Put 15 hours of time on the boat while on vacation. Everything went great, except..

[Vettedrmr]

If you're interested, I put together a quick thread on our latest vacation to Lake Ouachita and our first extended use of our restored Tige, here:

https://www.tigeowners.com/forum/gen...-it-s-worth-it

Only had two real issues with the boat during the entire week. One is living without the center display, which prevents me from getting the speed control module rebuilt (no way to set the speed). Any suggestions (Tige tech support has helped me a bunch, but we're at a standstill) would be greatly appreciated.

The second is a few minor details concerning the engine. First off, there's a large dead-band (maybe 40+ degrees?) of throttle movement between forward gear engaging and any increase in engine power. Is there any way to adjust the throttle sensor to get rid of that dead-band? I'm thinking "No", because adjustment in the forward direction will affect the rear direction as well. Not a big issue, but was a surprise.

Second detail is more interesting. Engine start up, warm up, idle out to no wake zone is fine. Moderate throttle movement, where the rpm reasonably follows the throttle movement (after the dead band), is smooth and normal. But an aggressive movement, like pulling a skier up, will result in one or two backfires as the engine accelerates from idle, then smooths out and runs normally.

I had experienced this earlier on a test run, and tried retarding the timing (turning the distributor clockwise) a small amount, but it had little to no effect.

So, I wonder if this problem is fuel related. Could the injectors need to be replaced or rebuilt? As I mentioned, it runs fine once it gets past this initial transition, so none are clogged. But I wonder if the spray patterns are compromised.

Or could it be octane-related? I've been running the same fuel I've always run in my '96 La Brisa (5.8l PCM, carbureted), and both engines have essentially the same compression ratio.

Thanks in advance for any ideas, and have a good one,
Mike

[Vettedrmr]

boatwakes , I saw your response on the other ignition-related thread about setting the timing to 8^o BTDC in base timing mode. I searched and couldn't find anything about that procedure, except for using a Diacomm. 2 things: do you think my transient backfire is related to timing, or fuel? In any case I'd love to learn how to set my timing correctly, so if you could point me to that procedure I'd appreciate it.

Have a good one,
Mike

[boatwakes]

Hey Mike, we went through that on your previous thread and because you have the crab cap, the timing of yours is controlled by the computer requiring the distributor to be stabbed firing #1 within a few degrees of the timing mark on the balancer at TDC. The mercruiser engines with thunderbolt and Delco ignition are at 8* BTDC and this procedure is done using the DTC computer or looping the MEFI 3 connector to take the ignition module preset timing curve out of the equation. Again, with the crab cap, there is no timing set procedure and instead the distributor must be installed firing at 1 at firing TDC on the balancer timing mark. A backfire means the intake valve is open when spark is introduced sooooooo either the computer is misreading throttle input (highly likely after reading you have a dead spot in the throttle) or the ECM is fluctuating timing. It sounds like it's repeatable so I'd say put a timing light on the system and watch what it does when the situation occurs.

[Vettedrmr]

Ah, now I understand why I didn't know what the base timing mode was. We've just about recovered from 10 straight days on the lake (well, there was one day off), so I'll work with it some more and let you know what happens.

Any ideas about the dead spot in the throttle sensor? I'm going to try to get some video of it next time we go out.

Thanks for all your help, and have a good one,
Mike