87 dt65..lower unit/prop?.. NEED IDEAS/HELP

[rogerf1970]

hi i have a pontoon that i rebuilt and this outboard. i have a mechanic background but this outboard is killing me.. it runs good but at first i thought i had a prop hub going bad, so i replaced it and all was good or so i thought, once i was able to run the boat i thought i felt prop cavitation, i have raised and lowered the unit i added a doel fin just to see if i could change anything. after several weeks i hit bottom and bent the prop, i replaced it and with the new prop i thought i fixed it, but when the unit is cold it seems to work well and the more i use it the worst it seems to get. my question is... can there issue i feel be the lower unit? it gets so bad all i can do i idle in, but the next day its alot better for a little while. any suggestion is appreciated, i am going in circles... thanks roger

 

[rogerf1970]

Re: 87 dt65..lower unit/prop?.. NEED IDEAS/HELP

No ideas from anyone?

 

[ADK_Boater]

Re: 87 dt65..lower unit/prop?.. NEED IDEAS/HELP

Describe the symptoms. What exactly is it doing...noise?...vibration?...be specific. Does it get worse with increased speed or throttle?. You said you hit bottom. Did you check your prop shaft to see if it is bent. even a slight bend in the shaft can cause real problems. Give us the full details.
Also. When you are cruising along at 3/4 throttle or so, what does your wake around your cavitation plate look like. it should be even with the plate, or hydrofoil if you have one. Take a picture of your wake right where your outboard is while yo are at 3/4 or so. Post the picture here with all detailed descriptions.

 

[rogerf1970]

Re: 87 dt65..lower unit/prop?.. NEED IDEAS/HELP

No longer able to run but over idle, 24 pontoon with a 65hp 1987 suzuki... from day one i had an issue..tilt the engine all the way down and the engine would push the boat but would not get on plane, when i trim the engine up it felt like prop cavitation (feels like prop hub about to spin out). the transom well had openings on the side and would completely fill with water and over flow the transom,so i added sides to eliminate that, that reduce 99% drag of the transom well now water runs under like normal. i have went through 3 props and the issue remains.. my question is.... is there anything in the lower unit that would slip or any clearance that can increase and create a "slip" after it gets hot (feels like prop hub about to spin out).

p.s i can run the boat cold and it almost feels normal but after 5 mins the engine warms up and i have to idle back because anything above idle the engine revs up and "neutrals out"

 

[ADK_Boater]

Re: 87 dt65..lower unit/prop?.. NEED IDEAS/HELP

That size engine is a little too small for that size pontoon boat. my friend has a 24' and he has a 115hp. Pontoon boats don't "plane" like v-hulls do. All I can think of without seeing pictures is that your motor is not mounted in the right spot, and your shaft does not reach far enough into the water when trimmed all the way down. Pics would help a lot.