1996 Bayliner 1600 LS - Slow!

addysdady

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Jul 24, 2016
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I recently purchased a 1996 Bayliner 1600 LS with a 75hp Force motor. The motor seems to run fine but the problem is that it?s slow and has trouble getting on plane. With WOT throttle I can hit 21 MPH @ 4900 - 5000 RPM?s. I have read that others are seeing 30mph + with the same configuration. I have two questions that I am hoping someone can help with.

I tried to add a hydrofoil to help with the planning issue. I purchased one that was made for 50hp+ outboards. When trying to install, it did not seem to fit right. I have read that Mercury used a smaller lower unit on this motor. Should I purchase a smaller hydrofoil?
The prop that?s on the boat is in rough shape. Much of the paint has worn and one blade has a slight bend. It?s currently 10? 17P. I was thinking of purchasing a 16P prop. How will this affect performance?

I appreciate any advice or guidance. If all else fails, I?ll just throw the mother-in-law overboard to lighten our load.
 

Jiggz

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Oct 23, 2009
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If you are reaching 5000 RPM at WOT, make sure the boat is trimmed properly and not plowing into the water. Also speed also depends on how much load is in the boat.
 

addysdady

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Jul 24, 2016
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Thank you for the reply. I think that I'm trimmed properly but maybe some more "trim tests" will be helpful. We have been fully loaded on most trips out but even when it's just my wife and I, we have trouble getting on plane. We'll get there but it'll take a while. Combined we're a little over 300lbs.
 

Jiggz

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You might want to check the idle air fuel mixture screw settings also. This should be around 1 - 1 1/4 turn out or even at 1 1/2 turn out from lightly seated. It does make a difference on how soon the engine gets out of a hole shot, which is basically going into a plane.

And lastly, you want to check that you are firing on all cylinders. But if you reach 5000 RPM, that is an obvious indication you are firing on all cylinders.
 

jerryjerry05

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May 7, 2008
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Does it seem to kinda slip or rev up when up on plane?
​You have power trim?
The prop needs to be in good condition.
Try bending the ear with a hammer and a block of wood?
Maybe send it away for a rebuild?

Do a compression test.

The 70 and 50hp lower units are about the same size.
The hydrofoil could slow you down some.
While it helps getting on plane it also adds drag.
 

addysdady

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Thank you all for the advice. Looks like I have some work to do. I will report results. After some more research, I have found others reporting the same issues.
 

addysdady

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So I added a hydrofoil and proceeded with a few of the tips above. The boat seemed get on plane a little faster and run a little smoother. Got up to 23MPH @ 5200 RPM which is a new record for us. A strange thing happened at the end of our day. I turned the boat around to head back to the launch and it just wouldn't speed up after the turn. Adjusted the trim and stopped and started again but it just wouldn't gain any speed. I could only hit 4000 RPM. What could have caused this change in performance? A new prop is on order. Not sure if this will help with our issues.
 

roscoe

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Oct 30, 2002
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Got up to 23MPH @ 5200 RPM



These numbers just can't be right. I used to run similar bayliner with a 70 Force. 5300 rpm and 35 mph.

Either your tach is wrong and you are only running on 2 cylinders, or your speedo is wrong, or both.


That 75 does not have a "small" gearcase. It has the same gearcase as most Mercury 50-60-70 hp motors.

They did put a larger gearcase on the 75, for the last year of production ( 1999 ) because they were trying to use up old stock in the warehouse.


Time to do a spark and compression test.

What does the tach read at idle?
 

addysdady

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Jul 24, 2016
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This is my whole concern. I thought that I should be going faster than this or at least have consistent performance.. The speed is accurate as I was using GPS. Idle usually runs around 1200 RPM's give or take. I will try to borrow a compression test and report back - this is something that I have yet to do.

I will also report that sometimes there is ventilation issues going into tight turns..... will this have an effect on performance afterwords?
 

CV16

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Aug 30, 2007
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You need a prop in decent shape before trying to figure it out. Trying to bend it yourself isn't going to do it. I'd buy a new one and have the old one fixed for a spare.
 

roscoe

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I seriously doubt the tach is right.
Idle should be about 800. So at least at idle, your tach might be off by 33%. If consistent, then your wot rpm would be closer to 3500, which would be about 22 mph.
Would also enforce the possibility that you are not running on all cylinders.

The ventilation issue will effect performance, but only slightly, not to the extent you are dealing with.

Check over all the wiring very closely.
Look for loose wires, cracked insulation, cracks or damage to the coils/cdm units.
Remove and inspect all sparkplugs, what do they look like ?

Could be 2 issues, misreading tach, and a dropped cylinder.
 

addysdady

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Jul 24, 2016
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I rented a compression tester from Autozone this afternoon. They have a free rental service if you return within 90 days. Here are my results:

Cyl 1- 105
Cyl 2 - 105
Cyl 3 - 100

Lower than I've seen others at but this was the first time I've ever done this and the engine was cold so take the results with a grain of salt. None the less, all cylinders have compression. The spark also seems good. When I removed the spark plugs, they were cleaner than expected but also felt somewhat "sticky". I replaced them as I had spares.

Slight correction, my tach shows 1100 RPM's at idle. I double checked while I was out there.

I have a new prop on order. Hopefully it will come in this week.
 

addysdady

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Jul 24, 2016
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Finally had a chance to take the boat out with the new prop. What a big difference! Boat was much smoother, faster and got on plane much quicker. I hit 26 MPH @ 5100 RPM's. Didn't have much of a chance to play with her so I am sure I could have found a sweet spot and gained a MPH or two. The old prop was a 17p and I found that these boats come stock with a 15p. I ended up splitting the difference and purchased a 16p prop. I may try a 15p in the future.

Thank you all for your words of wisdom. 26 MPH isn't insane but I can live with how the boat currently performs.
 

Arawak

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Aug 27, 2010
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I suggest you take your boat to a truck stop or junkyard and weigh it. It should go about 1300lbs plus a little extra for fuel and any accessories you have added.

My 86 Bayliner 1703 was also a pig when I bought it, and I discovered that I had soaked foam. My boat was about 500lbs heavier than it should be and the weight was mostly in the stern. Unfortunately that's not a trivial thing to address. Hopefully it's just a trim issue for you.
 

addysdady

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Jul 24, 2016
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Wet foam is a fear of mine. The prior owner had the boat on a private dock and it was never covered. There is no way that I would ever have the time to address this. The boss (my wife) has allowed me to start looking at other boats as she wants to be able to take additional friends and family out with us. We are debating a small cruiser or a larger bowrider / deck boat. I missed out on an opportunity to purchase a Wellcraft 2400 earlier this year. Loved the boat but this was prior to the wife's buy in. A friend of a friend is selling a Campion 565 OB for what seems to be a fair price. Has anyone ever heard of this boat?
 
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