4.3 only making 2300 RPM under load

[ChadTiffin]

So we're trying to revive an 18' 97 Coral Sunseeker with a 4.3 Penta that's been sitting in the bushes for the last 8 yrs. It never ran well which is why it ended up in neglect, but we're making an effort to get it going now.

After rebuilt starter, new impeller, new plugs, cleaned distributor cap, new oil in both sections it starts up almost instantly and seems to run very smoothly and revs fine in the driveway. We put it in the water today and RPM maxed out at 2300 RPM WOT, barely got it up on plane with only 2 of us onboard, and maxed out at 29 mph.

Any ideas? As I said it seems to run beautifully in the driveway, but under load has no power. I've got a new distributor cap on order but I have a hard time believing that's enough to lose that much power. Also compressions were 180/195/187/160/160/172.

 

[alldodge]

Basics
Plugs MR43T gap at .035
Timing TB-IV 8 BTDC for TB-V 10 BTDC

Take your timing light and when running place it one by one on each plug wire to see if they are firing. If that checks out pull them off one at a time to see if there are any changes. Do this under a medium load

 

[ChadTiffin]

Ok thanks, I already pulled the sparkplugs out one at a time and cranked the engine, they all had spark. But we'll try pulling the leads while its running and see what happens.

 

[Maclin]

Just trying to reconcile the RPM and MPH numbers of 2300pm at 29mph, something is a little off, to be able to do this you need a 25pitch prop. So Tach or Speedo (or both) is off a bit.

Just seems to me the timing may need a look-see. There is a shunt tool needed and specific timing sequence to follow for this '97 Volvo Penta.

 

[Maclin]

Well heck, might as well ask.. What pitch is your prop?