Pontoon Boat & Deck Boat Forum

My transom is crap on my pontoon so Im going to need to fix it . What I want to do is move the gas tank to the transom which would allow a little better balnce and move a little weight forward. Heres my plan , use the current transom as a nose cone and add 3 foot to it . Its going to have a flat bottom roughly 15 inches wide angling up . I want to enclose it and add a bilge and live well pumps and of course ill have to put a drain plug on it for when its on the trailer . My only concern is that it is going to mess up the boat handling with the extra flotation in the rear. I notice on the new toons with large rear transom they are ope so they fill with water when stopped .

Have any of yall done this .

BTW the boat is a 24' tracker party barge with a 75hp merc on it . I need to fill out my sig

Can't help you with the transome but how do you run a 17p prop on a 75hp motor? And a 4-blade no less.

cwag911 wrote:Can't help you with the transome but how do you run a 17p prop on a 75hp motor? And a 4-blade no less.

Slowly?
I'm betting it doesn't get more than 3,000 RPM!

The 15 3 blade I could red line the motor at 3/4 throttle , the 3 blade 17 I ran right on the red line at wide open throttle so thats when I bought a new 4 blade 17p . With just me in it I could red line it at 21/22 mph gps but with the family me plus wife , 2 kids and gear on board it hangs about 200 rpm shy of redlining WOT 19/20mph gps .

By myself , using phone as a gps by here is the speedo


The smoker at 20 6000 rpm


3/4 throttle cruising with the family note 4500 rpm which IRRC is around 15 mph

Hawk_308 wrote:The 15 3 blade I could red line the motor at 3/4 throttle , the 3 blade 17 I ran right on the red line at wide open throttle so thats when I bought a new 4 blade 17p . With just me in it I could red line it at 21/22 mph gps but with the family me plus wife , 2 kids and gear on board it hangs about 200 rpm shy of redlining WOT 19/20mph gps .

Interesting - what's your red-line RPM on that motor? Mine is supposed to hit 6,000 RPM at wide open throttle.

Edited my previous post with pics and explanations .

The 15 3 blade I could red line the motor at 3/4 throttle , the 3 blade 17 I ran right on the red line at wide open throttle so thats when I bought a new 4 blade 17p . With just me in it I could red line it at 21/22 mph gps but with the family me plus wife , 2 kids and gear on board it hangs about 200 rpm shy of redlining WOT 19/20mph gps .

By myself , using phone as a gps by here is the speedo


The smoker at 20 6000 rpm That seems awfully high! My 94 merc 115 redlines at 5250.....

My last bass boat red lined at 6000 and this boat the tach is marked red at 6000 and above .
Heres the prop



BTW I tried a 19 pitch 3 blade it would do 5500 at wot but I couldnt control the boat a low speed and I was worried about loaded . I did get it up to 25 though

Your tach has to be set wrong or you REALLY have cavitation issues. I have a beefy 2.42 ratio gear case and only run a 13 pitch prop to turn 6000rpm @ 28mph. When I had my engine on a 16' fishing boat I ran a 17 pitch at 37mph. If your getting 20mph out of it then it can't be slipping that bad so the tach must be B.O. or set to the wrong pole count.

rancherlee wrote:Your tach has to be set wrong or you REALLY have cavitation issues. I have a beefy 2.42 ratio gear case and only run a 13 pitch prop to turn 6000rpm @ 28mph. When I had my engine on a 16' fishing boat I ran a 17 pitch at 37mph. If your getting 20mph out of it then it can't be slipping that bad so the tach must be B.O. or set to the wrong pole count.

i have to agree, somethings not right. i'm running a 14 x 12 on a 20 foot fish and cruise pontoon with a 90 hp.best i've done is 27 mph (gps). a 17p would choke it down to a crawl.

It didnt make sense to me , but Ive checked the RPM with a mini tach and the mark 1 ear and its right . Now Cavitation might be an issue , I have the motor as low as I get and its hanging back a ways on the cmc trim so The motor feels like its hooking up and doesnt sound like its "breaking free" Here is how the motor sets , its trimmed up a bit here but you can get the idea and see the setting water line on the trim .


My last bassboat had a 90 hp johnson and I ran a 17 for tight water or with a load and a 19 for when I was running light or big water . When I got the pontoon boat it had a 15p 3 blade on it ,which surprised me Id figure it would have a 13 p on it .The 19 pitch would pull down the motor under acceleration , if the 17 was cavitating I would think it would be more noticable with the 19 when I tested it .

Do I see a jackplate as well????? That could be where the difference is...

curtiscapk wrote:Do I see a jackplate as well????? That could be where the difference is...

Thats the CMC trim , the motor has no trim on it .

Oh trimmed down the motor skeg is about 3 -4 inches off the ground with the boat on the trailer .

Well back to the transom and after doing some research I think Im going to make it large enough to hold my 21 gal gas tank and up two 4 batteries that I can access via door in the floor . My best friend that is a experienced TIG welder that offered to glue it together for me since I have no experience welding aluminum wants me to go all out to a 3.0 or even a 4.3 I/O settup. I want to replace the motor sooner or later anyway for a fourstoke which I/O ing it would accomplish that on the cheap compared to the price of a new 4 stroke outboard .He can get me a 3.0 with alpha drive for about 500 bucks which is tempting I also have a 4.3 setting in my carport right now ....What do yall think?