Volvo Penta 740A Overheat

Deep Elem

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Jun 14, 2010
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:mad:
I have a 1992 Regulator 26CC with a 7.4 L Volvo Penta 740A freshwater cooled with Power Steering. This April, after sitting for a month or two, the fuel guage was not working (and still isn't). We had an existing power steering leak and hydraulic steering leak as the seals were old and needed work. I replaced the rams (both of them) as the rebuild kits were darn near the cost of NOS parts on ebay. Backed her down the boat ramp and she ran great. Took for a test run and she got hot. Tightened belts, still got hot. It only gets hot after going from high RPM's to idle. Replaced belts, still hot. Pulled Raw Water pump out, (too tight to pull impeller) and impeller was intact. However the seal inside the pump housing looked damaged so i replaced the entire pump. Reassembled everything, backed her into the water and CLICK....CLICK....CLICK. No start. Cleaned battery posts and leads...nothing. Used booster pack...nothing...jumper cables nothing...Removed batteries and had Auto Parts Store Test them 12.6V each and CCA checked out. Must be the starter. Tore down Starboard riser and manifolds to get starter off and had it tested...BAD STARTER. Reinstalled, reassembled and turned key...dual battery switch set to both. Nothing and Voltmeter dropped to less than zero and stayed there for a few seconds before climbing back up. Set battery selector to one battery and the same thing happened. Set to number two battery and she started right up. BACK to the original problem I ran the boat and she still got hot just as before. Replaced thermostat today and still same problem. The next thing I was going to do was take upper gear box off and check/replace inlet pipe on drive. BUT.....I have read that another person had a similar problem and it ended up being the gauge. I have VDO gauges that are all wired together in the console. Last year I had to replace the temp sender and oil guage but evereything has always worked fine. I have put 1200 hours on her since buying in 2007 and electrical problems have been non-existent. I am wonderin if my dead fuel gauge, intermittent hot water temp readings and freaked out number one battery could be related. Today I put a stethescope on the engine and noticed a dragging noise in the alternator (new in 2008) and also noticed fluctuations in voltage corresponding to the noise. Am I better off eliminating the possible mechanical causes prior to chasing the electrical gremlin. Can a bad battery harm the gauges. Although I think it is unrelated, it is worth mentioning that my Garmin 3205 backlight does not work in daytime mode, except when the boat is being started it will flash for a nanosecond then back to being impossibly dark (but still on).
 

captmello

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Jun 30, 2008
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Re: Volvo Penta 740A Overheat

Welcome.:)

It sounds like you've got a few issues.

You can test the temp sending unit/gauge for accuracy by using an IR temp gun. Test the temp at the base of the sending unit and see if it matches the temp on the gauge.

The alternator sounds like it needs to be tested as well.

You can check the intake fitting on the outdrive by simple removing the hose. If the fitting is corroded it should be obvious. No need to pull the upper. At least to check the fitting.

The wiring issues may be related or not. I'd start by checking all the connections and cleaning, etc.

One piece of advise, when posting, keep each post to a more specific issue, don't lump everything together. I think you'll get a better response.;)

Hope you get it worked out. Let us know how it goes and if you have further questions.:)
 

Deep Elem

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Re: Volvo Penta 740A Overheat

I pulled the hose off the drive today and the fitting was not corroded, however it appears that the gasket has deteriorated and there may not be a total seal between the fitting and the drive housing. The engine gets hot even at the dock. If the fitting and hose are completely submerged, is it possible for a bad seal at the fitting to cause a problem while idling at the dock?
 

captmello

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Re: Volvo Penta 740A Overheat

I pulled the hose off the drive today and the fitting was not corroded, however it appears that the gasket has deteriorated and there may not be a total seal between the fitting and the drive housing. The engine gets hot even at the dock. If the fitting and hose are completely submerged, is it possible for a bad seal at the fitting to cause a problem while idling at the dock?

No, a bad intske fitting that is submerged in the water wouldn't cause an overheat. How could you see the intake fitting gasket? Did you remove the fitting?

You said you have fresh water cooling, so you have a heat exchanger right?

Have you back flushed the heatexchanger? Does the freshwater system include the exhaust manifolds, or just the engine block?
 

Deep Elem

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Re: Volvo Penta 740A Overheat

I could see the gasket between the drive and the fitting.

Boat is FWC including the manifolds.

I removed the end caps from the heat exchanger today and sprayed a hose from each side to the other. Seemed to be clear overall. I also put the hose into raw water feed backflushing to ps cooler and oil cooler out the supply hose at the raw water pump.

It idled for 15 minutes at 165-170. In the water I revedd it to 1800 rpm and kept it there to build some heat then dropped to idle. Crept to 180 (verified by infrared temp reader at base of sender). Slowly fell back to 165-170. Took her for a spin. Cruised two miles at 3600 and stopped... Climbed to 185-190 then dropped. Ran back to dock and parked heated there to 200-205 reved engine to drop it back to 170 range.

I noticed the temp on port riser was 10 degrees hotter than starboard. The saltwater sections on the ends of the exchanger were around 100 cool to touch. So were the SW pipes from exchanger to riser. However, in the coolant section of the exchanger.. The port side was around 155 and the starboard about 125.??????????????? Not sure if that is normal. The coolant pipes, resevoir, and thermo housing are considerably hotter than the SW areas. Appreciate your help.
 

captmello

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3,856
Re: Volvo Penta 740A Overheat

I'm not experienced enough with the closed cooling systems, we don't see them around here too much. However, FWIW, other Volvo penta engines of that same vintage, four cylinders, used hotter thermostats in the fwc engines. as high as 180-190 deg.

It sounds to me like its overheating while on plane which typically means an air leak. I would continue to test for that. You could install clear hoses that run to your rises, and see if you get air bubbles while running on plane or not.

You can't see the gasket under the intake fitting. There is a bushing below fitting that may be seen. That bushing has been said to cause air leakage as well...Is there plat in the outdrive at that point. When you lift on the drive do you see play it that gap in the outdrive just below the intake fitting.
 

Deep Elem

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Re: Volvo Penta 740A Overheat

It is specifically not overheating on plane. Only after cruising when stopped. I went thirty miles the other day and it got hot only after I stopped to fish.
 

Deep Elem

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Re: Volvo Penta 740A Overheat

The thermostat is fully open at 180 but I got as hot as 205. Thermo is brand new.
 
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