Jim the new guy.

Well the shop say's they found both issues. (I haven't had it out on the lake yet thou).

The starter issue was a ground wire that had vibrated loose. They actaully said it was their fault - no charge. The high speed die problem, they say it was a spark plug boot that was almost off. They said that is the spark monitor system senses an 'Arc' (at high speed , high amp operation) then it would shut down the engine.

They tested the boat on a local lake an ran for 'over 5 minutes' at wide open throttle with no issues.
(I could not get more than a minute out of it before it died)

So - check your plug wires and I'm back to smiling again these days.

Thanks for the ideas and support everyone.

Jim

This is a good one....here are some possibilities suggested by a Tecnical Rep at Mercury Marine not in order of importance:

1) The alternator is weak and at higher RPM the battery draw is such that the electronics are shutting down.
2) The primary fuel pump is weak and at 5,500 RPM the engine starves and dies, this happens more with Optimax engines but is possible with the 240 EFI since they use the same basic block. It DOES tend to happen suddenly.
3) Back pressure in the exhaust will cause these symptoms as well. We have found the exhaust line collapsed at about that RPM if the earlier recall had not been done or wasn't done right. This is the recall done on all 2004 and earlier Merc engines.

We aren't a big fan of the Mercury either, they seem to work better in a Sugar Sand once you replace the primary fuel pump and fix the exhaust on the Optimax models. They were a necessary stepping stone in the evolution to the current design, we have some customers who bought 2000 models now with 700 hours and have never done anything but routine maintenance! Let us know if any of the things above make sense or work if you try them.

Kevin Seeber
Kingsland Marine

Interesting ideas. Last Monday my son had it out and it quit again (he said not at full speed) and it would no longer start but the starter would not kick in (just a quiet relay click you have to really listen for), they had to be towed off the lake Battery and everything else checks out so - it's in the shop. They are going to look at the 'just quits' issue as well as the starter. I'll give them your ideas as well. That recall item is very interesting, never heard of that ' exhaust line collapsed '. Your ideas all fit the boat's symptoms well.

Thanks for the info and ideas - I'll post what the shop finds.

keviseeb: There is fuel in the line. If it was a gas issue would it studder and die not just quit like someone turned off the key?

Utpoia Bill: Man that story stinks. It sounded like you found the issue but your repair place didn;t chase that lead... odd. I need to get an engine manual on this beast. Interesting that there is a low pressure fuel pump.

SO much to learn. I've living with the issue as it only happend when you run over 5500 RPM for a while, so I just crusie about at 40-45mph and avoid the issue. Thanks for the info.

At the risk of long distance diagnostics these symptoms sometimes occur because the ground from the engine to the battery is corroded. The engine gets hot and causes the ground to break, after it cools it miraculously fixes itself. Check the ground where it attaches to the engine from the battery. Even if it isn't loose clean it up anyway. Also make sure the battery posts are not loose on the battery. Did you have the throttle recall done?

Kevin Seeber
Kingsland Marine

Thanks for the suggestion - another thing to check. I understand the 'long distance diagnotics' part it's my issue to solve, just looking for ideas like your - thanks.

It's wierd that it starts right up again after it dies, no sputtering just turns off by itself. I think it has to be electrical. It may be some type of 'relay' (as mentioned earlier in the thread) that at high speed (and high RPMs) trips from an overload of some sort.

Had it out today and had it up to 50+ for a short time 20 seconds without a problem, crusied at 40+ for several minutes...

RIght now I'm living with it and checking ideas as they come up.

Send more ideas if you have any

Jim

Wish I had a suggestion, instead I have what sounds to be the same issue. (2001 Challenger 1800, 240HP M2 EFI).

My problem only happens at near to wide open throttle, below 40MPH I can run all day.

I'll also try what WAJetboating suggested when I get the boat back in the lake later this week. From my expierence it's like someone turned off the key - RPMs drop right to zero, starts right back up.

What/where is this relay you talked about?

Since this post was starting in June - what happened? Did you find the problem? share please if you did.