Penta 270 Troubleshooting

[thumperfbc]

Hi All,

First post here, thank you for the opportunity to ask it.

This past weekend a buddy of mine borrowed my boat for a trip to the lake. Once they got it in the water they idled it for about 10min and then went on their way. After about 5 minutes of cruising he said they heard a dramatic change in the noise signature from the engine and then steam started to pour out of the engine cover. They shut it down right away and discovered that an exhaust hose blew a hole a few inches past the header.

In their course of troubleshooting the problem, they took the thermostat cover off and started up the engine. He reports NO WATER flowing through.

So, my question is this: Is the blown hose a symptom of a great problem? Bad water pump? Belt driven pump, by the way.

My mechanical knowledge isn't great when it comes to boats, so I apologize if this is a dumb question, but is there a separate impeller somewhere, or is the water pump solely responsible for sucking up the water from the lake and transporting it through the system? I just don't want to do the easy fix of replacing the hoses if there is a bigger issue to be found.

Any advice on this problem and how I can find the ultimate cause, if there is something more, would be great.

The boat is a mid 70's Enterprise tri-hull. Penta 270 outdrive and a 302 V8 engine.

Thanks!

 

[captmello]

Re: Penta 270 Troubleshooting

Go to this link, type in aq190 in the 'engine type' box. Download the owners manual. It has some good info including some description of the cooling system.

http://www.volvo.com/volvopenta/global/en-gb/marine_leisure_engines/parts_service/publication_search/publication_search.htm

I'm not sure why the hose burst. there is little to no pressure in the hose.

Are you referring to #16 on this parts breakdown?

http://www.volvopentastore.com/Exhaust_Manifold_And_Installation_Components_Aq190a_76/dm/*******.179986439--**********.488996764--store_id.366--view_id.316951

If there was water coming out the exhaust, than the raw water pump is pumping. Its on the lower, front, port side of the engine behind a pulley.
That impeller should be changed every 2 years. If this pump were to fail, it would probably not change the pitch of the motor.

The other water pump just circulates water in the block. These pumps last for a long time, but then again, you have an old boat. If that pump went out, the engine would overheat and could change the sound of the engine. However it would not cause the manifolds to overheat or have any effect on the riser hose.

Did the boat overheat? If so, that could cause further issues.


You'll have to pull the riser/elbow off to replace the hose. #5/#3 (port or starboard) in the link above. I would suppose that is that hose blew open, the motor could change in sound as well.



Very hard to say whether you have additional problems.

Let us know what happens.

BTW, welcome to the forum.

 

[thumperfbc]

Re: Penta 270 Troubleshooting

Thanks for the info. How can i test the cooling system? The hoses dont concern me. After the one blew i pulled them all and they are in awful shape. I just dont want to swap the hoses and take it to the lake if there is still a issue. Whats the best way to check the impeller and block pump? I can change the hoses and drop the boat in the river for troubleshooting purposes.

 

[Howard Sterndrive]

Re: Penta 270 Troubleshooting

The hose likely melted when cooling water flow ceased due to failed impeller.
I doubt it blew.
Change the impeller.

The exhaust got loud because the manifolds were dry.
Then the hose melted.
Then it got even louder.

 

[tbear1964]

Re: Penta 270 Troubleshooting

If it's not a thru hull exhaust, the exhaust bellows might have melted too. Don't ask me how I know......

I agree with Howard. Check the impeller first. Since it's not in the lower unit, it's easy to check/change.

 

[thumperfbc]

Re: Penta 270 Troubleshooting

So, you are recommending I change the impeller out...

The manual linked above (thanks for the link!) shows the process and it looks really easy... However, it doesn't list a part number for the impeller. Does anybody know the number so I can buy the impeller online (ebay or somewhere?)...

Thanks!

 

[thumperfbc]

Re: Penta 270 Troubleshooting

Also, the piping the comes out of the exhaust manifold looks different then the diagrams... It's very similar, but it is several pieces assmebled together, and not one long single bent pipe like the diagrams. I'll get some pictures here in a few...

 

[thumperfbc]

Re: Penta 270 Troubleshooting

Ok, here are some pics...

Overall side shot...

Closer shot of the exhaust piping (tubes removed...)

Here is the damaged piping... There are 2 pieces of rubber tubing per side, all 4 pieces are VERY corroded.

Does this picture show the raw water pump? Is there where the impeller is located? Looks easy enough to change...

And finally the water distro area... Is it normal to have NO thermostat??? I expected to find one when I opened it up, but there wasn't one! I assume I need one?

Thanks!

 

[Howard Sterndrive]

Re: Penta 270 Troubleshooting

Actually to me, that X pattern where the hose split says torsional failure- vibration, repeated twist of the engine - age

Change the impeller anyways

 

[thumperfbc]

Re: Penta 270 Troubleshooting

EDIT: nevermind, I see now.

Thanks. Local shops says they probably have a replacement in stock for about $25. Does that sound about right?

 

[thumperfbc]

Re: Penta 270 Troubleshooting

Just pulled the impeller... Real easy.

Now, I am no expert, but this doesn't look good to me.

Anybody have a part number?

 

[captmello]

Re: Penta 270 Troubleshooting

Ya, that impeller looks nasty.

I mentioned earlier I thought it was an aq190 which was the Volvo version of the 302 engine used in 1976 and 1977 only, but now I don't think so. I now think you've got a crusader marine engine.

Have a look at the manifolds and risers in this link. They are aftermarket parts but look like yours.

http://www.marineengine.com/parts/sierra_marine/catalog.html?http://www.marineengine.com/parts/sierra_marine/crusader.html

Unfortunately they don't list any impeller or raw water pump parts.

Maybe someone else knows how to find the right impeller.

Here is the Volvo pump, it does look very similar, just can't say if its the same.

http://www.volvopentastore.com/Sea_Water_Pump_835585/dm/*******.741616813--**********.207122738--store_id.366--view_id.316960

Good luck.

 

[Maclin]

Re: Penta 270 Troubleshooting

Regarding the thermostat, it may be in the top of that housing and not laying right in the manifold like you would expect if you were working on a car.

 

[Howard Sterndrive]

Re: Penta 270 Troubleshooting

all 4 pieces are VERY corroded.

btw, eveything looks like new to me.
hard to tell from pics, but I can't see much of a corrosion issue on the pipes.

 

[thumperfbc]

Re: Penta 270 Troubleshooting

btw, eveything looks like new to me.
hard to tell from pics, but I can't see much of a corrosion issue on the pipes.

The insides of the hosing was quite bad. The outsides don't look bad at all.

I purchased new hose and a new impeller today, will get everything back together tomorrow and hopefully run it out the river for a try.

Thanks guys!