Pontoon Motor Height

[C_Curran]

I have a 89 Party Barge 24' with a 115 Evinrude, I have the motor running great but at wot im getting a lot of water over the transom and up the sides of the motor, if i trim up much at all it blows out and have to trim back down. Would raising my motor help this or hurt, my toons sit pretty low in the water and my motor is mounted all the way down.

 

[HotTommy]

On a typical pontoon boat, the motor is mounted to the transom that is the aft piece of the motor pod, a small triangular shaped pod roughly level with the pontoons at the aft center of the boat. The rule of thumb for the starting height of the motor is to have the motor's anti-cavitation plate level with the bottom of the motor pod.. Some splash is normal. But if the boat sits very low in the back, it is likely because there is too much weight toward the back. For example the motor may be heavier than the one originally envisioned for this boat. ... Note that trimming the motor up will make it try to push the back of the boat lower.

 

[C_Curran]

The coastguard rating for the boat is a 115, I realize that most motors sit right on the transom, but because of the way my boat is layed out I was just curious if it woukd help to raise the motor or would it be worse

 

[HotTommy]

If you can raise the motor without raising the anti-cavitation plate above the bottom of the engine pod, give it a try. It might make a positive difference. .... But also look at managing the weight on the boat. For example, have passengers sit forward rather than aft, or move the battery farther forward.

 

[C_Curran]

Is the engine pod considered the bottom of the transom? Does that mean, Don't raise the anti-cavitation plate above the transom?

 

[HotTommy]

The transom is on the back face of the pod.

When moving, water goes under the pod so the propeller has to be low enough to get an unobstructed flow. BTW, note from this image that water pushed up and away by the inside surfaces of the pontoon will tend to splash toward the engine. The deeper the pontoons are in the water, the more you'll see spash back there.

 

[ahicks]

Agree with Tommy. The issue is just as much about how low that boat is riding in the water, likely due to engine weight, as it is about the motor's location on the transom. Also agree with the idea of raising the engine as an attempt at improvement/ partial cure.

 

[Sea Rider]

Is the barge often or always used loaded with some passengers, many passengers ? Try distributing the load evenly on deckf or the toon to ride parallel to water level, check on flat calm water cond if the motor still splashes water up transom. Post your findings..

Happy Boating

 

[C_Curran]

I decided to raise my motor and it stopped the prop blow out and gave me about 2 to 3 mph top end. I'm gonna try going one more hole up and see how that works. I'll post results, thanks for all the replies. God Bless

 

[Sea Rider]

With motor trimmed to 90 deg along a well deck weight distribution, the ideal motor height setting for any toon is when water flow skims right under the upper plate.. That spot achieves the best prop thrust. Once there can go towards a prop maximization if needed.



Raise or lower the motor on transom accordingly to achieve that condition. Must visually check what's going on at back motor when playing with different motor heights, ear sound testing is no bueno nor exact.

Your previous water splash issue was due to water flow was banging over the upper plate and not under it where the sharp edge cuts nicely the flow and diverts it backwards like in pic. Water splashes side of motor or even over transom ones will create unwanted water drag on toon associated with rpm and speed reduction as have noticed.

Report your findings if the toon performed much nicely at that precise height setting...

Happy Boating