Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

[89cruisers]

well after new plugs and wires, and a new axle I took the nova out today. Wasn't able to get it to go above 3800rpms and got about 38mph out of it. It was suggested trim could have been off in the previous post, I move the trim all over the place and still never got above 3800 rpms and 38mph according to the gps. To go over again what's been done, had a 302 in the boat last year hooked up to a 233 drive which is a 1.3 ratio due to previous owner taking the factory 351 out and putting in the small 302 and was only getting up to about 3200 rpms. Put in the 351 this spring, new ignition (points rotor condenser wires plugs coil), which is advancing properly, good compression, 16 pitch 4 blade prop, carb is getting plenty of fuel (4 barrel) which the secondaries are opening, triming the drive around didn't help any. I did notice today that when cruising at 2800 rpms, and then pushing the throttle to WOT That the rpms from 2800 to about 3200 will jump up immediately which doesn't seem correct. Anyone have anymore ideas?

 

[Bondo]

Re: Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

Ayuh,.... Have ya read this yet,..??

 

[89cruisers]

Re: Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

I have gone through everything on that list, with the exception of the exhaust shutter, but it doesn't not seem to be clogging up

 

[Bondo]

Re: Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

Ayuh,... Have ya tried a smaller prop,..?? How'd it respond,..??

 

[Turn-n-Burn]

Re: Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

same OD as when new? wouldn't a 1.5 ratio be better?

 

[89cruisers]

Re: Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

Yes its still the same outdrive as new, have not tried a small pitch prop, I have a 13" which I was going to throw on, however the thrermostat housing was so rusted that it just cracked so now more waiting, any ideas until then?

 

[haulnazz15]

Re: Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

same OD as when new? wouldn't a 1.5 ratio be better?

The Nova 233 was a 351w with a 1.33 ratio drive. It was an oddball of sorts, since the same cubic inch SBC used the 1.5 ratio.

 

[haulnazz15]

Re: Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

Yes its still the same outdrive as new, have not tried a small pitch prop, I have a 13" which I was going to throw on, however the thrermostat housing was so rusted that it just cracked so now more waiting, any ideas until then?

Well keep in mind that 3800 is on the bottom edge of the acceptable WOT range for the 351w. I would try a different prop to see if you can pick up a few hundred rpms. 38mph seems on the slow side, but then again I haven't measured my boat with a GPS. I'd venture that with our 265HP 351w/233 drive, we are in the mid-upper 40's, I know we've hit 45 with the pitot-tube speedo, but I haven't checked accuracy.

 

[89cruisers]

Re: Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

well what pitch prop are you running? For a 16" which I have 3800 still seems a tad slow, especially since this engine has a 4 barrel, do you happen to know what you have your point gap set at? I'm going to look over that again today

 

[Gettinther]

Re: Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

well after new plugs and wires, and a new axle I took the nova out today. Wasn't able to get it to go above 3800rpms and got about 38mph out of it. It was suggested trim could have been off in the previous post, I move the trim all over the place and still never got above 3800 rpms and 38mph according to the gps. To go over again what's been done, had a 302 in the boat last year hooked up to a 233 drive which is a 1.3 ratio due to previous owner taking the factory 351 out and putting in the small 302 and was only getting up to about 3200 rpms. Put in the 351 this spring, new ignition (points rotor condenser wires plugs coil), which is advancing properly, good compression, 16 pitch 4 blade prop, carb is getting plenty of fuel (4 barrel) which the secondaries are opening, triming the drive around didn't help any. I did notice today that when cruising at 2800 rpms, and then pushing the throttle to WOT That the rpms from 2800 to about 3200 will jump up immediately which doesn't seem correct. Anyone have anymore ideas?

I would suggest Checking the tach for accuracy.
Where did the 351 come from ?
Is it a previous marine or auto?
New or experienced?
Marine cam or auto?

what is the dwell setting? - running
Is the carb jetted for the 351 or something else?
What carb is it ?
Again auto or marine?
Cam gears set at straight up or retarded ? early 351 is straight up / late 351 is 4deg. retarded, for this application I would set it straight up

In my opinion if the 302 would turn up 3200 rpm, the 351 should go 5000 on the same drive with the same prop in the same boat.

Some things to check and hope it helps.

 

[89cruisers]

Re: Wellcraft Nova Merc 233 (351W) Now not going above 3800rpms

It's a marine 351 out of a wellcraft, and the carb is set for the 351