version of the 2,5/3.0L. The manifolds must have twin chambers with water passing in at the back, out in front, through the thermostat housing/engine and out through the outer part of the manifold to the exhaust. The water in to the engine should be to the upper part of the thermostat housing and return from the lower to the outer of the manifold. However to be quite sure I would have to have a look at the thermostat housing top. Where the water comes in, there should be a bigger hole going down to the lower part of the housing next to the thermostat and a small channel to the 'exit' part. The water coming out from the engine/thermostat goes to exit and the outer part of the manifold.
Hope this was not too confusing."

"Thanks for getting back to me

"Thanks for getting back to me. I heard these were called log style exhaust manifolds and all four of the hoses go into a housing that is ABOVE the thermostat. I will remove it and get picture of inside to show but what worries me is the holes inside the four chambered piece are different sizes and shapes. I hoped someone out there may have an old manual etc ( last used in 1973) that showed a picture of the hoses. It may simply be top right of gooseneck to top right on exhaust jacket, etc. for all four. But with the different hole sizes I want to make sure for correct water flow. Also have no idea what the little electronic box is that is bolted to front of the gooseneck.Motor pic

"The box in front is the regul

"The box in front is the regulator for the generator. As for the hoose routing, a pick of the inside would help, but the system is the same as was used on the 2,5L OMC120. Even that had the water goming in at the riser at the back, went through the manifold, into the thermostat housing , through the engine or bypassed to the manifold and out again. If You may se that routing, Yoy have an answer to Your question. No rocket sience! I think You may se how it works when You lift off the thermostat cover, and I would not be surprised if the gasket used is the same as for the 2.5/3.0 L (120/140 OMC)"

"Managed to dig up this old pi

"Managed to dig up this old pic, not sure it it might help??OMC Cooling Layout

"A bit confusing as the stb an

"A bit confusing as the stb and port does not quite seem to pair up, but using the 2.5 ilustartion the 'inn' hose goes to 'upper' and out comes from the 'lower' niple of the thermostat housing top. 2.5 routing

Thanks for getting back to me.

Thanks for getting back to me. It looks like we would have had it wrong. The water flows in from the impeller on both lower sections of each jacket then the bottom hose on the jacket goes to the top port on the gooseneck. Water flows thru engine then back to gooseneck to upper part of jacket and mixes with exhaust in jacket. It is a strange setup and if it leaks we will have a real mess. If any one has first hand experience with one of these I would love to hear your thoughts and tips.

I dont see it much looking through a lot of this website so I want to take the time to say thanks to all the good people out there that reach out to hurting fools like me that get into these messes. I love restoring old vehicles and this is my first boat that is not an outboard. Spending your time helping others is most appreciated.

Paul D

"The set up is not that 's

"The set up is not that 'strange' just a bit 'old'. The main problems that was/is with the similar setup on the 2,5L was gasket leakage between the two channels and exhaust in the manifold: If exhaust leaks into the 'water in' channel there is a severe cooling problem. Further more there should be a very small 'leak' hole from the 'in' channel and down to exhaust in the exhaust bend. If that gets too big, exhaust may backflow, if blocked, the system does not drain out when You stop the engine. The next is the passage in the thermostat housing cove from 'in' to 'out'. If that gets 'blocked' and thermostat is closed, the water in the manifold starts 'boiling' and may create problem. If the hole gets too big, the water is bypassed out to the manifolds and not going through the engine!
I think Your biggest problem might be to get spareparts, but there should be no problem 'rebuilding' to normal manifolds where water only goes out."

"Hey Paul I believe u have the

"Hey Paul I believe u have the wrong fuel filter on your engine. By looking at the pic it looks like u are running a plastic filter and it might break open, then u will have a fire on ur hands or be stuck out on the lake. If it was me I would change it to a marine metal fuel filter."

"Good call Doug, didn't ev

"Good call Doug, didn't even notice as I was too busy looking at the T-stat housing. Definitely should be changed if not for the regs then at least for safety like you said."

"Yeah I have seen alot of boat

"Yeah I have seen alot of boat owners using this type of filter, dont they know is against the reg to have it and if they get caught with it they can have a big fine for it. Why would people put a plastic filter on? When I bought my boat it had the same filter on it and I threw it out. I bought the type that goes inside the carb. Cant wait to get mine on the water soon."

"In comparing the pic you post

"In comparing the pic you posted to the diagram in the '64-'86 Seloc maual, page 9-3, the hose routing was correct in the picture. On each side, the water from the intermiediate hsng. enters at the rear of the ex. manifold, comes out the lower front nipple, amd is routed to the upper nipple on the t'stat hsng. In a cold engine the water will flow through a metered orifice back out the lower hoses to the manifolds. In a warm engine it flows through the large hose down to the circulation pump, through the engine, up through the thermostat, and out the lower hoses."

"i have an omc sterndrive ele

"i have an omc sterndrive electramatic lower gearcase unit (76-77) judging by clymers repair manual.the motor (chevy 4 cy) has been rebuilt and a new makeup pump installed. as long as we keep tje rpm to less than 2000, it runs fine,but anything over 2200 runs hot . we have checked eveything possible, and have run out opitions ahy help?"