Raised Motor - Get Spray from cav plate?

[atengnr]

I raised my johnson 68 55hp and noticed that there is a spray coming off the motor left and right about a foot high. It appears as if water is being deflected off the ant cav plate. Does this mean the engine is too high??

Boat ran about the same speed as 1 inch lower.

Thanks.

 

[hwsiii]

Re: Raised Motor - Get Spray from cav plate?

Atengnr,welcome to Iboats prop forum and we will try to help you as much as we can, but there is certain information that is needed in order to help you. When we get information in bits and pieces we are continually having to look back and forth to try and piece the information together. The following form has all of the information that is needed to help you with your problems in finding the right prop. If you do not know all of the information that is asked for on the form please give us the most information you have available as I have a program I designed to find the right prop for any planing hull boat that needs this information, and most other people who are trying to help you will need the same information. It requires time to find all this information when we have to look for it and in my defense I expect you to be willing to expend as much effort in finding the right prop as I do. We hope to be able to help you get the exact prop you need for your particular uses, and this information is required to do that.
It is not as simple to pick the right prop as most people coming to this forum think it is, that is why we ask so many questions, it is for your benefit we ask all these questions. And if you have a stainless steel prop or are changing to one the blade geometry of the prop can make a lot of difference in speed and RPM.

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make and model of motor
7. HP and gear ratio of motor IMPORTANT
8. Manufacturer?s recommended WOT range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from prop, how much gas and how many people in boat for test data

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.

H

 

[atengnr]

Re: Raised Motor - Get Spray from cav plate?

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make and model of motor
7. HP and gear ratio of motor IMPORTANT
8. Manufacturer?s recommended WOT range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from prop, how much gas and how many people in boat for test data

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.

H[/QUOTE]

Thanks for the reply.

Boat is a 1968 safetmate 16ft with newly rebuilt 1968 johnson 55hp (4500-5500), spinning a 13.5 x 15 prop

Boat weight is unknown, but I would estimate 800 lbs (without passenger)

Not a deep v

As far as speed, the boat hits 29 mph. This is only about 2 mph less than the 1988 60hp engine I had on it previously. I dont have a tach, but based on the testing I did with the 60 hp back in 06, this is probably around 5400-5500 rpm (I had the same prop on the 60hp at first).

I am wondering mostly if the spray I am getting indicates that I should raise it up one more notch...

 

[junior1113]

Re: Raised Motor - Get Spray from cav plate?

needs to go up more if cavitation plate is causing spray. hwsii can get you close with a size. rpm is very important to know. suggest getting one. your motor life depends on it.