Water coming in over the transom

steve mcintire

Seaman Apprentice
Joined
Feb 10, 2014
Messages
39
I replaced the prop on my 60 HP Mariner using the same spec. that that gave me good performance last year(10.5/13/RH Quicksilver.) The 15 Ft Starcraft SS started taking on water over the transom at an alarming rate at top end,IE 5000 RPM. When I backed down the throttle to 2500 RPM I could remain on plane and the turbulence at the prop would go away. This is my first runabout and it is no secret that I love to go fast . Do I have a prop problem or a weight distribution issue. I had 1 rider and fishing gear. What am I doing wrong?
​thanks in advance.
Steve McIntire
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Usually when water comes in as you describe it is because the motor is mounted too low.
Pictures taken at the level of the bottom in relation to the motor will help tell if it is right.
The anti vent plate (just above the prop) needs to be about even with the bottom of the boat.
Perhaps in changing the prop you reset the trim.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Depending on how low that engine is seated, will neeed to raise it a bit. Does the swivel bracket have various holes so to height play with ? If so, raise one hole. If it's a fixed swivel bracket start with a !/2 inch wooden shim and test, preferably on flat calm no wind waters. Engine mjust be trimmed for boat and anticav plate to ride parallel to water level once on plane at speed provided that boat is well deck weight ballanced. Post tests results..

Happy Boating
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Determine the source of the water intrusion and get back.....leading edge of the skeg; prop wash coming off the tips of the prop.......
 

steve mcintire

Seaman Apprentice
Joined
Feb 10, 2014
Messages
39
I just checked and the anticav plate (the trim tab is on the same plate) is flush with the bottom of the boat. Is the bottom of the keel considered to be the bottom of the boat? If so then the plate is approx. 1 inch higher. Wil send picturesn later Steve McIntire l
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Height seems reasonable
Have you tried it lately?Did you check to see if the motor picked up a garbage bag or something?
Is the bottom clean and smooth? No odd dents or anything?
Is the motor well secured to the transom?No loose parts?
 

steve mcintire

Seaman Apprentice
Joined
Feb 10, 2014
Messages
39
This craft is a 1985 model that has not been taken care of. Lots of scratches, a few dings and dents. Nothing major. What baffles me is that I had her on the water all last year and I never noticed a problem. Last years prop took a pretty good beating. It was my first year at the wheel .After reading the responses I have tried to look back There was some cavitation and the craft did some plowing before reaching plane It seemed to me that water was boiling up between the transom and the motor and was coming up on the starboard side. I will be on the water tomorrow to check things out.
thanks for all the input...
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Plowing is bow too far down wetting most all of the hull and making steering awkward. Additionally, to do this the engine is tucked in too far and this may be the cause of your problem. However, the little plate I mentioned that is an inch or so above the AV plate, protruding from the front of the LU should prevent water from running up the leading edge of the LU/midsection and into the boat. A dinged up prop with no cupping could cause cavitation but it would not cause water to enter the boat. It would/could affect the rpms (increase with slight loss of propulsion) and otherwise probably wouldn't be detectible.

Ventilation on the other hand can be caused by the prop trying to get the boat on the water and having too much resistance (being tucked in too far aggravating the condition) so prop induced water pressure/air intake takes the easy way out....up and to the surface aka ventilation. Cavitation is associated with the blade edges and area around them and is caused by low pressure sucking the air out of the water, not sucking air from the environment...aka ventilation......learned that distinction on here after referring to "the plate" as an anticavitation plate my entire boating life.....but that's beside the point.

In a lot of cases the proper position of the engine vs the hull is perpendicular to the line of the hull....at a right angle...90 degrees. On tiller operated boats it usually requires tucking in to help in getting the bow down with the added stern weight of the operator being at the engine. On pad boats and fast planing hulls like bass boats, it's usually pushed out significantly at top speeds.

Referring to your comment about plowing, if you are tucked in too far or have too much weight forward you are indeed/could be plowing. My definition of measuring plowing would be on plane at a good clip, like 30+mph and the boat is roughly parallel with the water's surface, the spray comes from well forward along the hull and as stated, the steering is impaired somewhat. If you have/had PTT, pushing the LU out would raise the bow, the spray origin would move back toward the stern, the speed and rpms would pickup, the boat would seem to float somewhat and the helm would get light, like it had power steering. For the LU to be too far out, the engine rpms would increase disproportionally and the boat speed would drop off from where you were before pushing too far out.

I just re-read your initial input on this post and it suggests the engine is too high. Being on the right side would be normal for spray generation as the prop turns cw as viewed from the rear and the output would be closest to the surface at the center and in exiting it would be to the starboard (right) side of the transom looking forward.

With the keel being significant as is the case with Starcraft and other aluminum boats, you have a mechanism for pre prop disturbance that glass boats don't have......the keel protects the area where the two hull halves are joined at the center.....glass boats are molded with a complete hull so no joint exists that requires protecting.

So, what has changed since the problem didn't exist? Shooting from the hip, I'd say you diddled your tilt or trim if you have it and the LU is tucked in too far. Or how badly did you ding up your prop....or some of both?

How about a couple of pictures with the engine in the position where you experience the problem. One to be taken from the side of the boat showing about half the boat and the engine taken from about 3' off the ground (center side height of hull) if the boat is sitting on your trailer, and another closer in, still 3' off the ground , still from the side but move in closer to the boat and partially aft of the transom so that we can see the hull outline at the transom at an angle from the rear and the engine height simultaneously.
 
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