Friend had a late 80's 25 Convincer with BB/Alpha. Same problem. He tried everything...props, tabs, Stern Jack. Nothing helped. He sold it before finding a solution. I think it was a hull issue.

I have a 88 28 checkmate. Mine will porpose at 3800 with no tab help. At 4200, it clears out if I dont use the tabs. I run a cleaver prop and have 550 hp. I can run it at 3300 rpms with the tabs down about 2 secs and the drive 1/4 the way up at about 40 mph. If you call checkmate, they will help you alot. They are very helpful. Good luck

Like we said above, change your prop! Your boat should not have a cleaver on it! Start with the Mirage+. If you can get on plane, then that will proably be your prop. If you can't plane with the Mirage, then try the Bravo 1. If the Bravo planes good, but doens't clean up the porpoise, then try the Hydromotive. My money is on the Mirage+ for you.

You might have got me confused with the person that started this thread, but I have to ask, why shouldnt my boat have a cleaver prop. I bought it like that and I have allways read that the cleaver is good for an older V-bottom boat. I am allways interested in learning. Thanks

Yep hook doesn't cause porpoising it actually helps get rid of it. My blackhawk had A LOT of rocker and it porpoised horribly at low speeds without the tabs.

And if I remember right Russ is running a Volvo DP so all the mentioned props won't work.

The tabs should help at cruise speeds. They will lift your stern enough and flatten the boat out and keep it on plane. You said you just got them so I'd keep playing with them.

No Boat is right I'm kinda stuck with props. I have a Volvo Dp drive. The boat had a OMC drive and it porposed with that set up also.

I posted this question on the Checkmate site but most of the guys get hurt feelings talking bad about a Checkmate. Some did try and help though. But it seems that most Checkmate convicors have this problem.

I dont have gauges on the tabs yet because I dont know if I'm going to sell the boat this winter. Is there a measurement to the tabs before I put the boat in the water again that might be close?

Your scareing me about hook and rocker!

I like the idea about adding weight to the bow. Would that make the boat un safe? Tell me more.

Like I said the boat is awsome at high speeds. Really fast and stable. No porpose and not chine walk at all. It makes me want to just add crazy HP and just cruize at 65 plus all the time. But that is kinda silly. But is the boat good at those speeds because of RPM's or the MPH?

Thanks
Russ

I've got an 87 251 Checkmate Convinsor. I had the same issue, very ssensitive to porpoising and Chine walking. I swapped out the Alpha for a Bravo ( left the same "X" ) but still had the same problems. Switched to a Hydromotive 4 Blade prop ( from a 3 blade Mirage ) and it drasticlly improved and became much easier to drive. I have an Imco 2" lower I want to try but have not gotten a chance yet.

Dave B

OK, not following you so help me by expaining a little more. Is the Mirage a bad prop for getting on plane? It's what I have, btw.

The Bravo 1 is different from the Mirage how? More stern lift? And how does the hydromotive rank?

For me, 2 factors are most critical - getting on plan with a minimum of nose lift and no proposing w/out having to stab down the tabs.

Same here. I have a 89 251, 502/Bravo setup. Did some prop testing and found that the Hydromotive 4 blades make a world of difference for porpoise compared to other brands 3 blades. I was told that the Hydromotive props give you a bit of stern lift and older Checkmates like that. I'm assuming stern lift helps keep the bow down at crusing speeds. Boat has run the best with a 24 Hydro so far. I have a 26p Hydro 4 blade that was too much pitch for my combo, but the boat handled just as good as the 24p. It's for sale if interested.

Was the X-dimension raised on the boat from the original dimension? This will cause the boat to porpoise.