I guess a quick intro is in order... I'm a convert. from years of outboards to my second I/O Checkmate, and I'm not looking back. I spend allot of time on the Checkmate forums, but thought I'd ask these questions here to see what others thought. I have a 92 Checkmate Persuader 234 with a 454 Mag that has been massaged mildly to nearly 400hp. I got it in October of last year and for the most part it runs very well. It developed a soft miss (no backfire or popping)at various rpms and temps. Just about everything has been replaced, and i mean everything. I suspect either a wiring issue now or an internal motor problem.
Well, suffice it to say, this fall the motor is coming out as is the fuel tank. Here are my questions:

#1 I have the typical Merc raw water/fuel pump set-up. I want to go to a return style electric system as that's what I built for my 740hp Camaro, and it works well. Any thoughts good or bad to this? What brand of regulator and pump did you use?

#2 I'd like to lose the Thunderbolt4 ignition and go with an MSD set-up. I don't plan any major engine mods other than heads, cam and headers, so i don't need to go nuts here. Suggestions as to what to use? Is it worth it?

#3 I have an interesting exhaust set-up. From the factory, checkmate had an option for the 4 inch pipes to come out through the transom and under the waterline at no wake speeds. Basically it's quiet while idling around, but then barks on plane. I like this esp. when towing small kids on a tube just off idle. I'm planning on upgrading to hi-po manifolds or headers but am unsure which way to go. They are allot of $$$ so maybe manifolds are going to allow me to spend the extra $$$ elsewhere. What are your thoughts on this? Can they work with below waterline pipes?

sorry for the length of this, just figured i'd get it all out at once.

#1 Unless you are going to bump the HP over 575-600hp, then the stock fuel pump is plenty. No reason to go electric with a return, especially for a carbed engine.

#2 The TB IV is a very good system and is much more reliable than an MSD. Just chnage to a V8-HP module or V6 module.

#3 You will probably have to get custom risers or tailpipes made.

Thanks for the reply. Is there any disadvantage to doing an electric fuel system with return other than cost? With fuel and ignition, i'm basically trying to duplicate what i've done with my 69 camaro and that is the one toy that has been perfectly reliable, which is more than i can say with my boat I'll take it into consideration though, leaving it all as is.

Hi Rolf, Welcome. You already know my answers, Most repeated here already.. lol Jamie / Lakeside

Jamie, are you stalking me? LOL, yeah... i know the answers from most ppl and they all echo the same thing.... leave it be! Here's a guy who wants to spend some coin for some good stuff but keeps getting talked out of it! FWIW Jamie, I tuned the carb one stage richer last night and am running it tomorrow with some tools and a compression gauge. We'll see what that accomplishes. I'm really preparing to just go nuts and get it all done, but i have a jeep tj, a dump truck, a mustang cobra clone, a vw jetta and other toys to sell first. Not that i couldnt do it first, but i'd rather not use a credit card outright .

You say it has a "soft miss"

I would suspect a valve train issue. I highly doubt it has anything to with the ignition or fuel pump delivery.

The merc fuel pump and TB IV are about as reliable you can get. If you up the HP, I would just change the ignition module which will change the timing curve.

Thanks for the reply Griff. It's hard to describe, the miss that is. It's noticable but there is no noise assoc. with it. Yup, fuel pressure and volume are OK with the stock pump. Well, we'll see after tomorrow night what direction i'm going in. Thanks again.

I went with an electric pump on my 454 mag after I discovered the cam on the raw water pump was wiped(no fluid in it). I went with a free holley projection pump I got off a friend and installed it with a holley bypass regulator. I piped the return back into the extra inlet port or my water fuel seperator as an easy short term solution. The better solution would be to pipe it back to the tank for a fresh supply of cool fuel. This can be done with a tee you can cut into the fuel fill hose. Danger though, do not use the sea pump without a fuel pump mounted on it as it can cause the bearing on the cam to wear out and lodge itself inside the case seizing the pump.