V175 Gas consumpsion and temperature

[HORACIO]

I was running and metering for first time my motorboat and the following figures arises. Engine Mariner V-175 serial number corresponding to 8058870_UP INT fited on boat reaching about 5600 R.P.M. at W.O.T. Sailing @ 4000 R.P.M. gas cons. 11 gallons/hr, speed about 27 milles/hr. Engine water temperature less than 110 F. degrees. I`ve been reading that normal cons should be power/11 = gallons/hr. But, first, what power is suspected for this engine at 4000 R.P.M.? and second, that water temperature seems to low to me. What shoud be the normal temperature for this kind of engine?
Tks in advance.
Horacio

 

[Silvertip]

Re: V175 Gas consumpsion and temperature

11 gallons/hour sounds very reasonable at 4000 rpm. Outboard engines tend to consume fuel at a rate of about 10% of their rated horsepower at wide open throttle. So at wide open throttle, your engine would consume roughly 17.5 gallons/hour, not 11 gallons/hour. This of course depends on the type of hull,. watter conditions, load, etc.

 

[HORACIO]

Re: V175 Gas consumpsion and temperature

Silvertip thanks for your input. I agree that cons. seems about normal but I supose that relationship power vs. R.P.M. is not linear so I`m not sure about that. Furthermore I remember something about "propeller law" and relationship should be exponential insted linear. Beside, what about temperature, don?t you think that is so low? I was especting about 175 F. degrees. Thanks for your time.
Horacio

 

[emckelvy]

Re: V175 Gas consumpsion and temperature

175 deg is way too hot for a 2-stroke. 125-135 deg max is more like it.

When you're running at a fast clip, water pressure will force the "poppet" valves open, and cooling water will flow freely thru the block, bypassing the thermostats.

The thermostats only come into play at low speeds and idle. You want a nice, toasty-warm engine at idle 'cause a cold one doesn't idle so good. But at speed you need lots more cooling so she don't burn up. Thus the spring-loaded poppets. Note that when servicing the cooling system on motors using thermostats and some kind of additional pressure-relief (such as poppets), you should inspect/replace impeller, thermostats, and poppets. They all work together to keep your motor from becoming one big melted lump of aluminum!

BTW the HP/10 rule applies to Full-Throttle fuel consumption only, on a crankshaft-rated motor. Cruising GPH will vary widely by hull/prop/setup/etc and is a lot harder to predict. A GPH meter would come in handy in this case, or use a portable tank to gage how much you're using.

Note that later-model, prop-rated motors will use even more fuel than the HP/10 rule. Divide by 10 then add some more!! At least fuel prices are down, Yippee!!!

HTH............ed

 

[HORACIO]

Re: V175 Gas consumpsion and temperature

Thanks for the reply, I was forgetting about the poppet valve. That remembers to me that when I bought the boat intake water strainer was 50% blank with epoxi to possibly get a warmer engine when cruising. I?ve cleaned up that stuff because seems to risky to keep it that way. So, cooling system should be working fine and this low temp. is normal, yes?
About consumption I?ll try to metering with a portable tank to find out the gas rate lines at diferents speeds.
Horacio

 

[j_martin]

Re: V175 Gas consumpsion and temperature

Thanks for the reply, I was forgetting about the poppet valve. That remembers to me that when I bought the boat intake water strainer was 50% blank with epoxi to possibly get a warmer engine when cruising. I?ve cleaned up that stuff because seems to risky to keep it that way. So, cooling system should be working fine and this low temp. is normal, yes?
About consumption I?ll try to metering with a portable tank to find out the gas rate lines at diferents speeds.
Horacio

I think it should be a bit warmer. It'll tend to seize on sudden power increase if it's too cold, just because the pistons expand rapidly and the cold block could be a little tight.

You still haven't told us what kind of boat this is on. Sometimes the upper water intakes are plugged with epoxy because the motor is run high enough on the transom, or jack plate, to lift them out of the water. On some boats, that's where they run the best. Half the intakes are plenty on a 4 3/4" lower unit, which would be what you have. The best watch on the situation is a water pressure gauge.

Check the water temp at the tell-tale when it's idling. Doesn't make any difference what the engine temp is, the water should be at the t-stat temp at the tell-tale. All the water that gets there has gone through the t-stats. If it's cool, the t-stats need attention. Should be around 140 degrees.

If the water pressure at mid range is too low, and there is plenty of water flow, as in a cold engine, the poppet valve needs attention.

A bad water pump will always make it overheat, not overcool.

hope it helps
John

 

[HORACIO]

Re: V175 Gas consumpsion and temperature

I think it should be a bit warmer. It'll tend to seize on sudden power increase if it's too cold, just because the pistons expand rapidly and the cold block could be a little tight.

I agree 100%

You still haven't told us what kind of boat this is on. Sometimes the upper water intakes are plugged with epoxy because the motor is run high enough on the transom, or jack plate, to lift them out of the water. On some boats, that's where they run the best.

That`s was i figure and ask to mechanic about that. He told me engine position was o.k. but A.S.A.P. I`ll post pictures about that.

Check the water temp at the tell-tale when it's idling. Doesn't make any difference what the engine temp is, the water should be at the t-stat temp at the tell-tale. All the water that gets there has gone through the t-stats. If it's cool, the t-stats need attention. Should be around 140 degrees.

If the water pressure at mid range is too low, and there is plenty of water flow, as in a cold engine, the poppet valve needs attention.

tks for your imput I`ll pay atention to that at first time posible.
Best regards Horacio