2 suggestions Two things, I can think of: The Rhoads lifters you mentioned, may not be pumping up to give you the top end. or Could it be a fuel problem because of carb mounting angle at speed. Have you tried angled spacers? Tom
I have been around boats all my life. Lots of experience with direct drive inboards, and outboards, not much with jets because they stink as water ski boats. As I understand it a jet drive is basically a prop (impeller) in a tube. The prop acts like a torque converter. Running 55 mph at 3700 means you have a fast hull. (My Nautique runs 45 mph at 4600 rpm, designed for skiing not speed.) Since you say low speed is it good does not sound like a big mismatch with the pump setup. Exhaust looks pretty good. You have good rise on the header and I expect it feeds into a 3 inch pipe with pump water dumped in somewhere. This is a very good system and should cause no problems. The question for me is why does your motor need so much timing? I know that marine motors (the non computerized versions) are very conservative on timing. You should have no problems running 30 to 32 degrees of total advance. What is your initial timing and how much advance is in the distributor?
Maybe this will help, go over an talk to these guy's........http://www.realoldspower.com/phpBB2/viewforum.php?f=7
I did not degree the cam but it is a roll master double roller. The secondaries are opening all the way. I had the spring tight and loosened it off and are too loose now. If I can get the rpm 's up higher I might have to roll off the timing a bit but at that lower rpm it can handle it. I've also had the pistons ceramic coated they told me it was good for reflecting the heat away from the piston. That would allow for a little more timing as well I think. I have the the lightest set of springs in the distributor and have welded the mechanical so not to get the full sweep of the weights. The exhaust is 3.5" pipe into 3.5" rubber hose thru transum. I think the stock intake is the weakest link in the motor now. I'm going to put SP1 on this spring and see what happens!! :beer Thanks for those other sites lots of good information on there too!!
HP vs TQ A B4B intake will make plenty of power past 3700 RPM. I am inclined to think the problem lies in the pump/drive setup. I would tend to think a healthy BBB should be able to have pleanty enough oats to drive a boat past 55 mph, no matter how the pump is set up, though. The motor/drive combo must be mismatched somehow (maybe pumps which are good for being quick off the line end up fighting themselves at certain RPM's instead of providing more foward thrust, which could be locking you down). At any rate, a SP1 is a higher RPM piece and I think it will only make things worse at 3700. Good Luck
Degree the Cam! Landshark, you need to degree the cam. I have heard of many cases where the roll master timing sets were off. HTH!
