Water splashing over transom

[StarcraftTR150]

Hi there,

I have a 1971 Starcraft TR150. It is a 15ft trihull boat with a 60hp Johnson hydroelectric drive outboard. When at high speeds, water rushes into the splash well at the rear of the boat. The water seems to be coming from the small gap between the top of the transom and the outboard. Could this be due to improper motor tilt or prop size? I have attached a video for reference. Any recommendations or ideas are appreciated. Thanks!

View attachment trim.0E18B0C0-5A30-4F5B-B393-F061436DAACC.MOV

 

[roscoe]

Likely that the motor is mounted too low.

Anti ventilation plate just above the propeller, should be a little above the bottom of the hull.
See bottom red line in the diagram below.

When on plane, the water coming from under the hull, should go under this plate, the top of the plate should be above the water.

My guess is that the water is hitting the front of the engine several inches above the anti ventilation plate.
The water deflects up and forward off the front of the engine and ends up in the slash well.

It has nothing to do with the prop.

 

[Bondo]

Hi there,

I have a 1971 Starcraft TR150. It is a 15ft trihull boat with a 60hp Johnson hydroelectric drive outboard. When at high speeds, water rushes into the splash well at the rear of the boat. The water seems to be coming from the small gap between the top of the transom and the outboard. Could this be due to improper motor tilt or prop size? I have attached a video for reference. Any recommendations or ideas are appreciated. Thanks!

Ayuh,.... Welcome Aboard,..... Ask yer question only once, in only one forum,....

thank you,....

 

[Poormansboating]

I personally have never used one or owned one but I have a few boating buddy's to that swear buy using jack plates. They say they are amazing. May help in your situation. For me they cost to much seeing I've never had a issue without them.

 

[ahicks]

Long shaft motor installed on a short shaft (15") transom?

 

[Poormansboating]

Would a jack plate help with his issues

 

[ahicks]

I'm not a big fan of patches, which is what a "jack plate" would be if installed to lift a long shaft motor installed on a short shaft boat, especially when talking about something the size of this boat.

Jack plates enable an incredible ability to run in shallow water and are very popular used on performance (big dollar) fishing boats used in areas with shallow water (Gulf Coast). They can be pretty impressive to watch when used properly. They lift the motor WAY up, which can produce quite a roostertail while running through really scary shallow water. Sometimes a little shallower than what the driver realizes - producing catastrophic results. A boat moving at the speeds these guys are running, if they hit an oyster shoal, those shoals are hard as a rock, producing fairly predictable results......

To be considered I think, is the weight of something like a jack plate when used on something like a 15' runabout. Another thing to consider might be the leverage placed on that transom. It's darn sure not being used as designed.

I wouldn't do it....

 

[Alumarine]

Do you have a depth sounder transducer installed on the transom?
They can direct spray upwards.

 

[Poormansboating]

Yeah I never run one before alot guys around here use them in there bass boats and swear buy them.

 

[Poormansboating]

I have even seen some use them on small alluminum boats with 25hp

 

[WesNewell]

It appears the engine is mounted as low as it can be. He doesn't need a jack plate. He just needs to raise the mounting bolts 2 or more holes to get the lower unit higher and the av plate even or slightly higher than the bottom of the hull line. When done, he will also see an increase in top speed and higher rpm's because there will be less drag from the lower unit. It may be enough that he could increase prop pitch and gain even more speed. I'd say he could gain 10-20% in speed if done properly.

 

[Sea Rider]

If the water spray at speed is seen even round the front lower leg as seen from inside the boat, that's due because the water flow exiting the outer middle hull is banging hard against the non edged portion located above the upper water deflector plate.

Whatever need to do, modify, etc sit the motor bit higher on transom for the hardened water flow to skim under the upper edge found right under the small upper deflector plate to fully cancel that situation. Visually test and check under trial and error different motor heights positions till the out splashes are fully canceled.

Happy Boating​

 

[Texasmark]

Several folks nailed the problem. Looking at the picture the Anti Ventilation is the black line just above the prop. It stops at the leading edge of the mid section. The next black line above it in the picture is the water deflection plate that sticks out roughly an inch "ahead" of the mid section. On your engine mounting apparently that plate is below the water that rushes out from under the transom when up on plane, and as a result runs up the leading edge of the midsection and into the boat...... supporting what all the other guys said, your engine is mounted too low!

 

[StarcraftTR150]

Hello everyone,
Thanks for the info. I looked at the motor and it was indeed mounted as low as it would go. I was able to use a floor jack to raise the motor up two holes and level the cavitation plate with the bottom of the hull as suggested. My motor is now floating above the transom where it use to hook over the lip. Will a block of wood in this gap suffice? Picture for reference of the gap

 

[racerone]

No need for a block of wood there.

 

[H20Rat]

Those hooks are just there to make your life easier when mounting the engine. They aren't meant to be long term structural, all support is through the mounting bolts. Go boating and don't worry about it!

 

[Stinnett21]

Please report back on your outcome.

 

[StarcraftTR150]

View attachment trim.DC688ACA-1E78-4927-AA53-45B8E769AF89.MOV
Problem solved! Thanks everyone

 

[R.PREMER]

View attachment 344065
Problem solved! Thanks everyone

 

[R.PREMER]

If you dont mind me asking how did you solve the problem?
mine sprays water on the motor really bad.