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#572641 - 08/03/19 07:34 PM
Re: Does anyone have experience with a Mercruiser 4.3?
[Re: CharlesS]
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Joined: Jan 2003
Posts: 3,975
Jack T
Admiral
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Admiral

Joined: Jan 2003
Posts: 3,975
Southern California
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Like all boats, several factors determine performance. You have already mentioned displacement/HP. Some others that affect pulling power--perception of expected performance like pulling during deep water starts done by skiers and wake boarders, top speed, cruising speed, most efficient, etc.
For example 1. A smaller boat with the right engine, prop will do a great service for pulling up skiers.. A lower pitched prop will get skiers up, even with a"medium sized engine. For example, I ski Flat Head Lake in Montana now and then behind a 16 foot aluminum fishing boat with a 90 hp engine outboard. Too tall a prop may give you higher speed, but if 35 mph is good enough, then a "low gear" prop will do an excelent job. 2. Number of people aboard, and their placement in the boat. Too much weight will slow down a boat considerable. On our 17" Eliminator with OMC 3.8 litre engine worked great with a 17" prop with three people on board it was a great performer as long as they were properly spaced around the boat--except at 5000 foot elevation., when it took forever to get on plane. A reasonable planing speed like 3.5 to 5 seconds will usually do what you want it to do.. Skier skills also determine what you need. I learned as a high schooler behind a 35 hp Johnson on a small boat. Wasn't easy, but I was able to ski. 3. On and on. I think you know all this, but for other readers, it might be helpful.. 4. Fuel injection will generally give you better performance, but carbs have done the job for many years.
If you are interested in a specific boat, a water test is good to experience. Some I/O engines will have a max RPM around 4800-5000. With wide-open throttle and two people in the boat, trimmed properly, look for this range..
My personal experience is that the 4.3 in a 17' to 18' boat will do the trick for you. It's a give-and-take proposition.between speed and pulling power.
Have a great day of boating 2012 Monterey 224 FS, 300 HP Volvo Penta with catalytic converters
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#572647 - 08/05/19 01:18 PM
Re: Does anyone have experience with a Mercruiser 4.3?
[Re: CharlesS]
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Joined: Feb 2003
Posts: 11,870
Frantically Relaxing
Admiral
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Admiral
Joined: Feb 2003
Posts: 11,870
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Our Regal has 2 of 'em... 28' long, 10' beam, and they get the beast on plane nearly immediately. Caveats: It has Regal's Fastrac hull, which some folks had me believing only works ON plane- may be, but this boat planes as fast as our Chap did! Was quite a surprise-- Not sure which Volvo DP props are on it, but cruise speed, if memory serves, isl like 28mph at 3400 rpm, so they're definitely not steep props and probably a good reason for the fast plane. I believe I topped it out at 36 one day too. Only had it out twice, and didn't even use it last year, and not yet so far this year  so it's all from faded memory I have a video of us getting on plane in the thing, think I can find it?? 
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