Motor question 9.9 to 15 hp 4 stroke

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Originally Posted by wicklundrh

As an example, Mercury makes a regular 9.9hp motor. They also produce a 9.9 Kicker motor. The gearing in these two motors is totally different as is the prop. The same is true for Yamaha (although they call theirs a 9.9HT or High Thrust). The gearing is totally different as is the prop. On my boat, the maximum speed I can get out of my 9.9HT is 5mph. If however I had a regular 9.9 motor, I suspect to be up in the 12mph range. And that is on an 18foot deep v

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That's an excellent point! Sailboats use the high thrust for motoring around in marinas, so they are a common thing to find with those gears.

It is just a plain 9.9 tiller steer 9 pitch prop the blades are in pretty good shape do have some flat spots on the very edges of the fins like it rubbed a rock or two in its previous life.lol
My boat just seems kinda heavy in my mind I think it is a 93 model. I do want to pull the floor up 1/2 inch ply carpet covered as there is alot of debris in the runners on the bottom I would like to wash out and do some weight transfer stuff like get the batteries up front or at least to the middle it has 2 batteries but only use them when on electric only lake and both trollers one on front one on back guess I could take the rear one out when using the gas motor

Attachment 351221 moved my battery temp placement to see I'd that changes things and removed the rear battery now just gotta get to a water hole to see if it helped me any

Attachment 351222 also this is the prop a little flattening on the fins but I know a little means alot especially on these smaller engine may have to replace it also

You might want to consider replacing with a 4 blade, a 4 blade helps provide stern lift and easier planing. I put a 4 blade on my 17ft with a 40 hp yamaha and it's like a totally different boat now, I have had the same results with prop changes on the various bass boats I've had over the years too. Having the right prop is a crucial thing to performance.

After some checking one blade on the prop was bent slightly I straightened it the best I could so they all tracking straight now untill I can gather some funds for a new prop. Also ran a compression check both cylinders are carrying just at 90 lbs after 5 pulls on the cord . Seems just a touch low . And I added a homemade hydrofoil just to see if that helps me out . I do have a chance at a 25 hp suzuki 2 stroke from the mid 80s fella is wanting 500 for it as always he said it was just gone over by the local marina new pump and plugs. So that maybe an option also.
I'll let ya know how things work out as soon as I can get it on the water. Hopefully this week ...thanks for all the advice

I had a 1436 with a 15 4 stroke mercury and it was slow as all get out, sold it found a 2 stroke 25 now it runs low 30's, with a boat that big best thing to do would be find a 2 stroke 20hp or larger.