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Mercruiser 3.0 ,2010

Thanks for the feedback.When I repowered I ran new fuel lines, additional (new) fuel tanks ,and of course new filters. I will follow the august advice of you all.Gradual (very slow) throttle increase functions well so perhaps indeed the underlying problem is restricted fuel flow.
 
searayray said:
Thanks for the feedback.When I re-powered I ran new fuel lines, additional (new) fuel tanks ,and of course new filters. I will follow the august advice of you all.Gradual (very slow) throttle increase functions well so perhaps indeed the underlying problem is restricted fuel flow.
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How did you plumb these? Do you have selector valves to choose which tank you want to use?
 
I do have selector valves. Port and starboard each have a dedicated outboard tank and can share the main (center) tank. To anticipate your next question; Yes the problem occurs no matter the tank selected.I have not yet studied the "new and improved" cold operating mercruiser employs, but I know it is not the conventional electric choke as before. I wait quite awhile for the engines to slow down to an acceptable rpm (800 or so) before I get underway. The engine in question does not stall when shifting, it waits until I'm leaving the channel to act up. Speed changes after I have been running for awhile do not seem to be a problem.On returning to the launch ramp I still have the issue of stalling on that engine. The entry channel is long enough to allow the engines to cool down to minimum operating temperature (165+-).While underway that temperature is not noticeably higher but it must be high enough to affect the engine operation.
Thanks again for the help. Ray
 
Gear ratio is duly noted. I did reprop to account for the difference in horsepower/torque.I will be installing floscans in the future to get a more accurate tach reading along with the other benefits.My first thought upon noticing this problem was trash in the carb, but I am not currently running the boat so I wanted to get more opinions and perhaps a simple (nice thought) solution. All of the advice so far has been very helpful.I'm a fair "wrench" but I do tend to decide I know what,s wrong and ignore other issues. After the holidays I will begin the fix.
Thanks for the help so far and I will report the results of the investigative process and the fix.
Ray
 
I'll hold off on the compression test for a while, thanks anyway. The horsepower difference is not so great. The 470's were allegedly 170 hp and the new 3 liters are 130. The real difference is that the 3 liters are hp rated at the prop as opposed to the 470's rated at the crankshaft.The horsepower rating of the 470 was considered a liberal estimation favoring the higher side. The torque on the other hand (I don't know the value) would seem to have been somewhat ,if not significantly higher. The result of lower torque means "don't pull hole shots" a wise idea. If both engines were exhibiting the same behavior I would consider that I was over propped. Slow and steady gets you to the fish or something like that.
Ray
 
In 1985 and 1986 the four barrel 470's were called 190's and horsepower was rated at the crank rather than the prop. I guess sometime after that they decided to change the way I/O vs. Outboards were rated and in the end made both rated at the prop. I believe that the outboards rated horsepower was always at the prop unlike the I/O's In 1987-1989 the four barrel version of the 470 became the 3.7lx 180hp which was the determined horsepower developed through the drive and at the prop. I guess a drop of 10hp. As for the two barrel versions, I think there is 170 and then 165 respectively. I think the hp rating dropped 5 hp with the two barrels. You said the 3.0 engines produce 130 horse at the prop so you have a difference of say 35 horse with the two barrel 470 and around 50 horsepower with the four barrel. Note these hp ratings were done with engines that had points and condensers,rectifiers,no electronic igniton so there may be a few horse to gain with all of the upgrades. You mentioned torque. I read a thread awhile ago by an old timer and he stated that max torque was attained at around 3800 rpm if that helps. However, I have searched high and low to find any information about maximum torque output numbers . Are you sure you are getting enough fuel to that engine with all that plumbing and water seperator you got on there. Also, the ratios for the 470 vs. the 3.0liter are different as you know already. Are you able to attain wide open throttle with the engine that runs properly? Just trying to stir up ideas that's all. Hope you get it working, best of luck, Tom
 
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Tom,
Good information. My boat and original engines are 1978. The HP rating was at the crank with about a 10% drop to the prop.After reproving I am able to run in the 4400 to 4800 rpm range. (Factory recommended). Keep stirring,I started the thread to open my mind and I'm being generously rewarded with wise counsel and helpful information.
Thank you all for your help.
Ray
 
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