Evinrude 85hp, plane issues, too heavy for boat? top speed etc

[heckhole]

Have a mid or late 70s Evinrude 85 on my 16' King Fisher with an OMC jackplate/trim setup.

When the boat gets on plane, I can hit 41mph on GPS at 4600-4800 rpm.

Sometimes it feels like it takes forever to get the nose down and the boat on plane. I usually start with the trim fairly high and slowly bring it down, let the bow bounce once or twice and tap the trim down a touch and she will scream across the lake. Am I taking off wrong? I have no trim gauge.

Also, I've been told 4800-5500 is the ideal rpm range. I don't want to be near 5500 but Im not opposed to getting it up over 5000 for a little extra fun factor. Is this a prop issue?

I also feel like the motor is too heavy for my KingFisher. When the boat is attempting to take off, the bow soars up in the air and takes in a ton of water over the hull (bilge will pump out a gallon or two easily I'd guess) would it help to find a way to move my dual Optima batteries up to the bow some how? I've never been able to verify where the cavitation plate sits with the bottom of the boat either, the boat/trailer sit very low on the ground and I can't set the motor parallel on land to verify. The waters I fish are murky and it's not possible to check out there either.

Should also mention I'm 220lb and my fishing buddy is 325 so we are putting well over 500 lbs right there at the back of the boat, I'm sure that is not helping?

Last year I had a lot of starting issues, battery issues and more. I took everyone's advice from here and as far as that goes, all of those problems have been solved and the boat has finally been reliable and a pleasure to use.

I do have one more issue with using reverse. If the prop gets loaded with weeds and I try to spit them off with reverse, the motor will not go beyond 1800-2000rpms . Is this normal?

 

[interalian]

I'd try launching with much lower trim if you're getting water over the stern. And maybe don't sit in the stern?

Throttle is limited in reverse - normal.

 

[heckhole]

Lower trim works, I don't have a gauge so it's a little tough to tell at times without sticking it in the mud.

As for the RPMS, what can I do to maybe squeak out another couple hundred?

 

[interalian]

Propeller. What's your pitch? I'm no expert, but if say you're running a 19" pitch, a 17" will pick up 2-300 rpm. There's a prop forum - that's where the experts live. A lower pitch will pop you out of the hole quicker too.

As for trim, I usually hit out of the hole trimmed all the way down, and once the boat starts to pick up some speed raise the trim some more. Once at full chat, trim up until some porpoising, then back down until it stops.

 

[heckhole]

I have no idea what the prop pitch it. The current prop is not in great shape. It was chunked & chewed up with a ton of burs, I hit it with a file to smooth it out and it rid of a ton of vibration and seemed to pick up about 100rpms consistently.

When I trimmed fully down & hit the throttle, it only took a few seconds to get on plane, then I'd wait for the first hop and find the sweet spot trimming up. I'd like to get my family out on the lake to pull them around on a tube - but it'd be nice for the boat to be a little more capable before I do so.

 

[interalian]

A dinged up prop is not your friend, especially if it had a "ton of vibration" and probably still does have some after filing. You're not doing your lower unit gears any favours with vibration or with uneven thrust on the individual blades. Pitch and diameter should be stamped along the center diameter of the propeller, and cast into the flat area around the mounting nut.

 

[heckhole]

It's not butter smooth now, the vibration was bad I would guess. The filing and smoothing just about eliminated it to my knowledge, but then again I don't know how a new prop feels. I know a new one is required. I will look at the prop today. I appreciate your help!

 

[nanuk]

could you lay a straightedge along the bottom of the boat to the engine to see where the AV plate is in comparison? no need to have a level boat.

as for bow lift, trimmed all the way down should help lift the stern out of the water, then once moving, trim to the ideal setting?

also, can you have one passenger sit farther forward?

 

[heckhole]

I got the boat on a deeper body of water and it was on plane real fast and max rpm was 5500. So it seems the body of water I generally go on is only 8-14 feet deep, a bit weedy, so I'd attribute the lower RPM, and getting on plane issues to the weeds?

But, I do have another question, the back of the boat doesn't seem to have the greatest float. Small waves have no issue coming up over the transom. Also think it's possibly weighed down by the evinrude 85. But I did notice a lot of the foam inside the boat in the back has deteriorated. Is that something I should address?