Need help with 1994 yammy v76 250

[JrMako81]

Hello everyone. So recently father and I purchased a 26 Mako with a yammy V76 250 hanging off the back of it. On its first trip it wouldn't pass 4000rpm so that week I replaced the fuel from tank to motor including primer bulb, 2nd trip still same, replaced plugs and did a power tune through the carbs and tightened all the carb linkage which was loose also checked compression and all cylinders are at 120, 3rd trip now I'm at 4600rpm at WOT. Also primer bulb won't hold prime for more than 2 to 3 min but it does get solid when primed. Motor starts and idles great and I can run 4600rpm all day with no hiccups. Any ideas on what can be holding me back from 5500 rpm????

[99yam40]

wrong prop maybe or set up, hard to tell with what you posted.

Did the motor ever run higher RPMs set up like it is?

[JrMako81]

According to the PO the boat always ran this way, but he didn't strike me as the type of person to care about how it ran as long as it got him from point a to b he was happy. What other info would you need to better help me??

[99yam40]

Prop size and pitch
what holes it is set in( how high the motor is set )

Look here and see what a rig like yours should run and with what prop they used
Performance Bulletins | Yamaha Outboards

[JrMako81]

Ok ill check that this afternoon when get home. Thank you

[JrMako81]

This motor is carbureted, it could it be that the carbs are out of sync??

[JrMako81]

Size and pitch I'm not sure of yet but the motor is on the top hole and the transom was cut a additional 3-4 inches. This is an X Marine Patrol 1991 Mako 26. It was rigged with twin 250, you can still see where they filled them in.

[99yam40]

Could be it is just way under powered and/or over propped.
Look through that link I posted to see if you can find a 26 with a 250

[ausnoelm]

Seeing as it was originally rigged with twins, my guess is they kept one motor (after the other one had problems?) and had to cut the transom, because the shaft would have been too long, and they kept the old prop, and coming from a twin setup, it is just too big, you will have to test a much smaller one.

[JrMako81]

ok, so i get home and pull off the prop and i have a Stiletto Advantage II 14 1/4 X 17

[99yam40]

so have you spent the time to look at the web site I posted to see what prop they used on a rig like yours with a singe 250?
if they show a single

[JrMako81]

I did, and the only one with a 250 has 2 of them and they r running 15 1/4 X 19.